Revised Standards for Hazardous Waste Combustors
[Federal Register: April 19, 1996 (Volume 61, Number 77)]
[Proposed Rules]
[Page 17357-17407]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr19ap96-27]
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Parts 60, 63, 260, 261, 264, 265, 266, 270, and 271
[FRL-5447-2]
RIN 2050-AF01
Revised Standards for Hazardous Waste Combustors
AGENCY: Environmental Protection Agency.
ACTION: Proposed rule.
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SUMMARY: The Agency is proposing revised standards for hazardous waste
incinerators, hazardous waste-burning cement kilns, and hazardous
waste-burning lightweight aggregate kilns. These standards are being
proposed under joint authority of the Clean Air Act (CAA) and Resource
Conservation and Recovery Act (RCRA). The standards limit emissions of
chlorinated dioxins and furans, other toxic organic compounds, toxic
metals, hydrochloric acid, chlorine gas, and particulate matter. These
standards reflect the performance of Maximum Achievable Control
Technologies (MACT) as specified by the Clean Air Act. The MACT
standards also should result in increased protection to human health
and the environment over existing RCRA standards. The nature of this
proposal requires that the following actions also be proposed:
proposing the addition of hazardous waste-burning lightweight aggregate
kilns to the list of source categories in accordance with 112(c)(5) of
the Act; exempting from RCRA emission controls secondary lead
facilities subject to MACT; considering an exclusion for certain
``comparable fuels''; and revising the small quantity burner exemption
under the BIF rule.
DATES: EPA will accept public comments on this proposed rule until June
18, 1996.
ADDRESSES: Commenters must send an original and two copies of their
comments referencing docket number F-96-RCSP-FFFFF to: RCRA Docket
Information Center, Office of Solid Waste (5305W), U.S. Environmental
Protection Agency Headquarters (EPA, HQ), 401 M Street, SW.,
Washington, DC 20460. Deliveries of comments should be made to the
Arlington, VA, address listed below. Comments may also be submitted
electronically through the Internet to: RCRA-Docket@epamail.epa.gov.
Comments in electronic format should also be identified by the docket
number F-96-RCSP-FFFFF. All electronic comments must be submitted as an
ASCII file avoiding the use of special characters and any form of
encryption.
Commenters should not submit electronically any Confidential
Business Information (CBI). An original and two copies of CBI must be
submitted under separate cover to: RCRA CBI Document Control Officer,
Office of Solid Waste (5305W), U.S. EPA, 401 M Street, SW, Washington,
DC 20460.
Public comments and supporting materials are available for viewing
in the RCRA Information Center (RIC), located at Crystal Gateway One,
1235 Jefferson Davis Highway, First Floor, Arlington, VA. The RIC is
open from 9 a.m. to 4 p.m., Monday through Friday, excluding federal
holidays. To review docket materials, the public must make an
appointment by calling (703) 603-9230. The public may copy a maximum of
100 pages from any regulatory docket at no charge. Additional copies
cost $.15/page. The index and some supporting materials are available
electronically. See the ``Supplementary Information'' section for
information on accessing them.
A public hearing will be held, if requested, to discuss the
proposed standards for hazardous waste combustors, in accordance with
section 307(d)(5) of the Act. Persons wishing to make an oral
presentation at a public hearing should contact the EPA at the address
given in the ADDRESSES section of this preamble. Oral presentations
will be limited to 5 minutes each, unless additional time is feasible.
Any member of the public may file a written statement before, during,
or within 30 days after the hearing. Written statements should be
addressed to the RCRA Docket Section address given in the ADDRESSES
section of this preamble and should refer to Docket No. F-96-RCSP-
FFFFF. A verbatim transcript of the hearing and written statements will
be available for public inspection and copying during normal working
hours at the EPA's RCRA Docket Section in Washington, D.C. (see
ADDRESSES section of this preamble).
FOR FURTHER INFORMATION CONTACT: For general information, contact the
RCRA Hotline at 1-800-424-9346 or TDD 1-800-553-7672 (hearing
impaired). In the Washington metropolitan area, call 703-412-9810 or
TDD 703-412-3323.
For more detailed information on specific aspects of this
rulemaking, contact Larry Denyer, Office of Solid Waste (5302W), U.S.
Environmental Protection Agency, 401 M Street, SW., Washington, DC
20460, (703) 308-8770, electronic mail: Denyer.Larry@epamail.epa.gov.
For more detailed information on implementation of this rulemaking,
contact Val de la Fuente, Office of Solid Waste (5303W), U.S.
Environmental Protection Agency, 401 M Street, SW., Washington, DC
20460, (703) 308-7245, electronic mail: DeLaFuente.Val@epamail.epa.gov.
For more detailed information on regulatory impact assessment of this
rulemaking, contact Gary Ballard, Office of Solid Waste (5305), U.S.
Environmental Protection Agency, 401 M Street, SW., Washington, DC
20460, (202) 260-2429, electronic mail: Ballard.Gary@epamail.epa.gov.
For more detailed information on risk analyses of this rulemaking,
contact David Layland, Office of Solid Waste (5304), U.S. Environmental
Protection Agency, 401 M Street, SW., Washington, DC 20460, (202) 260-
4796, electronic mail: Layland.David@epamail.epa.gov.
SUPPLEMENTARY INFORMATION: The index and the following supporting
materials are available on the Internet: (List documents) Follow these
instructions to access the information electronically:
Gopher: gopher.epa.gov
WWW: http://www.epa.gov
Dial-up: (919) 558-0335.
This report can be accessed off the main EPA Gopher menu, in the
directory: EPA Offices and Regions/Office of Solid Waste and Emergency
Response (OSWER)/Office of Solid Waste (RCRA)/(consult with
Communication Strategist for precise subject heading)
FTP: ftp.epa.gov
Login: anonymous
Password: Your Internet address
Files are located in /pub/gopher/OSWRCRA
The official record for this action will be kept in paper form.
Accordingly, EPA will transfer all comments received electronically
into paper form and place them in the official record, which will also
include all comments submitted directly in writing. The official record
is the paper record maintained at the address in ADDRESSES at the
beginning of this document.
EPA responses to comments, whether the comments are written or
electronic, will be in a notice in the Federal Register or in a
response to comments document placed in the official record for this
rulemaking. EPA will not immediately reply to commenters electronically
other than to seek clarification of electronic comments that may be
garbled in transmission or during conversion to paper form, as
discussed above.
Glossary of Acronyms
APCD--Air Pollution Control Device
[[Page 17359]]
BDAT--Best Demonstrated Available Technology
BIFs--Boilers and Industrial Furnaces
BTF--Beyond-the-Floor
CAA--Clean Air Act
Cl2--Chlorine
CO--Carbon Monoxide
D/F--Dioxins/Furans
D/O/M--Design/Operation/Maintenance
ESP--Electrostatic Precipitator
EU--European Union
FF--Fabric Filter
HAP--Hazardous Air Pollutant
HC--Hydrocarbons
HCl--Hydrochloric acid
Hg--Mercury
HHE--Human Health and the Environment
HON--Hazardous Organic NESHAPs
HSWA--Hazardous and Solid Waste Amendments
HWC--Hazardous Waste Combustion/Combustor
ICR--Information Collection Request
LDR--Land Disposal Restrictions
LVM--Low-volatile Metals
LWAK--Lightweight Aggregate Kiln
MACT--Maximum Achievable Control Technology
MTEC--Maximum Theoretical Emission Concentration
NESHAPs--National Emission Standards for Hazardous Air Pollutants
PM--Particulate Matter
PICs--Products of Incomplete Combustion
RCRA--Resource Conservation and Recovery Act
RIA--Regulatory Impact Assessment
SVM--Semivolatile Metals
TCLP--Toxicity Characteristic Leaching Procedure
UTS--Universal Treatment Standards
Part One: Background
I. Overview
II. Relationship of Today's Proposal to EPA's Waste Minimization
National Plan
Part Two: Devices That Would Be Subject To The Proposed Emission
Standards
I. Hazardous Waste Incinerators
A. Overview
B. Summary of Major Incinerator Designs
C. Number of Incinerator Facilities
D. Typical Emission Control Devices For Incinerators
II. Hazardous Waste-Burning Cement Kilns
A. Overview of Cement Manufacturing
B. Summary of Major Design and Operating Features of Cement
Kilns
C. Number of Facilities
D. Emissions Control Devices
III. Hazardous Waste-Burning Lightweight Aggregate Kilns
A. Overview of Lightweight Aggregate Kilns (LWAKs)
B. Major Design and Operating Features
C. Number of Facilities
D. Air Pollution Control Devices
Part Three: Decision Process for Setting National Emission Standards
for Hazardous Air Pollutants (NESHAPs)
I. Source of Authority for NESHAP Development
II. Procedures and Criteria for Development of NESHAPs
III. List of Categories of Major and Area Sources
A. Clean Air Act Requirements
B. Hazardous Waste Incinerators
C. Cement Kilns
D. Lightweight Aggregate Kilns
IV. Proposal to Subject Area Sources to the NESHAPs under
Authority of Section 112(c)(6)
V. Selection of MACT Floor for Existing Sources
A. Proposed Approach: Combined Technology-Statistical Approach
B. Another Approach Considered But Not Used
C. Identifying Floors as Proposed in CETRED
D. Establishing Floors One HAP or HAP Group at a Time
VI. Selection of Beyond-the-Floor Levels for Existing Sources
VII. Selection of MACT for New Sources
VIII. RCRA Decision Process
A. RCRA and CAA Mandates to Protect Human Health and the
Environment
B. Evaluation of Protectiveness
C. Use of Site-Specific Risk Assessments under RCRA
Part Four: Rationale for Selecting the Proposed Standards
I. Selection of Source Categories and Pollutants
A. Selection of Sources and Source Categories
B. Selection of Pollutants
C. Applicability of the Standards Under Special Circumstances
II. Selection of Format for the Proposed Standards
A. Format of the Standard
B. Averaging Periods
III. Incinerators: Basis and Level for the Proposed NESHAP
Standards for New and Existing Sources
A. Summary of MACT Standards for Existing Incinerators
B. Summary of MACT Standards For New Incinerators
C. Evaluation of Protectiveness
IV. Cement Kilns: Basis and Level for the Proposed NESHAP
Standards for New and Existing Sources
A. Summary of Standards for Existing Cement Kilns
B. MACT for New Hazardous Waste-Burning Cement Kilns
C. Evaluation of Protectiveness
V. Lightweight Aggregate Kilns: Basis and Level for the Proposed
NESHAP Standards for New and Existing Sources
A. Summary of MACT Standards for Existing LWAKs
B. MACT for New Sources
C. Evaluation of Protectiveness
VI. Achievability of the Floor Levels
VII. Comparison of the Proposed Emission Standards With Emission
Standards for Other Combustion Devices
VIII. Alternative Floor (12 Percent) Option Results
A. Summary of Results of 12 Percent Analysis
B. Summary of MACT Floor Cost Impacts and Emissions Reductions
C. Alternative Floor Option: Percent Reduction Refinement
IX. Additional Data for Comment
Part Five: Implementation
I. Selection of Compliance Dates
A. Existing Sources
B. New Sources
C. One year extensions for Pollution Prevention/Waste
Minimization
II. Selection of Proposed Monitoring Requirements
A. Monitoring Hierarchy
B. Use of Comprehensive Performance Test Data to Establish
Operating Limits
C. Compliance Monitoring Requirements
D. Combustion Fugitive Emissions
E. Automatic Waste Feed Cutoff (AWFCO) Requirements and
Emergency Safety Vent (ESV) Openings
F. Quality Assurance for Continuous Monitoring Systems
III. MACT Performance Testing and Related Issues
A. MACT Performance Testing
B. RCRA Trial Burns
C. Waiver of MACT Performance Testing for HWCs Feeding De
Minimis Levels of Metals or Chlorine
D. Relative Accuracy Tests for CEMS
IV. Selection of Manual Stack Sampling Methods
V. Notification, Recordkeeping, Reporting, and Operator
Certification Requirements
A. Notification Requirements
B. Reporting Requirements
C. Recordkeeping Requirements
VI. Permit Requirements
A. Coordination of RCRA and CAA Permitting Processes
B. Permit Application Requirements
C. Clarifications on Definitions and Permit Process Issues
D. Pollution Prevention/Waste Minimization Options
E. Permit Modifications Necessary to Come Into Compliance With
MACT Standards
VII. State Authorization
A. Authority for Today's Rule
B. Program Delegation Under the Clean Air Act
C. RCRA State Authorization
VIII. Definitions
A. Definitions Proposed in Sec. 63.1201
B. Conforming Definitions Proposed in Secs. 260.10 and 270.2
C. Clarification of RCRA Definition of Industrial Furnace
Part Six: Miscellaneous Provisions and Issues
I. Comparable Fuel Exclusion
A. EPA's Approach to Establishing Benchmark Constituent Levels
B. Sampling, Analysis, and Statistical Protocols Used
C. Options for the Benchmark Approach
D. Comparable Fuel Specification
E. Exclusion of Synthesis Gas Fuel
F. Implementation of the Exclusion
G. Transportation and Storage
H. Speculative Accumulation
I. Regulatory Impacts
II. Miscellaneous Revisions to the Existing Rules
A. Revisions to the Small Quantity Burner Exemption under the
BIF Rule
B. The Waiver of the PM Standard under the Low Risk Waste
Exemption of the
[[Page 17360]]
BIF Rule Would Not Be Applicable to HWCs
C. The ``Low Risk Waste'' Exemption from the Emission Standards
Provided by the Existing Incinerator Standards Would Be Superseded
by the MACT Rules
D. Bevill Residues
E. Applicability of Regulations to Cyanide Wastes
F. Shakedown Concerns
G. Extensions of Time Under Certification of Compliance
H. Technical Amendments to the BIF Rule
I. Clarification of Regulatory Status of Fuel Blenders
J. Change in Reporting Requirements for Secondary Lead Smelters
Subject to MACT
Part Seven: Analytical and Regulatory Requirements
I. Executive Order 12866
II. Regulatory Options
III. Assessment of Potential Costs and Benefits
A. Introduction
B. Analysis and Findings
C. Total Incremental Cost per Incremental Reduction in HAP
Emissions
D. Human Health Benefits
E. Other Benefits
IV. Other Regulatory Issues
A. Environmental Justice
B. Unfunded Federal Mandates
C. Regulatory Takings
D. Incentives for Waste Minimization and Pollution Prevention
V. Regulatory Flexibility Analysis
VI. Paperwork Reduction Act
VII. Request for Data
Appendix--Comparable Fuel Constituent and Physical Specifications
PART 60--STANDARDS OF PERFORMANCE FOR NEW STATIONARY SOURCES
PART 63--NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS
FOR SOURCE CATEGORIES
PART 260--HAZARDOUS WASTE MANAGEMENT SYSTEM: GENERAL
PART 261--IDENTIFICATION AND LISTING OF HAZARDOUS WASTE
PART 264--STANDARDS FOR OWNERS AND OPERATORS OF HAZARDOUS WASTE
TREATMENT, STORAGE, AND DISPOSAL FACILITIES
PART 265--INTERIM STATUS STANDARDS FOR OWNERS AND OPERATORS OF
HAZARDOUS WASTE TREATMENT, STORAGE, AND DISPOSAL FACILITIES
PART 266--STANDARDS FOR THE MANAGEMENT OF SPECIFIC HAZARDOUS WASTES
AND SPECIFIC TYPES OF HAZARDOUS WASTE MANAGEMENT FACILITIES
PART 270--EPA ADMINISTERED PERMIT PROGRAMS: THE HAZARDOUS WASTE
PERMIT PROGRAM
PART 271--REQUIREMENTS FOR AUTHORIZATION OF STATE HAZARDOUS WASTE
PROGRAMS
PART ONE: BACKGROUND
I. Overview
The U.S. Environmental Protection Agency (EPA) is proposing to
revise standards for hazardous waste incinerators and hazardous waste-
burning cement kilns and lightweight aggregate kilns (LWAKs) under
joint authority of the Clean Air Act, as amended, (CAA) and the
Resource Conservation and Recovery Act, as amended (RCRA). The emission
standards in today's proposal have been developed under the CAA
provisions concerning the maximum level of achievable control over
hazardous air pollutants (HAPs), taking into consideration the cost of
achieving the emission reduction, any non-air quality health and
environmental impacts, and energy requirements. These maximum
achievable control technology (MACT) standards, also referred to as
National Emission Standards for Hazardous Air Pollutants (NESHAPs), are
proposed in today's rule for the following HAPs: dioxins/furans,
mercury, two semivolatile metals (lead and cadmium), four low
volatility metals (antimony, arsenic, beryllium, and chromium),
particulate matter, and hydrochloric acid/chlorine gas. Other toxic
organic emissions are addressed by standards for carbon monoxide (CO)
and hydrocarbons (HC).
This action is being taken for several reasons. First, this
proposal is consistent with the terms of the 1993 settlement agreement
between the Agency and a number of groups who challenged EPA's final
RCRA rule entitled ``Burning of Hazardous Waste in Boilers and
Industrial Furnaces'' (56 FR 7134, Feb. 21, 1991). These groups include
the Natural Resources Defense Council, Sierra Club, Inc., Hazardous
Waste Treatment Council (now the Environmental Technology Council),
National Solid Waste Management Association, and a number of local
citizens' groups. Under this settlement agreement, the Agency is to
propose this rulemaking by September-November, 1995, and finalize it by
December 1996.
Second, EPA has scheduled rulemakings to develop maximum achievable
control technology (MACT) standards for hazardous waste incinerators
and cement kilns. To minimize the burden on the Agency and the
regulated community, the Agency has combined its efforts under the CAA
and RCRA into one rulemaking to establish MACT standards, which also
would satisfy the RCRA settlement agreement obligations.
Third, the Agency's Hazardous Waste Minimization and Combustion
Strategy, first announced in May 1993, in addition to stressing waste
minimization, also made a commitment to upgrade the emission standards
for hazardous waste-burning facilities. The three categories of
facilities covered in this proposal burn over 80 percent of the total
amount of hazardous waste being combusted each year. [The remaining 15-
20 percent is burned in industrial boilers and other types of
industrial furnaces, which are to be addressed in the next rulemaking
for which a proposal is to be issued by December 1998 or sooner.]
Finally, as relates to the development of revised standards under
concurrent Clean Air Act and RCRA authority, most of these hazardous
waste combustion facilities are major sources of HAP emissions. They
therefore must be regulated under section 112(d) of the Clean Air Act.
In addition, EPA noted, when promulgating the RCRA rules for boilers
and industrial furnaces in 1991 and in a proposal to revise the
incinerator rules, that existing standards did not fully consider the
possibility of exposure via indirect (non-inhalation) exposure
pathways. 56 FR at 7150, 7167, 7169-70 (Feb. 21, 1991); 54 FR at 43720-
21, 43723, 43757 (Oct. 26, 1989). The Agency reiterated these concerns
in the Combustion Strategy announced in 1993 as one of the major
factors leading to its decision to undertake revisions to the standards
for hazardous waste combustors. As also noted in the Combustion
Strategy and elsewhere, site-specific RCRA omnibus authority, whereby
permit writers can impose additional conditions as are necessary to
protect human health and the environment, can be used to buttress the
existing regulations. See, e.g., 56 FR 7145, at n.8. Nevertheless, this
process is expensive, time-consuming, and not always sufficiently
certain in result. The Agency thus indicated, in the Combustion
Strategy, that technology-based standards could provide a superior
means of control by providing certainty of operating performance.
Because of the joint authorities under which this rule is being
proposed, the proposal also contains an implementation scheme that is
intended to harmonize the RCRA and CAA programs to the maximum extent
permissible by law. In pursuing a common-sense approach towards this
objective, the proposal seeks to establish a framework that: (1)
Provides for combined (or at least coordinated) CAA and RCRA permitting
of these facilities; (2) allows maximum flexibility for regional,
state, and local agencies to determine which of their resources will be
used for permitting, compliance, and enforcement efforts; and (3)
integrates the monitoring, compliance testing, and recordkeeping
requirements of the CAA and RCRA so that facilities will be able
[[Page 17361]]
to avoid two potentially different regulatory compliance schemes.
In addition, this proposal addresses the variety of issues, to the
extent appropriate at this time, raised in several petitions filed with
the Agency. These petitions are from the Cement Kiln Recycling
Coalition (Jan. 18, 1994), the Hazardous Waste Treatment Council (May
18, 1994), and the Chemical Manufacturers Association (Oct. 14, 1994).
II. Relationship of Today's Proposal to EPA's Waste Minimization
National Plan
EPA believes that today's proposed rule will create significant
incentives for source reduction and recycling by waste generators that
would, in turn, help facilities achieve compliance with the MACT
standards. RCRA, as well as the Pollution Prevention Act of 1990 (PPA),
encourage pollution prevention at the source, and the Clean Air Act
mentions pollution prevention as a specific means of achieving MACT. In
Sec. 112(d)(2) of the CAA, Congress expressly defined MACT as the
``application of measures, processes, methods, systems, or techniques
including, but not limited to, measures which reduce the volume of, or
eliminate emissions of, such pollutants through process changes,
substitution of materials and other modifications.''
In addition, in the Hazardous and Solid Waste Amendments of 1984
(HSWA) to RCRA, Congress established a national policy for waste
minimization. Section 1003 of RCRA states that, whenever feasible, the
generation of hazardous waste is to be reduced or eliminated as
expeditiously as possible. Section 8002(r) requires EPA to explore the
desirability and feasibility of establishing regulations or other
incentives or disincentives for reducing or eliminating the generation
of hazardous waste. In 1990, the PPA reinforced these policies by
declaring it ``to be the national policy of the United States that
pollution should be prevented at the source whenever feasible'' and,
when not feasible, waste should be recycled, treated, or disposed of--
in that order of preference.
Although the Agency has devoted significant effort to evaluation
and promotion of waste minimization in the past 1, the Hazardous
Waste Minimization and Combustion Strategy, first announced in May
1993, recently provided a new impetus to this effort. The Strategy had
several components, among which was reducing the amount and toxicity of
hazardous waste generated in the United States. Other components of the
Strategy included strengthening controls on emissions from hazardous
waste combustion units; enhancing public participation in facility
permitting; establishing risk assessment policies with respect to
facility permitting; and continued emphasis on strong compliance and
enforcement.
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\1\ For example, EPA prepared a report to Congress,
``Minimization of Hazardous Wastes'' (October 1986), that summarized
existing waste minimization activities and evaluated options for
promoting waste minimization.
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EPA held a National Roundtable and four Regional Roundtables
throughout the nation in 1993-94 to facilitate a broad dialogue on the
spectrum of waste minimization and combustion issues. The major
messages from these Roundtables became the building blocks for EPA's
further efforts to promote source reduction and recycling and
specifically for EPA's Waste Minimization National Plan, released in
November 1994.
The Waste Minimization National Plan focuses on the goal of
reducing persistent, bioaccumulative, and toxic constituents in
hazardous waste nationally by 25 percent by the year 2000 and 50
percent by the year 2005. The central themes of the National Plan are:
(1) Developing a framework for setting national priorities for the
minimization of hazardous waste; (2) promoting multimedia environmental
benefits and preventing cross-media transfers; (3) demonstrating a
strong preference for source reduction by shifting attention to
hazardous waste generators to reduce generation at its source; (4)
defining and tracking progress in minimizing the generation of wastes;
and (5) involving citizens in waste minimization implementation
decisions. The Agency intends to continue its pursuit of hazardous
waste minimization under the National Plan and other Agency initiatives
in concert with the actions proposed in today's rule.
Of the 3.0 million tons of hazardous waste combusted in 1991,
approximately two-thirds of that amount were combusted at on-site
facilities (i.e., the same facilities at which the waste was
generated). Combustion at an on-site facility therefore presents a
situation in which the same facility owners and operators may have some
measure of control over generation of wastes at its source and its
ultimate disposition. Although close to 400 industries generated wastes
destined for combustion in 1991, much of the quantity was concentrated
in a few sectors. As a companion to this proposed rule, EPA is focusing
its waste minimization efforts on reducing the generation and
subsequent release to the environment of the most persistent,
bioaccumulative, and toxic constituents in hazardous wastes (i.e.,
metals, halogenated organics).
Analysis of waste minimization potential suggests that generators
currently burning wastes may have a number of options for eliminating
or reducing these wastes. We believe that roughly 15 percent of all
combusted wastes may be amenable to waste minimization. Three waste
generating processes appear to have the most potential in terms of
tonnage reduction: (1) Solvent and product recovery/distillation
procedures, primarily in the organic chemicals industry, (2) product
processing wastes, and (3) process waste removal and cleaning. In
addition, preliminary analyses of Toxics Release Inventory and
hazardous waste stream data indicate that over 3 million pounds of
hazardous metals are contained in waste streams being combusted. The
top 5 ranking metals (with respect to health risk considering
persistence, bioaccumulation, and toxicity) are mercury, cadmium, lead,
copper, and selenium. Additional analyses are underway to identify the
industry sectors and production processes that are chief sources of
these and other high priority hazardous constituents.2
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\2\ USEPA, Office of Solid Waste, ``Setting Priorities for
Hazardous Waste Minimization'', July 1994.
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In today's rule, EPA is soliciting comment on two options to
promote the use of pollution prevention/waste minimization measures as
methods for helping meet MACT standards. These options (regarding feed
stream analysis and permitting requirements) are described in Part
Five, Section VI, Subsection D of this preamble. EPA is also seeking
comment on a proposal to consider, on a case-by-case basis, extending
the compliance deadlines for this rule by one year if a facility can
show that extra time is needed to implement pollution prevention/waste
minimization measures in order for the facility to meet the MACT
standards and that implementation cannot be practically achieved within
the allotted three-year period after promulgation of this rule (see
Part V, Section 1, Subsection C).
PART TWO: DEVICES THAT WOULD BE SUBJECT TO THE PROPOSED EMISSION
STANDARDS
I. Hazardous Waste Incinerators
A. Overview
A hazardous waste incinerator is an enclosed, controlled flame
combustion
[[Page 17362]]
device, as defined in 40 CFR 260.10, and is used to treat primarily
organic and/or aqueous wastes. These devices may be in situ (fixed), or
consist of mobile units (such as those used for site remediation and
superfund clean-ups) or may consist of units burning spent or unusable
ammunition and/or chemical agents that meet the incinerator definition.
B. Summary of Major Incinerator Designs
The following is a brief description of the typical incinerator
designs used in the United States.3
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\3\ For a more detailed description of incineration technology,
see ``Combustion Emissions Technical Resource Document (CETRED)'',
USEPA EPA530-R-94-014, May 1994.
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1. Rotary Kilns
Rotary kiln systems typically contain two incineration chambers:
the rotary kiln and an afterburner. The kiln itself is a cylindrical
refractory-lined steel shell 10-20 feet in diameter, with a length-to-
diameter ratio of 2 to 10. The shell is supported by steel trundles
that ride on rollers, allowing the kiln to rotate around its horizontal
axis at a rate of 1-2 revolutions per minute. Wastes are fed directly
at one end of the kiln and heated by primary fuels. Waste continues to
heat and burn as it travels down the inclined kiln. Combustion air is
provided through ports on the face of the kiln. The kiln typically
operates at 50-200 percent excess air and temperatures of 1600-
1800 deg.F. Flue gas from the kiln is routed to an afterburner
operating at 2000-2500 deg.F and 100-200 percent excess air where
unburnt components of the kiln flue gas are more completely combusted.
Auxiliary fuel and/or pumpable liquid wastes are typically used to
maintain the afterburner temperature.
Some rotary kiln incinerators, known as slagging kilns, operate at
high enough temperatures such that residual materials leave the kiln in
a molten slag form. The molten residue is then water-quenched. Another
kiln, an ashing kiln, operates at a lower temperature, producing a
residual ash, which leaves as a dry material.
2. Liquid Injection Incinerators
A liquid injection incinerator system consists of an incineration
chamber, waste burner and auxiliary fuel system. The combustion chamber
is a cylindrical steel shell lined with refractory material and mounted
horizontally or vertically. Liquid wastes are atomized as they are fed
into the combustion chamber through waste burner nozzles. Typical
combustion chamber temperatures are 1300-3000 deg.F and residence times
are from 0.5 to 3 seconds.
3. Fluidized Bed Incinerators
A fluidized bed system is essentially a vertical cylinder
containing a bed of granular material at the bottom. Combustion air is
introduced at the bottom of the cylinder and flows up through the bed
material, suspending the granular particles. Waste and auxiliary fuels
are injected into the bed, where they mix with combustion air and burn
at temperatures from 840-1500 deg.F. Further reaction occurs in the
volume above the bed at temperatures up to 1800 deg.F.
4. Fixed Hearth Incinerators
Fixed hearth incinerators typically contain two furnace chambers: a
primary and a secondary chamber. Some designs have two or three step
hearths on which ash and waste are pushed with rams through the system.
A controlled flow `underfire' combustion air is introduced up through
the hearths. The primary chamber operates in ``starved air'' mode and
the temperatures are around 1000 deg.F. The unburnt hydrocarbons reach
the secondary chamber where 140-200 percent excess air is supplied and
temperatures of 1400-2000 deg.F are achieved for more complete
combustion.
C. Number of Incinerator Facilities
Currently, 162 permitted or interim status incinerator facilities,
having 190 units, are in operation in the U.S. Another 26 facilities
are proposed 4 (i.e., new facilities under construction or
permitting). Of the above 162 facilities, 21 facilities are commercial
facilities that burn about 700,000 tons of hazardous waste annually.
The remaining 141 are on-site or captive facilities and burn about
800,000 tons of waste annually.
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\4\ USEPA ``List of hazardous waste incinerators,'' November
1994.
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D. Typical Emission Control Devices for Incinerators
Incinerators are equipped with a wide variety of air pollution
control devices (APCDs), which range from no control (for devices
burning low ash and low chlorine wastes) to sophisticated state-of-the-
art units providing control for several pollutants. Hot flue gases from
the incinerators are cooled and cleaned of the air pollutants before
they exit the stack. Cooling is mostly done by water quenching, wherein
atomized water is sprayed directly into the hot gases. The cooled gases
are passed through various pollution control devices to control PM,
metals and organic emissions to desired or required levels. Most
incinerators use wet APCDs to scrub acid emissions (3 facilities use
dry scrubbers). Typical APCDs used include packed towers, spray dryers,
or dry scrubbers for acid gas (e.g., HCl, Cl2) control, and
venturi-scrubbers, wet or dry electrostatic precipitators (ESPs) or
fabric filters for particulate control.
Activated carbon injection for controlling dioxin and mercury is
being used at only one incinerator. Newer APC technologies (such as
catalytic oxidizers and dioxin/furan inhibitors) have recently emerged,
but have not been used on any full scale facilities in the U.S. For
detailed description of APCDs, see Appendix A of ``Combustion Emissions
Technical Resource Document (CETRED),'' US EPA Document #EPA530-R-94-
014, May 1994.
II. Hazardous Waste-Burning Cement Kilns
A. Overview of Cement Manufacturing
Cement refers to the commodities that are produced by heating
mixtures of limestone and other minerals or additives at high
temperature in a rotary kiln, followed by cooling, grinding, and finish
mixing. This is the manner in which the vast majority of commercially-
important cementitious materials are produced in the United States.
Cements are used to chemically bind different materials together. The
most commonly produced cement type is ``Portland'' cement, though other
standard cement types are also produced on a limited basis (e.g.,
sulfate-resisting, high-early-strength, masonry, waterproofed).
Portland cement is a hydraulic cement, meaning that it sets and hardens
by chemical interaction with water. When combined with sand, gravel,
water, and other materials, Portland cement forms concrete, one of the
most widely used building and construction materials in the world.
Cement produced and sold in the U.S. must meet specifications
established by the American Society for Testing and Materials (ASTM).
Each type requires specific additives or changes in the proportions of
the raw material mix to make products for specific applications.
B. Summary of Major Design and Operating Features of Cement Kilns
Cement kilns are horizontally inclined rotating cylinders,
refractory-brick lined, and internally-fired, that calcine a blend of
raw materials
[[Page 17363]]
containing calcium (typically limestone), silica and alumina (typically
clay, shale, slate, and/or sand), and iron (typically steel mill scale
or iron ore) to produce Portland cement. Generally, there is a wet
process and a dry process for producing cement. In the wet process, the
limestone and shale are ground up, wetted and fed into the kiln as a
slurry. In the dry process, raw materials are ground dry and fed into
the kiln dry. Wet process kilns are typically longer than dry process
kilns in order to facilitate water evaporation from the slurried raw
material. Wet kilns can be more than 450 feet in length. Dry kilns are
more thermally efficient and frequently use preheaters or precalciners
to begin the calcining process (i.e., the essential function of driving
CO2 from raw materials) before the raw materials are fed into the
kiln.
Combustion gases and raw materials move in a counterflow direction,
with respect to each other, inside a cement kiln. The kiln is inclined,
and raw materials are fed into the upper end (i.e., the ``cold'' end)
while fuels are normally fired into the lower end (i.e., the ``hot''
end). Combustion gases move up the kiln counter to the flow of raw
materials. The raw materials get progressively hotter as they travel
down the length of the kiln. The raw materials eventually begin to
soften and fuse at temperatures between 2,250 and 2,700 deg.F to form
the clinker product. Clinker is then cooled, ground, and mixed with
other materials, such as gypsum, to form cement.
Combustion gases leaving the kiln typically contain from 6 to 30
percent of the free solids as dust, which are often recycled to the
kiln feed system, though the extent of recycling varies greatly among
cement kilns.
Dry kilns with a preheater (PH) or precalciner (PC) often use a by-
pass duct to remove from 5 to 30 percent of the kiln off-gases from the
main duct. The by-pass gas is passed through a separate air pollution
control system to remove particulate matter. Collected by-pass dust is
not reintroduced into the kiln system to avoid a build-up of metal
salts that can affect product quality.
Some cement kilns burn hazardous waste-derived fuels to replace
from 25 to 100 percent of normal fossil fuels (e.g., coal). Most kilns
burn liquid waste fuels but several also burn bulk solids and small
(e.g., six gallon) containers of viscous or solid hazardous waste
fuels. Containers are introduced either at the upper, raw material end
of the kiln or at the midpoint of the kiln. EPA has also found that
hazardous waste-fired precalciners can still be considered part of the
cement kiln and, thus, would be part of an industrial furnace (per the
definition in 40 CFR 260.10). See 56 FR at 7184-85 (February 21, 1991).
This finding is codified at Sec. 266.103(a)(5)(I)(c). This is the only
time (and the only rulemaking) in which the Agency found that a device
not enumerated in the list of industrial furnaces in Sec. 260.10 can be
considered part of the industrial furnace when it burns hazardous
wastes separate from those burned in the main combustion device.
C. Number of Facilities
The Agency has emissions data from 26 facilities representing 49
cement kilns in the U.S. It should be noted that some facilities no
longer burn or process hazardous waste since they were required to
certify compliance with the BIF regulations in August 1992.
Of the hazardous waste-burning kilns for which we have emissions
data, 14 facilities use a wet process, 5 facilities use a dry process,
and the remaining 7 facilities employ either preheaters or preheater/
precalciners in the cement manufacturing process.
D. Emissions Control Devices
All hazardous waste-burning cement kilns either use fabric filters
(baghouses) or electrostatic precipitators (ESPs) as air pollution
control devices. ESPs have traditionally been employed in the cement
industry and are currently used at 17 of the facilities. Nine
facilities use fabric filters. A detailed description of these and
other air pollution control devices is contained in the technical
support document. 5
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\5\ USEPA, ``Draft Technical Support Document for HWC MACT
Standards, Volume I: Description of Source Categories'', February
1996.
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III. Hazardous Waste-Burning Lightweight Aggregate Kilns
A. Overview of Lightweight Aggregate Kilns (LWAKs)
The term lightweight aggregate refers to a wide variety of raw
materials (such as clay, shale, or slate) which after thermal
processing can be combined with cement to form concrete products.
Lightweight aggregate concrete is produced either for structural
purposes or for thermal insulation purposes. A lightweight aggregate
plant is typically composed of a quarry, a raw material preparation
area, a kiln, a cooler, and a product storage area. The material is
taken from the quarry to the raw material preparation area and from
there is fed into the rotary kiln.
B. Major Design and Operating Features
A rotary kiln consists of a long steel cylinder, lined internally
with refractory bricks, which is capable of rotating about its axis and
is inclined at an angle of about 5 degrees to the horizontal. The
length of the kiln depends in part upon the composition of the raw
material to be processed but is usually 30 to 60 meters. The prepared
raw material is fed into the kiln at the higher end, while firing takes
place at the lower end. The dry raw material fed into the kiln is
initially preheated by hot combustion gases. Once the material is
preheated, it passes into a second furnace zone where it melts to a
semiplastic state and begins to generate gases which serve as the
bloating or expanding agent. In this zone, specific compounds begin to
decompose and form gases such as SO2, CO2, SO3, and
O2 that eventually trigger the desired bloating action within the
material. As temperatures reach their maximum (approximately
2100 deg.F), the semiplastic raw material becomes viscous and entraps
the expanding gases. This bloating action produces small, unconnected
gas cells, which remain in the material after it cools and solidifies.
The product exits the kiln and enters a section of the process where it
is cooled with cold air and then conveyed to the discharge.
Kiln operating parameters such as flame temperature, excess air,
feed size, material flow, and speed of rotation vary from plant to
plant and are determined by the characteristics of the raw material.
Maximum temperature in the rotary kiln varies from 2050 deg.F to 2300
deg.F, depending on the type of raw material being processed and its
moisture content. Exit temperatures may range from 300 deg.F to 1200
deg.F, again depending on the raw material and on the kiln's internal
design. Approximately 80 to 100 percent excess air is forced into the
kiln to aid in expanding the raw material.
C. Number of Facilities
EPA has identified 36 lightweight aggregate kiln locations in the
United States. Of these, EPA has identified seven facilities that are
currently burning hazardous waste in a total of 15 kilns.
D. Air Pollution Control Devices
Lightweight aggregate kilns use one or a combination of air
pollution control devices, including fabric filters, venturi scrubbers,
spray dryers, cyclones and wet scrubbers. All of the facilities utilize
fabric filters as the main type of emissions control, although one
facility uses a spray dryer, venturi scrubber and
[[Page 17364]]
wet scrubber in addition to a fabric filter. For detailed descriptions
of these and other air pollution control devices, please see Appendix A
of the draft EPA document Combustion Emissions Technical Resource
Document (CETRED). 6
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\6\ USEPA, ``Draft Combustion Emission Technical Resource
Document (CETRED)'', EPA 530-R-94-014, May 1994.
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PART THREE: DECISION PROCESS FOR SETTING NATIONAL EMISSION STANDARDS
FOR HAZARDOUS AIR POLLUTANTS (NESHAPs)
I. Source of Authority for NESHAP Development
The 1990 Amendments to the Clean Air Act significantly revised the
requirements for controlling emissions of hazardous air pollutants. EPA
is now required to develop a list 7 of categories of major and
area sources 8 of the hazardous air pollutants (HAPs) enumerated
in section 112 and to develop technology-based performance standards
for such sources over specified time periods. See Clean Air Act (the
Act or CAA) Secs. 112(c) and 112(d). Section 112 of the Act replaces
the previous system of pollutant-by-pollutant health-based regulation
that proved ineffective at controlling the high volumes,
concentrations, and threats to human health and the environment posed
by HAPs in air emissions. See generally S. Rep. No. 228, 101st Cong.
1st Sess. 128-32 (1990).
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\7\ The Agency published an initial list of categories of major
and area sources of HAPs on July 16, 1992. See 57 FR 31576.
\8\ See Part Three, Section III of today's proposal for a
discussion of major and area sources. Generally, a major source is a
stationary source that emits, or has the potential to emit
considering controls, 10 tons per year of a HAP or 25 tons per year
of a combination of HAPs. CAA Sec. 112(a)(1). An area source is
generally a stationary source that is not a major source. Id.
Sec. 112(a)(2).
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Section 112(f) also requires the Agency to report to Congress by
the end of 1996 on estimated risk remaining after imposition of
technology-based standards and to make recommendations as to
legislation to address such risk. CAA Sec. 112(f)(1). If Congress does
not act on the recommendation, then EPA must address any significant
remaining residual risks posed by sources subject to the section 112(d)
technology-based standards within 8 years after promulgation of these
standards. See Sec. 112(f)(2). The Agency is required to impose
additional controls if such controls are needed to protect public
health with an ample margin of safety, or to prevent adverse
environmental effects. Id. In addition, if the technology-based
standards for carcinogens do not reduce the lifetime excess cancer risk
for the most exposed individual to less than one in a million
(1 x 10-6), then the Agency must promulgate additional standards.
See Sec. 112(f)(2)(A).
II. Procedures and Criteria for Development of NESHAPs
NESHAPs are developed in order to control HAP emissions from both
new and existing sources according to the statutory directives set out
in Sec. 112. The statute requires a NESHAP to reflect the maximum
degree of reduction of HAP emissions that is achievable taking into
consideration the cost of achieving the emission reduction, any non-air
quality health and environmental impacts, and energy requirements.
Sec. 112(d)(2). In regulatory parlance, these are often referred to as
maximum achievable control technology (or MACT) standards.
The Clean Air Act establishes minimum levels, usually referred to
as MACT floors, for the emission standards. Section 112(d)(3) requires
that MACT floors be determined as follows: for existing sources in a
category or sub-category with 30 or more sources, the MACT floor cannot
be less stringent than the ``average emission limitation achieved by
the best performing 12 percent of the existing sources * * *''; for
existing sources in a category or sub-category with less than 30
sources, then the MACT floor cannot be less stringent than the
``average emission limitation achieved by the best performing 5 sources
* * *''; for new sources, the MACT floor cannot be ``less stringent
than the emission control that is achieved by the best controlled
similar source * * *''. See Sec. 112(d)(3) (A) and (B).
EPA must, of course, consider in all cases whether to develop
standards that are more stringent than the floor (``beyond the floor''
standards). To do so, however, EPA must consider the enumerated
statutory criteria such as cost, energy, and non-air environmental
implications.
Emission reductions may be accomplished through application of
measures, processes, methods, systems, or techniques, including, but
not limited to: (1) Reducing the volume of, or eliminating emissions
of, such pollutants through process changes, substitution of materials,
or other modifications; (2) enclosing systems or processes to eliminate
emissions; (3) collecting, capturing, or treating such pollutants when
released from a process, stack, storage, or fugitive emissions point;
(4) design, equipment, work practice, or operational standards
(including requirements for operator training or certification); or (5)
any combination of the above. See Sec. 112(d)(2).
Application of techniques (1) and (2) of the previous paragraph are
consistent with the definitions of pollution prevention under the
Pollution Prevention Act and the definition of waste minimization under
RCRA/HSWA. These terms have particular applicability in the discussion
of pollution prevention/waste minimization options presented in the
permitting and compliance sections of today's proposal.
To develop a NESHAP, the EPA compiles available information and in
some cases collects additional information about the industry,
including information on emission source quantities, types and
characteristics of HAPs, pollution control technologies, data from HAP
emissions tests (e.g., compliance tests, trial burn tests) at
controlled and uncontrolled facilities, and information on the costs
and other energy and environmental impacts of emission control
techniques. EPA uses this information in analyzing and developing
possible regulatory approaches. EPA, of course, does not always have or
collect the same amount of information per industry, but rather bases
the standard on information practically available.
Although NESHAPs are normally structured in terms of numerical
emission limits--the preferred means of establishing standards--
alternative approaches are sometimes necessary and appropriate. In some
cases, for example, physically measuring emissions from a source may be
impossible, or at least impractical, because of technological and
economic limitations. Section 112(h) authorizes the Administrator to
promulgate a design, equipment, work practice, or operational standard,
or a combination thereof, in those cases where it is not feasible to
prescribe or enforce an emissions standard.
EPA is required to develop emission standards based on performance
of maximum achievable control technology for categories or sub-
categories of major sources of hazardous air pollutants.
Sec. 112(d)(1). As explained more fully in the following section, a
major source emits, or has the potential to emit considering controls,
either 10 tons per year of any hazardous air pollutant or 25 tons or
more of any combination of those pollutants. Sec. 112(a)(1). EPA also
can establish lower thresholds where appropriate. Id. EPA
[[Page 17365]]
may in addition require sources emitting particularly dangerous
hazardous air pollutants (such as particular chlorinated dioxins and
furans) to be regulated under the MACT standards for major sources.
Sec. 112(c)(6).
Area sources are any source which is not a major source. Such
sources must be regulated by technology-based standards if they are
listed, pursuant to Sec. 112(c)(3), based on the Agency's finding that
these sources (individually or in the aggregate) present a threat of
adverse effects to human health or the environment warranting
regulation. After such a determination, the Agency has a further choice
as to require technology-based standards based on MACT or on generally
achievable control technology (GACT). Sec. 112(d)(5).
In this rulemaking, EPA is proceeding pursuant to Sec. 112(c)(6)
(i.e., imposing MACT controls on area sources), because these hazardous
waste combustion units emit a number of the HAPs singled out in that
provision, including the enumerated dioxins and furans, mercury, and
polycyclic organic matter. (See discussion below.)
III. List of Categories of Major and Area Sources
A. Clean Air Act Requirements
As just discussed, Section 112 of the CAA requires that the EPA
promulgate regulations requiring the control of hazardous air
pollutants emissions associated with categories or subcategories of
major and area sources. These source categories and subcategories are
to be listed pursuant to Sec. 112(c)(1). EPA published an initial list
of 174 categories of such major and area sources in the Federal
Register on July 16, 1992 (57 FR 31576).
B. Hazardous Waste Incinerators
``Hazardous waste incinerators'' is one of the 174 categories of
sources listed. The category consists of commercial and on-site
(including captive) incinerating facilities. The listing was based on
the Administrator's determination that at least one hazardous waste
incinerator may reasonably be anticipated to emit several of the 189
listed HAPs in quantities sufficient to designate them as major
sources. EPA used two emission rate values to evaluate the available
hazardous waste incinerator emissions data: the maximum emission rate
measured during the compliance test, and the average emission rate. The
data indicate that approximately 30 percent of the facilities meet the
major source criteria when using the maximum emissions rate value. When
using the average emissions rate value approximately 15 percent of
facilities meet the major source criteria.9 Those facilities
meeting the major source criteria do so for HCl and Cl2 emissions,
and one facility is also a major source for antimony emissions.
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\9\ For further details see USEPA, ``Draft Technical Support
Document for HWC MACT Standards, Volume I: Description of Source
Categories'', February 1996.
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It should be noted that a major source and boundary for considering
whether a source is a major includes all potential emission points of
HAPs at that contiguous facility, including storage tanks, equipment
leaks, and other hazardous waste handling facilities. The above
calculations for incinerators on whether a source is a major source
under Sec. 112 do not reflect these potential emission points.
Notwithstanding the fact that most HW incinerators are not likely
to meet the HAP emission thresholds for major sources, the Agency is
proposing to subject all HWCs to regulation under MACT as major
sources, under the authority of Sec. 112(c)(6). See Section IV below.
C. Cement Kilns
Another of the 174 categories of major and area sources of HAPs is
Portland Cement Manufacturing (cement kilns). In evaluating the
emissions data for the hazardous waste-burning cement kilns, 85 percent
of the cement kilns were determined to meet the major source criteria
when using the maximum emission rate value. Using the average emission
rate value, just over 80 percent of the hazardous waste-burning cement
kilns meet the major source criteria.10 Those facilities meeting
the major source criteria do so for HCl and Cl2 emissions, and one
facility is also a major source for organic emissions. It should be
noted that the calculation on whether a cement kiln is a major source
did not include potential emission points of HAPs at that contiguous
facility.
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\10\ Ibid.
---------------------------------------------------------------------------
Notwithstanding the fact that some hazardous waste-burning cement
kilns may not meet the definition of major source, the Agency is
proposing to subject all HWCs to regulation under MACT, as major
sources, under the authority of Sec. 112(c)(6). See Section IV below.
D. Lightweight Aggregate Kilns
Section 112(c)(5) authorizes EPA to amend the source category list
at any time to add categories or subcategories that meet the listing
criteria. EPA is proposing to exercise that authority by adding HW-
burning lightweight aggregate kilns to the list of source categories.
In analyzing the emissions data, EPA found that all hazardous
waste-burning LWAKs met the major source criteria for two HAPs, HCl and
Cl2, using either the average or maximum emission rate
value.11 It should be noted that the calculation on whether a LWAK
is a major source did not include potential emission points of HAPs at
that contiguous facility. EPA is therefore proposing today the addition
of hazardous waste-burning LWAKs as a source category in accordance
with section 112(c)(5) of the Act. In addition, as discussed below,
even if a LWAK would otherwise be an area source, EPA is proposing to
subject it to the same NESHAPS as major LWAK sources.
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\11\ Ibid.
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IV. Proposal To Subject Area Sources to the NESHAPs Under Authority of
Section 112(c)(6)
EPA is today proposing to subject all hazardous waste incinerators,
hazardous waste-burning cement kilns, and hazardous waste-burning
lightweight aggregate kilns (i.e., both area and major sources) to
regulation as major sources pursuant to CAA Sec. 112(c)(6). That
provision states that, by November 15, 2000, EPA must list and
promulgate Sec. 112 (d)(2) or (d)(4) standards (i.e., standards
reflecting MACT) for categories (and subcategories) of sources emitting
specific pollutants, including the following HAPs emitted by HWCs:
polycyclic organic matter, mercury, 2,3,7,8-tetrachlorodibenzofuran,
and 2,3,7,8-tetrachlorodibenzo-p-dioxin. (Although the Agency has not
prepared the list, it is the Agency's intention to include hazardous
waste combustors.) EPA must assure that sources accounting for not less
than 90 percent of the aggregate emissions of each enumerated pollutant
are subject to MACT standards.
The chief practical effect of invoking Sec. 112(c)(6) for this
rulemaking is to subject area sources that emit 112(c)(6) pollutants to
the same MACT standards as major sources, rather than to the
potentially less stringent 112(d)(5) or ``GACT'' (``generally
achievable control technology'') standards.12 Today's proposal
constitutes one of many EPA actions to assure that sources accounting
for at least 90 percent of
[[Page 17366]]
emissions of Sec. 112(c)(6) pollutants are subject to MACT standards.
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\12\ EPA also solicits comment on an alternative reading of
Sec. 112(c)(6), whereby the provision would require MACT control for
the enumerated pollutants but not necessarily for other HAPs emitted
by the source, which HAPs are not enumerated in Sec. 112(c)(6).
---------------------------------------------------------------------------
Although Sec. 112(c)(6) requires the Agency to regulate source
categories that emit not less than 90 percent of the aggregate
emissions of the high priority HAPs, the Agency will use its discretion
to avoid regulating area source categories with trivial aggregate
emissions of specific Sec. 112(c)(6) HAPs. However, as an example of
the emissions that are possible from the HWC source categories, it is
estimated that HWCs presently emit in aggregate 11.1 tons of mercury
per year. Of this quantity, 4.6 tons per year can be attributed to
hazardous waste incinerators and 6.5 tons per year to hazardous waste-
burning cement and lightweight aggregate kilns. Also, it is estimated
that HWCs presently emit in aggregate 122 pounds of dioxins/furans (or
2.15 pounds TEQ) per year. Of this quantity, 9 pounds (or 0.2 pounds
TEQ) per year can be attributed to hazardous waste incinerators and 113
pounds (or 1.95 pounds TEQ) per year to hazardous waste-burning cement
and lightweight aggregate kilns. To show an example of how today's
proposal constitutes an action to assure that sources accounting for at
least 90 percent of emissions of Sec. 112(c)(6) pollutants are subject
to MACT standards, the document Estimating Exposure to Dioxin-Like
Compounds, Vol. II: Properties, Sources, Occurrence and Background
Exposures (EPA, 1994) estimates (on p. 29) that national emissions of
dioxins and furans (D/F) total 4.18 pounds TEQ per year. Based on this
estimation, HWCs account for 51 percent of the annual national
emissions of D/F. (Consequently, EPA expects these source categories to
be included in the list of sources to be controlled to achieve the
requisite 90 percent reduction in aggregate emissions of section
112(c)(6) pollutants.)
Congress singled out the HAPs enumerated in Sec. 112(c)(6) as being
of ``specific concern'' not just because of their toxicity but because
of their propensity to cause substantial harm to human health and the
environment via indirect exposure pathways (i.e., from the air through
other media, such as water, soil, food uptake, etc.). S. Rep. No. 228,
101st Cong. 1st Sess., pp. 155, 166. These pollutants have exhibited
special potential to bioaccumulate, causing pervasive environmental
harm in biota (and, ultimately, human health risks). Id. Indeed, as
discussed later, the data appear to show that much of the human health
risk from emissions of these HAPs from HWCs comes from these indirect
exposure pathways. Id. at p. 166. Congress' express intention was to
assure that sources emitting significant quantities of Sec. 112(c)(6)
pollutants received a stricter level of control. Id.
V. Selection of MACT Floor for Existing Sources
The starting point in developing MACT standards is determining
floor levels, i.e. the minimum (least stringent) level at which the
standard can be set.
All of the hazardous waste combustion units subject to this
proposed rule are already subject to RCRA regulation under 40 CFR Parts
264, 265, or 266. As a result, the Agency has a substantial amount of
data reflecting performance of these devices. These data consist
largely of trial burn data for hazardous waste incinerators and data
from certifications of compliance for hazardous waste-burning cement
kilns and LWAKs obtained pursuant to 266.103(c). These data consist of
at least three runs for any given test condition.
In using these ``short term'' test data to establish a MACT floor,
the Agency has developed an approach that ensures the standards are
achievable, i.e. reflect the performance over time of properly designed
and operated air pollution control devices (or operating practices)
taking into account intrinsic operating variability.
In addition, the Agency notes that the floor calculations were
performed on individual HAPs or, in the case of metals, in two groups
of HAPs that behave similarly (i.e., separate floor levels for each
hazardous air pollutant or group of metal pollutants). However, for
HAPs that are controlled by the same type of air pollution control
device (APCD), EPA has ensured that all HAP floors are simultaneously
achievable by identifying the APCD and APCD treatment train that can be
used to meet all floor levels. The ultimate floor levels thus derived
can be achieved using the identified technology. This approach is
consistent with methods used by EPA in other rules to calculate MACT
requirements where the HAP species present must be treated by a
treatment train. See, e.g., MACT Rules for Secondary Lead Smelters. 60
FR 32589 (June 23, 1995).
The Agency is not, however, treating hazardous waste-burning
incinerators, cement kilns, and LWAKs as a single source category for
purposes of developing the MACT floor (or for any other purpose). The
Agency's initial view is that there are technical differences in
performance for particular HAPs among the three source categories, and
therefore that the technology-based floors must reflect these operating
differences.
A. Proposed Approach: Combined Technology-Statistical Approach
This analysis first identified the best performing control
technology(ies) for each source category (i.e., incinerators, cement
kilns, and lightweight aggregate kilns) and each HAP of concern by
arraying from lowest to highest all the particular HAP emissions data
from existing units within the source category by test condition
averages. These technologies comprise MACT floor. In cases where a
source had emissions data for a HAP from several different test
conditions of a compliance test, the Agency arrayed each test condition
separately. The Agency then identified the emission control technology
or technologies (and normalized feedrate of metals and chlorine in
hazardous waste) used by sources with emissions levels at or below the
level emitted by the median of the best performing 12 percent of
sources. The sources are termed ``the best performing 6 percent'' of
the sources, or ``MACT pool'', and the controls they use comprise MACT
floor.
The next step was to identify an emissions level that MACT floor
control could achieve. Thus, emissions data from all sources (in the
source category) that use MACT floor control were arrayed in ascending
order by average emissions. [This is referred to as the ``expanded MACT
pool'' or ``expanded universe''.] The Agency evaluated the control
technologies used by the additional sources within the ``expanded
universe'' as available data allowed to ensure that they were in fact
equivalent in design to MACT floor. The Agency then selected the test
condition in the expanded MACT pool with the highest mean emissions to
identify the emission level that MACT floor could achieve.
Because the emissions database was comprised of ``short-term'' test
data, the Agency used a statistical approach to identify an emission
level that MACT floor could achieve routinely. The Agency then
identified the test condition in the expanded MACT pool with the
highest mean emissions to statistically calculate a ``design level''
and a floor standard. The design level was calculated as the log mean
of the emissions for the test condition. The standard was calculated as
a level that a source (that is designed and operated to routinely meet
the design level) could meet 99 percent of the time if it has the
average within-test-condition emissions variability of the expanded
MACT pool. Although the Agency evaluated 90th and 95th percentile
limits, the 99th
[[Page 17367]]
percentile limit was chosen to: (1) More accurately reflect the
variability that could be present in emissions data, and (2)
appropriately characterize this variability in light of the consequence
of failing to achieve the emissions standards. Additional information
on how MACT floor levels were identified is provided in the ``Draft
Technical Support Document for HWC MACT Standards, Volume III:
Selection of Proposed MACT Standards and Technologies''.
In accounting for operating variability, the Agency solicits
comment on whether it may have overcompensated so that the identified
floor levels are unduly lenient. The test data on which the proposal is
based to some extent reflect worst-case performance conditions because
RCRA sources try to obtain maximum operating flexibility by conducting
test burns at extreme operating conditions. For example, many sources
spike wastes with excess metals and chlorine during compliance testing.
In addition, sources operate their emissions control devices under low
efficiency conditions (while still meeting emission standards) to
ensure lenient operating limits. It thus may be that the Agency's
emissions database is so inflated that separate consideration of
emissions variability may not be warranted. A floor level could be the
highest mean of the test conditions in the expanded MACT pool.
The Agency emphasizes that it would be preferable, for purposes of
setting these MACT standards, to have operational and emissions data
that better reflect long-term, more routine day-to-day facility
operations from all of the source categories. We believe that this type
of data would enable the MACT process to articulate a set of HAP
standards that would not create some of the issues raised in subsequent
sections of this preamble (such as the most appropriate resolution of a
variability factor, the optimum approach for considering the
contribution of cement and lightweight aggregate kiln raw material feed
to HAP emissions, and better identification among sources that are now
in an expanded MACT pool but which, with better data, would be
determined not to be employing the identified floor controls). As noted
in these subsequent sections, the Agency urges commenters to submit
these types of data.
B. Another Approach Considered but not Used
Although the Agency believes the proposed approach reflects a
reasonable interpretation of the statute, there are other possible
interpretations. One of these interpretations, termed the ``12 percent
approach'', was raised and, in fact, evaluated during the process
already outlined. This approach is presented here, along with the
results of the process in Part Four, Section VIII, for public
inspection.
This ``12 percent approach'' was evaluated in a like manner to the
Agency's preferred approach just described. Again, the best performing
control technology(ies) for each source category and each HAP were
identified by arraying the data by test condition averages. However,
the Agency identified the technology or technologies used by the best
performing 12 percent of the sources. After arraying emissions data
from all facilities in the source category that use the identified MACT
floor technology(ies) (i.e., the expanded MACT pool), the Agency
selected an emissions floor level based on the statistical average of
the 12 percent MACT pool, to which was added the average within-test
condition variability within the expanded MACT pool. The emissions
floor was then calculated at a level that a source with average
emissions variability would be expected to achieve 99 percent of the
time. The approach was not proposed because it could not be
demonstrated that sources within the expanded MACT pool using MACT
floor controls could achieve the floor levels. Again, the details of
the statistical methods employed are presented in the ``Draft Technical
Support Document for HWC MACT Standards, Volume III: Selection of
Proposed MACT Standards and Technologies''.
C. Identifying Floors as Proposed in CETRED
The discussion in the Draft Combustion Emissions Technical Resource
Document (CETRED) (U.S. EPA, EPA530-R-94-014, May 1994) presented one
methodology for establishing particulate matter (PM) and dioxin/furan
(D/F) technology-based emission levels for hazardous waste combustors
(HWCs). The document presented a procedure for establishing numerical
levels which took into account the natural variability that was present
in the Agency's PM and D/F emissions data. EPA received numerous
comments on the document.
The approaches outlined in CETRED were an initial and preliminary
attempt to apply the process by which the NESHAPs are to be established
for the existing types of hazardous waste combustors. The approaches in
CETRED focused solely on the performance of MACT and how to establish
the ``floor'' emission level under the MACT process.
In CETRED, determination of the MACT floor involved: (1) screening
unrepresentative data; (2) ranking all HWC sources based on the data
average, considering variability; (3) identifying the top 12 percent of
sources as the MACT pool; and (4) statistically evaluating the MACT
pool to set the MACT floor. These elements and considerations are
described in further detail in CETRED and the ``Draft Technical Support
Document for HWC MACT Standards, Volume III: Selection of Proposed MACT
Standards and Technologies''. The Agency specifically indicated the
preliminary nature of the CETRED approaches and, in light of further
deliberations and comments received, has considered and adopted other
approaches for this proposal. The comments received are found in the
docket.
In considering the use of a purely statistical approach to setting
MACT floors, the Agency recognized that whether sources could actually
achieve a statistically-derived MACT floor level on a regular basis was
significant in determining whether a purely statistical approach could
be appropriate or not. The Agency encountered difficulties in
identifying an appropriate purely statistical model for the combined
source category (HW incinerators, HW-burning cement kilns, and HW-
burning lightweight aggregate kilns) emissions database. Consequently,
the Agency abandoned a purely statistical approach and examined an
approach--referred to here as the ``technology approach''--that used
demonstrated technological capabilities as a key factor in selecting
MACT floor levels.
D. Establishing Floors One HAP or HAP Group at a Time
EPA believes it is permissible to establish MACT floors separately
for individual HAPs or group of HAPs that behave the same from a
technical standpoint (i.e., based on separate MACT pools and floor
controls), provided the various MACT floors are simultaneously
achievable. As set out below, Congress has not spoken to this precise
issue. An interpretation that allows this approach is consistent with
statutory goals and policies, as well as established EPA practice in
developing MACT standards.
As described earlier, Congress specified in section 112(d)(3) the
minimum level of emission reduction that could satisfy the requirement
to adopt MACT. For new sources, this floor level is to be ``the
emission control that is achieved in practice by the best
[[Page 17368]]
controlled similar source''. For existing sources, the floor level is
to be ``the average emission limitation achieved by the best performing
12 percent of the existing sources'' for categories and subcategories
with 30 or more sources, or ``the average emission limitation achieved
by the best performing 5 sources'' for categories and subcategories
with fewer than 30 sources. An ``emission limitation'' is ``a
requirement * * * which limits the quantity, rate, or concentration of
emissions of air pollutants'' (section 302 (k)) (although the extent,
if any, the section 302 definitions need to apply to the terms used in
section 112 is not clear).
This language does not expressly address whether floor levels can
be established HAP-by-HAP. The existing source MACT floor achieved by
the average of the best performing 12 percent can reasonably be read as
referring to the source as a whole or performance as to a particular
HAP. The statutory definition of ``emission limitation'' (assuming it
applies) likewise is ambiguous, since ``requirements limiting quantity,
rate, or concentration of pollutants'' could apply to particular HAPs
or all HAPs. The reference in the new source MACT floor to ``emission
control achieved by the best controlled similar source'' can mean
emission control as to a particular HAP or achieved by a source as a
whole.
Here, Congress has not spoken to the precise question at issue, and
the Agency's interpretation effectuates statutory goals and policies in
a reasonable manner. See Chevron v. NRDC, 467 U.S. 837 (1984)
(indicating that such interpretations must be upheld). The central
purpose of the amended air toxics provisions was to apply strict
technology-based emission controls on HAPs. See, e.g., H. Rep. No. 952,
101st Cong. 2d sess. 338. The floor's specific purpose was to assure
that consideration of economic and other impacts not be used to ``gut
the standards''. While costs are by no means irrelevant, they should by
no means be the determining factors. There needs to be a minimum degree
of control in relation to the control technologies that have already
been attained by the best existing sources. Legislative History of the
Clean Air Act Vol. II at 2897 (statement of Rep. Collins).
Furthermore, an alternative interpretation would tend to result in
least common denominator floors where multiple HAPs are emitted,
whereby floors would no longer be reflecting performance of the best
performing sources. For example, if the best performing 12 percent of
facilities for HAP metals did not control organics as well as a
different 12 percent of facilities, the floor for organics and metals
would end up not reflecting best performance. Indeed, under this
reading, the floor would be no control, because no plant is controlling
both types of HAPs.
EPA is convinced that this result is not compelled by the statutory
text, and does not effectuate the evident statutory purpose of having
floor levels reflect performance of an average of a group of best-
performing sources. Conversely, using a HAP-by-HAP approach (or an
approach that groups HAPs based on technical factors) to identify
separate floors for metals and organics in this example promotes the
stated purpose of the floor to provide a minimum level of control
reflecting what best performing existing sources have already
demonstrated an ability to do.
EPA notes, however, that if optimized performance for different
HAPs is not technologically possible due to mutually inconsistent
control technologies (for example, metals performance decreases if
organics reduction is optimized), then this would have to be taken into
account in establishing a floor (or floors). (Optimized controls for
both types of HAPS would not be MACT in any case, since the standards
would not be mutually achievable.) The Senate Report indicates that in
such a circumstance, EPA is to optimize the part of the standard
providing the most environmental protection. S. Rep. No. 228, 101st
Cong. 1st sess. 168. It should be emphasized, however, that ``the fact
that no plant has been shown to be able to meet all of the limitations
does not demonstrate that all the limitations are not achievable''.
Chemical Manufacturers Association v. EPA, 885 F. 2d at 264 (upholding
technology-based standards based on best performance for each pollutant
by different plants, where at least one plant met each of the
limitations but no single plant met all of them).
All available data for HWCs indicate that there is no technical
problem achieving the floor levels for each HAP or HAP metal group
simultaneously, using the MACT floor technology. In the case of metals
and PM, the characteristics of the MACT floor technology associated
with the hardest-to-meet floor (e.g., the fabric filter with lowest
air-to-cloth ratio) would define the MACT floor technology for purposes
of determining achievability of floors and for purposes of costing out
the impact of the standards. Existing data show that approximately 9
percent of existing hazardous waste incinerators, approximately 8
percent of hazardous waste-burning cement kilns, and approximately 25
percent of hazardous waste-burning LWAKs are already achieving the
proposed floor standards for all HAPs.
Finally, EPA notes that the HAP-by-HAP or HAP group approach to
establishing MACT floor levels is not unique to this rule. For example,
the Agency has adopted it for the NESHAP for the secondary lead source
category (60 FR 32589 (June 23, 1995)) and proposed the same approach
for municipal waste combustors (59 FR 48198 (September 20, 1994)).
As discussed above, EPA has the authority to establish MACT floors
on a HAP group by HAP group basis and has done so in this case. In
doing so, EPA will ensure that such floors, taken as a whole, are
reasonably achievable for facilities subject to the MACT standards.
VI. Selection of Beyond-the-Floor Levels for Existing Sources
As discussed in Section V above, the MACT floor defines the minimum
level of emission control for existing sources, regardless of cost or
other considerations. The process of considering emissions levels more
stringent than the MACT floor for existing sources is called a
``beyond-the-floor'' (BTF) analysis and involves consideration of
certain additional factors, including cost, any non-air quality health
and environmental impacts and energy requirements, technologies
currently in use within these industry sectors, and also other more
efficient and appropriate technologies that have been demonstrated and
are available on the market (e.g., carbon bed for dioxin/furan
control).
Because there are virtually unlimited BTF emissions levels that the
Agency could consider, the Agency used several criteria in this
proposal to identify when to examine a particular beyond-the-floor
emissions level in detail, and also whether to propose a MACT standard
based on the beyond-the-floor emissions levels for existing sources.
The primary factor is the cost-effectiveness of setting MACT
standards based upon a more efficient technology than the MACT floor
technology(ies). If the Agency's economic analysis suggested that BTF
levels could be cost-effectively achieved (particularly if significant
health benefits would result from a lower emission level), then an
applicable BTF emission level control technology was identified to
achieve that level. The associated costs were then weighed along with
the other criteria. Dioxin/furans is an example
[[Page 17369]]
where the Agency considered a BTF level because a beyond-the-floor
emission level can be achieved in a cost-effective manner, achieving,
in addition, significant non-air quality environmental benefits.
VII. Selection of MACT for New Sources
For new sources, the standards for a source category (or sub-
category) cannot be less stringent than the emission control that is
achieved in practice by the best-controlled similar source. See
Sec. 112(d)(3). The following discussion summarizes the methodology
used by the Agency in developing today's proposed emissions standards
for new HWC sources.
The approach used to identify MACT for new sources parallels in
most ways the approach used to determine the MACT floor for existing
sources. For each HAP, the Agency identified the technology associated
with the single best performing source (for each source category). The
Agency used this best performing technology then looked at all
facilities operating the control technology, and determined the
achievable emission levels that represent ``the emission control that
is achieved in practice by the best controlled similar source'' by
using the maximum value achieved by properly-operated technology
(adjusted upwards by a statistically derived variability factor). For
further details, see the technical background documents \13\ supporting
today's proposal.
---------------------------------------------------------------------------
\13\ USEPA, ``Draft Technical Support Document for HWC MACT
Standards, Volume III: Selection of Proposed MACT Standards and
Technologies'', February 1996.
---------------------------------------------------------------------------
Since MACT for new sources is to reflect optimized achievable
performance and is not necessarily limited to performance levels
currently achieved, the Agency also considered several other factors in
selecting the MACT new emissions limit. These factors included: (1)
Comparisons to other emissions standards which may indicate that a
technology is demonstrated and its level of performance (e.g., proposed
municipal waste combustors and medical waste incinerators regulations
and the European Union waste incineration standards); and (2) test
condition emissions variability.
As mentioned earlier, the Agency believes that it is appropriate to
compare the proposed emissions standards for new sources to other
existing or recently proposed standards applicable to hazardous waste
combustors or similar devices as a type of ``reality check'' that we
are developing the most rigorous emissions limits for new sources based
upon the best technologies available today.
The extracted data and data plots are presented in the background
document \14\ located in the docket.
---------------------------------------------------------------------------
\14\ USEPA, ``Draft Technical Support Document for HWC MACT
Standards, Volume III: Selection of Proposed MACT Standards and
Technologies'', February 1996.
---------------------------------------------------------------------------
VIII. RCRA Decision Process
It is EPA's intention to eliminate duplicative or potentially
duplicative regulation wherever possible. In this section, we discuss:
(1) The RCRA mandate to ensure protection of human health and the
environment and how that mandate relates to the CAA technology-based
MACT standards; (2) how, for RCRA purposes, we evaluated the
protectiveness of the proposed MACT standards; (3) how, for RCRA
purposes, the Agency intends to continue its policies with respect to
site-specific risk assessments and permitting so that, in appropriate
situations, additional RCRA permit conditions can be developed as
necessary to protect human health and the environment; and (4) how
waste minimization opportunities may be considered at individual
facilities during the permitting process.
A. RCRA and CAA Mandates To Protect Human Health and the Environment
The Agency is proposing emission standards for HWCs under joint
authority of the Clean Air Act Amendments of 1990 and the Resource
Conservation and Recovery Act (RCRA). As noted earlier, section 3004(a)
of RCRA requires the Agency to promulgate standards for hazardous waste
treatment, storage, and disposal facilities as necessary to protect
human health and the environment. The standards for incinerators
generally rest on this authority. In addition, Sec. 3004(q) requires
the Agency to promulgate standards as necessary to protect human health
and the environment specifically for facilities that burn hazardous
waste fuels (e.g., cement and light-weight aggregate kilns). Using RCRA
authority, the Agency has historically established emission (and other)
standards for HWCs that are either entirely risk-based (e.g., site-
specific standards for metals under the BIF rule), or are technology-
based but determined by a generic risk assessment to be protective
(e.g., the DRE standard for incinerators and BIFs).
The MACT standards proposed today implement the technology-based
regime of CAA Sec. 112. There is, however, a residual risk component to
air toxics standards. Section 112(f) of the Clean Air Act requires the
Agency to impose, within eight years after promulgation of the
technology-based standards promulgated under Sec. 112(d) (i.e., the
authority for today's proposed standards), additional controls if
needed to protect public health with an ample margin of safety or to
prevent adverse environmental effect. (Cost, energy, and other relevant
factors must be considered in determining whether regulation is
appropriate in the case of environmental effects.)
As noted earlier, EPA's express intent is to avoid regulatory
duplication. RCRA Sec. 1006 directs that EPA ``integrate all provisions
of [RCRA] for purposes of administration and enforcement and * * *
avoid duplication, to the maximum extent possible, with the appropriate
provisions of the Clean Air Act * * *.'' The overall thrust of the
proposed rule is to have the CAA standards supplant independent RCRA
standards wherever possible (i.e., to have the CAA standards, wherever
possible, also serve to satisfy the RCRA mandate so that additional
RCRA regulation is unnecessary).
Under RCRA, EPA must promulgate standards ``as may be necessary to
protect human health and the environment.'' RCRA Sec. 3004(a) and (q).
Technology-based standards developed under CAA Sec. 112 do not
automatically satisfy this requirement, but may do so in fact. See 59
FR at 29776 (June 6, 1994) and 60 FR at 32593 (June 23, 1995) (RCRA
regulation of secondary lead smelter emissions unnecessary at this time
given stringency of technology-based standard and pendency of
Sec. 112(f) determination). If the MACT standards, as a factual matter,
are sufficiently protective to also satisfy the RCRA mandate, then no
independent RCRA standards are required. Conversely, if MACT standards
are inadequate, the RCRA authorities would have to be used to fill the
gap.
It should be noted that this RCRA risk evaluation can inform the
MACT decision process as well. For example, the RCRA risk evaluations
indicate the potential for significant risk via indirect pathways from
dioxins and furans originating in today's baseline air emissions for
HWCs. EPA is explicitly authorized to consider non-air environmental
impacts (such as exposure to HAPS which, after emission, enter into the
food chain and are eventually consumed by humans and other biota) in
determining whether to adopt standards more stringent than the MACT
floor. Thus, EPA can consider benefits from curbing these
[[Page 17370]]
indirect exposures as part of its beyond-the-floor determinations.
As discussed below, the Agency has conducted an evaluation, for the
purposes of satisfying the RCRA statutory mandates, of the degree of
protection afforded by the MACT standards being proposed today.
However, the Agency's current RCRA evaluation is not intended to have
any bearing on what we may or may not determine is necessary in several
years to satisfy the Sec. 112(f) provisions.
B. Evaluation of Protectiveness
To determine whether the MACT standards are consistent with the
Agency's mandate under RCRA to establish standards for hazardous waste
management facilities and to issue permits that are protective of human
health and the environment, the Agency conducted two types of analyses
to assess the extent to which potential risks from current hazardous
waste combustion emissions would be reduced through implementation of
MACT standards.
The first of these analyses was designed to assess the potential
risks to individuals living near hazardous waste combustion facilities
and to nearby aquatic ecosystems. The procedures used in this analysis
are discussed in detail in the background document contained in the
docket for today's proposal.15 The results are summarized in Part
Four of today's notice, ``Rationale for Selecting Proposed Standards''.
---------------------------------------------------------------------------
\15\ ``Risk Assessment Support to the Development of Technical
Standards for Emissions from Combustion Units Burning Hazardous
Wastes: Background Information Document,'' February 20, 1996.
---------------------------------------------------------------------------
The second analysis of potential risk reduction was a more
qualitative evaluation of risks at the national level for those two
constituents (dioxins and mercury) which the Agency believes pose
significant health risks at the national level and which are found at
significant concentrations in hazardous waste combustor emissions. The
results of this analysis are presented in Section Seven, ``Regulatory
and Administrative Requirements'', as part of the discussion of
potential costs and benefits required under Executive Order 12866.
1. Individual Risk Analysis
The Agency assessed potential risks to individuals from both direct
inhalation of emissions (after dispersion in the ambient air) and
indirect exposure to emissions through deposition onto soils and
vegetation and subsequent uptake through the food chain. The analysis
focussed primarily on dioxins and related compounds since these have
been of major concern to the Agency from a risk perspective and because
there is enough information about the properties of these constituents
to allow for a quantitative analysis. The individual risk analysis did
also include risks from inhalation of metals, hydrogen chloride, and
chlorine (Cl2).
The Agency conducted an evaluation of risks from metals through
indirect exposure routes. With the exception of mercury, most of the
metals are not expected to accumulate significantly in the food chain,
and the risks from other indirect exposure routes (such as deposition
on soil and incidental ingestion of the soil) are not projected to be
significant, even with conservative assumptions.
With respect to mercury, the Agency suspects that there may be
significant individual risks near hazardous waste combustion
facilities, primarily through deposition, erosion to surface waters,
and accumulation in fish which are then consumed. However, the current
state of knowledge concerning the behavior of mercury in the
environment does not allow for a meaningful quantitative risk
assessment of emission sources which is precise enough to support
regulatory decisions at the national level. Specifically, there is
insufficient information with respect to speciation of the mercury into
various forms in emissions and with respect to the deposition and
cycling of mercury species in the environment to conduct a defensible
national quantitative assessment of mercury deposition, erosion to
surface waters, and bioaccumulation in fish. The Agency solicits
comment and information on the issue of the risks posed by mercury
emissions from hazardous waste combustion facilities.
The Agency also considered potential risks from emissions of non-
dioxin semi-volatile organics that are products of incomplete
combustion (PICs). However, the Agency was not able to conduct an
appropriate analysis for several reasons. First, the limited emissions
data now available to the Agency on non-dioxin PICs are not
sufficiently reliable to conduct an adequate assessment of risk.
Second, there is not a universally accepted set of parameter values for
some non-dioxin PICs with which to assess potential exposures (e.g.,
the use of octanol-water partition coefficients (Kow) to predict
bioaccumulation versus the use of empirical data and the extent to
which bioaccumulation of compounds such as phthalates and polycyclic
aromatic hydrocarbons (PAHs) occurs in domestic animals). The Agency
solicits comment on these issues and, in particular, requests data on
bioaccumulation of PAHs, phthalates, and other non-dioxin PICs in farm
animals used for food production and in other mammals and birds. The
Agency also intends to obtain a better set of data relating to the non-
dioxin PIC emissions from hazardous waste combustion facilities.
2. Individual Risks From Dioxins
In order to evaluate potential risks from dioxins to individuals
living near hazardous waste combustion facilities, the Agency selected
eleven example facility locations, consisting of areas in which five
actual cement kilns, four incinerators, and two lightweight aggregate
kilns are located. The example facility locations represent a variety
of environmental settings and facility characteristics. The purpose of
using example facilities was to incorporate as much realism as possible
into the Agency's risk assessment and to reduce the reliance on
hypothetical, conservative assumptions about either location or source
type characteristics. Site-specific characteristics considered in the
analysis include meteorological conditions, topography, and land use as
well as stack height and gas flow rates. However, the stack gas
concentrations used in the modeling of the example facilities were
derived from national emissions data. Therefore, while the example
facility analyses are useful for providing information to evaluate
national standards on a generic basis, they are not site-specific
assessments of any individual facility and cannot be regarded as such.
The Agency has identified a number of indirect exposure pathways
which are most likely to present significant risks. These include:
consumption of locally-produced meat, eggs, and dairy products and
consumption of fish from local waterways. Contamination of food occurs
from deposition of toxic emissions onto plants and soil with subsequent
ingestion by farm animals or, in the case of fish contamination, from
deposition directly into water bodies or onto soil and runoff into
surface waters with subsequent uptake in fish.
In assessing risks to the more highly exposed individuals, the
Agency assumed that certain segments of the population subsisted in
part on home-produced foods or fish obtained from nearby lakes or
streams. In addition, the Agency assumed that these individuals were
exposed in the farming and fishing areas most affected by the example
facilities' emissions. In its analysis of the eleven example
facilities, the
[[Page 17371]]
Agency attempted to identify the actual location of farms and water
bodies where subsistence activities might be expected to occur. For
dioxins, the highest exposures are expected to occur for individuals
whose diets include significant amounts of home-produced meat and eggs
or locally caught fish. Individuals likely to have high exposures
include subsistence farmers that raise beef cattle, dairy cows, or
chickens along with their families as well as subsistence fishers and
recreational anglers and their families.
In evaluating individual risks, the Agency projected both ``high
end'' and ``central tendency'' estimates of risks to the individuals of
concern in the analysis. The central tendency estimates were derived by
setting all emission rates, fate and transport parameters, and exposure
assumptions at central tendency values, as described in the risk
assessment background document. To derive high end risk estimates, the
Agency set the emission levels at the 90th percentile of the
distribution of available dioxin concentrations and, for most exposure
scenarios, set one exposure parameter to a high end value while keeping
all other parameters at central tendency values. For purposes of
evaluating the protectiveness of the standards, the Agency used a
target risk level of 10-5 for the high end individual risk, which is
consistent with the approach taken in the 1991 BIF rule.
3. Uncertainties in the Individual Dioxin Risk Estimates
Much of the information used to derive the individual risk
estimates for dioxins was taken from the Agency's draft Dioxin
Reassessment documents \16\ \17\ \18\. Those documents discuss in
considerable detail a number of the uncertainties associated with both
the cancer slope factor (the dose-response descriptor) and the many
parameters used in the exposure assessment. Some of these uncertainties
are also discussed in the risk assessment background document for
today's proposal.
---------------------------------------------------------------------------
\16\ ``Health Assessment Document for 2,3,7,8-
Tetrachlorodibenzo-p-Dioxin (TCDD) and Related Compounds Volume I
and II'', Office of Research and Development, June 1994.
\17\ ``Health Assessment Document for 2,3,7,8-
Tetrachlorodibenzo-p-Dioxin (TCDD) and Related Compounds Volume
III'', Office of Research and Development, August 1994.
\18\ ``Estimating Exposure to Dioxin-Like Compounds Volume I,
II, and III'', Office of Research and Development, June 1994.
---------------------------------------------------------------------------
In addition, there have been a large number of public comments on
the Dioxin Reassessment, which the Agency is now considering. If the
Agency decides to revise its assessment of either the toxicity or
exposure associated with dioxins prior to the final promulgation of
this rule, those revisions will be considered in the development of the
final rule.
The Agency is also conducting an external peer review of its risk
analysis supporting today's proposal. The results of this peer review,
which are expected during the comment period, will be available in the
public record for this rule and will be considered in developing the
final rule.
4. Qualitative Assessments of National Risks
While the individual risk assessment discussed above provides a
quantitative measure of the protectiveness of the proposed MACT
standard, there are other ways of evaluating potential impacts of
reducing emissions of hazardous constituents. One approach taken by the
Agency is to describe to the extent practicable what is known about the
national extent of risks from constituents such as dioxins and mercury.
To put that information in context with respect to this rule, the
relative contribution of hazardous waste combustion to other known air
releases of these constituents to the environment is then presented.
The Agency recognizes that it is not appropriate to quantitatively
correlate emissions with risk on a national scale; nevertheless, this
type of information is useful for qualitatively evaluating the
potential impact of the proposed MACT rule.
C. Use of Site-Specific Risk Assessments Under RCRA
As part of the Agency's Hazardous Waste Minimization and Combustion
Strategy, EPA currently has a national RCRA policy of strongly
recommending to all federal and state RCRA permit writers that, under
the omnibus permit provisions of RCRA Sec. 3005(c)(3), site-specific
risk assessments be performed as part of the RCRA permitting process if
necessary to protect human health and the environment. Regions and
authorized states have been implementing this national policy since
mid-1993 under the aegis of the omnibus and other applicable
authorities.
The Combustion Strategy announced this policy encouraging site-
specific risk assessments as part of the overall effort to ensure that,
under appropriate legal authorities, all RCRA combustion permits being
issued are sufficiently protective. Specifically, these site-specific
risk assessments were intended to address potential concerns about a
suite of hazardous air pollutants, among them dioxins, furans, metals,
and non-dioxin PICs, during the time it took for the Agency to upgrade
the technical standards for hazardous waste incinerators, boilers, and
industrial furnaces. This proposal is the first rulemaking that the
Agency has issued in the upgrading effort.
The question has arisen as to the status of the Agency's current
policy with respect to site-specific risk assessments, particularly
with respect to the HAPs for which standards are being proposed today
as well as for other non-dioxin PICs. As noted above, the Agency has
conducted a risk evaluation under RCRA of the degree of protection
afforded by the proposed MACT standards for the HAPs addressed in
today's rule. However, with respect to mercury and non-dioxin PICs, the
Agency does not at this time have sufficient reliable data to be able
to assess, on a national basis, the magnitude of the risks that can
routinely be expected from burning hazardous waste in HWCs. Although
the Agency has plans to obtain extensive and detailed PIC emissions
data from hazardous waste combustors in the coming months, it may be
some time before the Agency is in a proper position to make any type of
regulatory and policy judgment about the need, if any, for additional
national standards for these toxic organics. Indeed, at several sites,
the levels of some non-dioxin PICs have not previously been shown to be
of concern, at least to the extent that site-specific testing revealed
their presence and to the extent evaluated in site-specific risk
assessments.
The Agency is continuing its policy of recommending that, if
necessary to protect human health and the environment, site-specific
risk assessments be conducted as part of RCRA permitting for all
hazardous waste combustors (incinerators, boilers, and industrial
furnaces alike) until national standards for HAPs of concern are in
place. We expect that, in most situations prior to actual
implementation of facility measures to appropriately control the HAPs
addressed in this rule, the EPA regional and authorized state
permitting officials will find there is a necessity to conduct site-
specific risk assessments prior to final permit determinations. We also
note that the remaining uncertainties about the risks from non-dioxin
PICs and mercury would likely bear upon implementation of the national
policy. However, small on-site facilities are not likely to present the
same level of potential risk as other facilities. This industry segment
may not warrant site specific risk assessments with the same frequency
as the large on-site or
[[Page 17372]]
commercial facilities. Among the factors that the regions and states
should consider in their evaluation of the necessity for a site-
specific risk assessment are: (1) The current level of HAPs being
emitted by a facility, particularly in comparison to the MACT standards
being proposed and in comparison to the emissions assumptions and
exposure scenarios used in the RCRA risk evaluation of the proposed
MACT standards (detailed in the Background Document); (2) whether the
facility is exceeding the proposed HAP standards, particularly for
dioxins/furans and mercury, what immediate measures could be instituted
to reduce those emissions; (3) the scope of waste minimization efforts
at the facility with respect to the HAPs of concern and the status of
implementation of any facility waste minimization plan; (4) particular
site-specific considerations such as proximity to receptors, unique
dispersion patterns, etc.; (5) the PICs most likely to be found and
those most likely to pose significant risk; (6) the presence or absence
of other sources of HAPs in sufficient proximity as to exert a
significant influence on interpretation of a facility-specific risk
assessment; (7) the presence or absence of significant ecological
considerations, including for example high background levels of a
particular contaminant or proximity of a particularly sensitive
ecological area; and (8) the volume and types of wastes being burned.
This list is by no means exhaustive, but is meant only to suggest
significant factors that have thus far been identified. Others may be
equally or more important.
Continuation of the site-specific risk assessment policy rests
primarily on the RCRA requirement to ensure that all permits are
protective of human health and the environment. Until the Agency is in
a position to determine, on a national basis, whether additional
standards are needed to address toxic emissions, we anticipate this
policy will remain in effect. EPA's intention is to make that
determination, if sufficient data is in hand, by the time of the final
rule, now scheduled for issuance in December 1996. In that respect, we
emphasize the importance of the submission of detailed data on non-
dioxin PICs from commenters.
In the meantime, the omnibus provision in Sec. 3005(c)(3) provides
the regions and authorized states with the proper site-by-site
authority to ensure that these risk assessments are completed as part
of the permitting process. Other RCRA statutory and regulatory
provisions may apply as well. Furthermore, we encourage individual
facilities to work with their local communities in designing these risk
assessments and in carrying out the testing and analysis, so that the
confidence of local communities is maximized.
In addition, EPA strongly urges companies to explore waste
minimization opportunities as a means to reduce risks from combustion
emissions, particularly with respect to the HAPs of concern. Nearly
every state provides free pollution prevention/waste minimization
technical assistance. Further information on how to obtain this
assistance can be furnished by state permitting agencies or by
contacting the National Pollution Prevention Roundtable at (202) 466-
7272. Other sources of information include Enviro$ense, an electronic
library on pollution prevention, technical assistance, and
environmental compliance. Access is via a system operator (703) 908-
2007, via modem at (703) 908-2092, or via Internet at http://
wastenot.inel.gov/enviro-sense.
PART FOUR: RATIONALE FOR SELECTING THE PROPOSED STANDARDS
This part describes the Agency's rationale for today's proposed
standards and other options under consideration.
I. Selection of Source Categories and Pollutants
A. Selection of Sources and Source Categories
The Agency is proposing emissions standards for three source
categories: hazardous waste incinerators, hazardous waste-burning
cement kilns, and hazardous waste-burning lightweight aggregate kilns.
The Agency is not proposing to regulate emissions from CKs (in this
notice) or LWAKs that do not burn hazardous waste.
In this section, we discuss the Agency's analysis of subdividing
incinerators by size (i.e., small and large sources) and subdividing
cement kilns by process type (i.e., wet and dry). We also discuss the
scope of the MACT standards for cement kilns, and the existing RCRA
standards that control emissions of HAPs from equipment leaks and tanks
which are used to manage hazardous waste.
1. Consideration of Subdividing Incinerators by Size
Section 112(d) allows the Administrator to distinguish among
classes, types, and sizes of sources within a source category in
establishing MACT floor levels. Given that the size of incinerators, as
measured by gas flow rate in actual cubic feet per minute (acfm),
varies substantially (i.e., from 1,000 acfm to 180,000 acfm), the
Agency considered subdividing incinerators by size.
The basis for distinguishing between small and large incinerators
as well as the preliminary estimates of the resultant floor levels for
each category are presented in the docket and summarized below. The
Agency is not proposing separate standards (at the floor) 19 for
incinerators because: (1) the types and concentrations of uncontrolled
HAP emissions are similar for large and small incinerators; (2) the
same types of emission control devices are applicable to both small and
large incinerators; and (3) the floor levels would be generally
unchanged 20 (several floor levels would decrease somewhat), with
the exception that the LVM standard for large incinerators would
increase by more than a factor of four. We believe that the higher LVM
floor level for large incinerators would not be appropriate given that
approximately 80 percent of incinerators already are meeting the LVM
floor without subdividing.
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\19\ Note that we discuss in Part Four, Section III in the text
whether beyond-the-floor standards for D/F, Hg, and PM (as currently
proposed for all incinerators) are appropriate for small
incinerators.
\20\ And therefore, a level of complexity would be added to the
rule without substantial benefit.
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The Agency invites comment on its determination that subdividing
incinerators by size would not be warranted. We also invite comment on
whether subdividing incinerators by other classifications (e.g.,
commercial versus on-site units) would be appropriate for establishing
MACT floor levels. Commenters should provide data and information on,
in particular: (1) how the types and concentrations of uncontrolled HAP
emissions are different for the suggested categorization of sources;
(2) whether and why MACT emission control technology would not be
applicable to a category of sources; and (3) other appropriate factors.
To investigate the effect on MACT floor levels of subdividing
incinerators by size, the Agency identified a gas flow rate of 23,127
acfm as a reasonable and appropriate demarcation between small and
large incinerators. This value was determined using a slope analysis
approach whereby gas flow rates for each source (for which the Agency
had data) were plotted in ascending order. The Agency chose the point
at which the slope markedly changed as the point of demarcation between
small and large incinerators. Approximately 57 percent of incinerators
for which we have gas flow rate data would be classified as small using
this approach.
[[Page 17373]]
Projected MACT floor levels for small and large incinerators are
compared to floor levels for combined incinerators (i.e., without
subdividing) in the table below:
------------------------------------------------------------------------------------------------------------------------------------------------
Small incinerators Large incinerators
------------------------------------------------------------------------ Floor levels for all incinerators
Floor level Floor level combined
------------------------------------------------------------------------------------------------------------------------------------------------
D/F (ng/dscm)....................... 0.2 TEQ or <400 deg.F............... 0.2 TEQ or <400 deg.F............... 0.2 TEQ or <400 deg.F.
PM (mg/dscm)........................ 180.................................. 180.................................. 180
Hg (g/dscm)................ 110.................................. 130.................................. 130
SVM (g/dscm)............... 230.................................. 270.................................. 270
LVM (g/dscm)............... 160.................................. 880.................................. 210
HCl + Cl2 (ppmv).................... 280.................................. 260.................................. 280
CO (ppmv)........................... 100.................................. 100.................................. 100
HC (ppmv)........................... 12................................... 12................................... 12
-----------------------------------------------------------------------------------------------------------------------------------------------
2. Consideration of Subdividing Cement Kilns by Manufacturing Process
The Agency also considered whether to subdivide the cement kiln
source category into wet and dry process kilns given that these types
of kilns are designed and operated differently. (See discussion in Part
Two, Section II.) MACT floor levels for wet and dry kilns are compared
in the table below:
-----------------------------------------------------------------------------------------------------------------------------------------------
Wet process kilns Dry process kilns
Pollutant ----------------------------------------------------------------------- Floor levels for all kilns combined
Floor level Floor level
------------------------------------------------------------------------------------------------------------------------------------------------
D/F (ng/dscm)....................... 0.2 TEQ or 418 deg.F................ 0.2 TEQ or 547 deg.F................ 0.2 TEQ or 418 deg.F.
PM (mg/dscm)........................ 69................................... 69................................... 69
Hg (g/dscm)................ 83................................... 150.................................. 130
SVM (g/dscm)............... 870.................................. 57................................... 57
LVM (g/dscm)............... 220.................................. 49................................... 130
HCl + Cl2 (ppmv).................... 460.................................. 340.................................. 640
------------------------------------------------------------------------------------------------------------------------------------------------
Subdividing cement kilns by process type would result in a mix of
impacts with varying degrees of significance. For wet kilns, the main
impact would be an increase in the SVM floor from 57 to 870 g/
dscm. The mercury floor, on the other hand, would drop from 130 to 83
g/dscm. The remainder of the floors would remain roughly the
same. For dry cement kilns, the main impact would be that the LVM floor
drops from 130 to 49 g/dscm. The dioxin/furan floor would
change by allowing a higher APCD temperature--547 deg.F rather than
418 deg.F.
The Agency is not proposing separate standards for wet and dry
process kilns because: (1) The types and concentrations of uncontrolled
HAP emissions are similar for both types of kilns; (2) the same types
of emission control devices are applicable to both types of kilns; (3)
for dry process kilns, the LVM floor level would drop to an extremely
low level that may be difficult for many kilns to achieve because of
the presence of these metals in raw materials; and (4) for wet kilns,
the SVM floor would increase to 870 g/dscm, a level much
higher than the industry can achieve.21 There may also be other
factors that should be considered, and the Agency invites comment on
those in addition to the factors noted above.
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\21\ See letter from Craig Campbell, CKRC, to James Berlow,
USEPA, undated but received February 20, 1996. We note that,
although the Agency is proposing a SVM standard of 57 g/
dscm, we invite comment on an alternative (and potentially
preferable) approach to identify MACT floor technology which would
result in a floor-based standard of 160 g/dscm. See Part
Four, Section IV in the text. Because we identified the alternative
approach late in the rule development process, we are inviting
comment on the higher standard rather than proposing it.
---------------------------------------------------------------------------
We note that the cement industry has asserted that it is not
feasible to use a FF on wet kilns in cold climates because the ``high
moisture content of the gas will clog the fabric with cement-like dust
and ice.'' 22 This is not consistent with the Agency's
understanding. Although wet kilns located in cold climates that operate
at low flue gas temperatures (e.g., 350-400 deg.F) in order to
minimize formation of D/F and improve performance of activated carbon
injection systems may be required to improve insulation or take other
measures to minimize cold spots in the baghouse to limit corrosion, we
believe that appropriate measures can be readily taken. The Agency is
aware of two wet kilns that currently operate fabric filters in cold
climates (Thomaston, Maine, and Dundee, Michigan) at flue gas
temperatures below 400 deg.F. \23\ In addition, a wet kiln
burning hazardous waste in Paulding, Ohio, is currently upgrading its
PM control system to replace an ESP with a FF.
---------------------------------------------------------------------------
\22\ See letter from Micheal O'Bannon, EOP Group, to Elliot
Laws, USEPA, dated February 14, 1996, p. 3 of Attachment.
\23\ See USEPA, ``Draft Technical Support Document For HWC MACT
Standards, Volume III: Selection of Proposed MACT Standards and
Technologies'', February, 1996, for further information.
---------------------------------------------------------------------------
The Agency invites comment on the appropriate criteria to be used
and upon its determination that subdividing cement kilns by process
type is not warranted. Commenters should provide data and information
on, in particular: (1) Whether the types and concentrations of
uncontrolled HAP emissions are different for wet and dry kilns; (2)
whether and why MACT emission control technology(ies) would not be
applicable to a wet or dry kiln; and (3) other appropriate factors.
3. Scope of the MACT Standards for Cement Kilns
The proposed NESHAP for cement kilns addresses only exhaust
combustion gas emissions from main stack(s), bypass stack(s), and
fugitive combustion emissions (e.g., leaks from kiln seals). The cement
kiln standards would not apply to process or fugitive emissions that
are not affected
[[Page 17374]]
by burning hazardous waste (such as emissions from raw material
processing or clinker cooler emissions). 24
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\24\ Today's proposal applies only to those kilns that burn or
process hazardous waste irrespective of the purpose of burning or
processing. The term ``burn'' means burning for energy recovery or
destruction, or processing as an ingredient. The Agency is
developing a NESHAP for cement kilns that do not process hazardous
waste in a separate rulemaking. That NESHAP will also regulate those
hazardous waste-burning cement kiln process and fugitive emissions
that would not be subject to today's rule (i.e., emission sources
other than the main or by-pass stack).
---------------------------------------------------------------------------
4. Current RCRA Controls on Equipment Leaks and Tanks
We note that the Agency has promulgated air emission standards
regulating fugitive emissions from equipment leaks (e.g., pumps,
compressors, valves) and tanks which are used to manage hazardous
waste. Accordingly, these devices are not addressed by today's
proposal. (Tanks and equipment leaks from HW management activities at
HWCs are regulated under RCRA standards. See, e.g., 40 CFR Parts 264
and 265, Subparts AA, BB, and CC. These controls are expected to be
consistent with MACT and are not being reevaluated here.)
B. Selection of Pollutants
As noted earlier, section 112(b) of the Clean Air Act contains a
list of 189 hazardous air pollutants for which the Administrator must
promulgate regulations establishing emissions standards for designated
major and area sources. The list of 189 HAPs is comprised of metallic,
organic, and inorganic compounds.
Hazardous waste incinerators and hazardous waste-burning cement
kilns and LWAKs emit many of the listed HAPs. Data available to the
Agency indicate that metal HAP emissions include antimony, arsenic,
beryllium, cadmium, chromium, lead, mercury, nickel, and selenium
compounds. Organic HAPs emitted include chlorinated dioxin and furan,
benzene, carbon disulfide, chloroform, chloromethane,
hexachlorobenzene, methylene chloride, naphthalene, phenol, toluene,
and xylene. Hydrochloric acid and chlorine gas are prevalent inorganic
compounds found in stack emissions because of high chlorine content of
many hazardous wastes.
Today, the Agency is proposing eight emissions standards for
individual HAPs, group of HAPs, or HAP surrogates. These emission
standards cover dioxin/furan, mercury, particulate matter, semivolatile
HAP metals (lead and cadmium), low-volatile HAP metals (antimony,
arsenic, beryllium, and chromium), carbon monoxide, hydrocarbons, and
total chlorides. The following discussion presents the Agency's
rationale for proposing NESHAPs for these individual HAPs, group of
HAPs, or HAP surrogates.
1. Toxic Metals
In developing today's proposed rule, the Agency considered 14 toxic
metals that may pose a hazard to human health and the environment when
they are components of emissions from hazardous waste combustion
sources. Section 112(b) of the Act contains a list of 11 metal HAPs:
antimony, arsenic, beryllium, cadmium, chromium, cobalt, lead,
manganese, mercury, nickel, and selenium. The list of hazardous
constituents under RCRA 25 specifies three additional metals:
barium, silver, and thallium. Five of these metals (or their compounds)
are known or suspected carcinogens: arsenic, beryllium, cadmium,
hexavalent chromium, and nickel.
---------------------------------------------------------------------------
\25\ The list of hazardous constituents is contained in appendix
VIII of Part 261. Cobalt and manganese are not hazardous
constituents.
---------------------------------------------------------------------------
To develop an implementable approach for controlling the metal HAP
emission levels, the Agency grouped metal HAPs by their relative
volatility and is proposing an emissions limit for the each volatility
group (i.e., the sum of emissions from the metals in the group cannot
exceed the limit). We selected the following three groups: (1) A high-
volatile group comprised of only mercury, (2) a semivolatile group
comprised of lead and cadmium, and (3) a low-volatile group consisting
of antimony, arsenic, beryllium, and chromium. The Agency's proposal
not to include the remaining seven toxic metals in these volatility
groupings is discussed later in this section.
Our data indicate that mercury is generally in the vapor form in
and downstream of the combustion chamber, including at the air
pollution control device (APCD). Thus, the level of emissions is a
function of the feedrate of mercury and the use of APCDs that can
control Hg in the vapor form (e.g., carbon injection, wet scrubbers for
some control of soluble HgCl). The semivolatile group metals typically
vaporize at combustion temperatures, then condense onto fine
particulate before entering the APCD. Thus, emissions of semivolatile
metals are a function not only of the feedrate of the metal, but also
of the efficiency of the particulate matter (PM) control device. Low-
volatile metals are less apt to vaporize at combustion temperatures and
therefore partition primarily to the bottom ash, residue, or clinker
(in the case of cement kilns) or adsorb onto large, easy-to-control
particles in the combustion gas. Thus, low-volatile metal emissions are
more strongly related to the operation of the PM APCD than to the
feedrate.26
---------------------------------------------------------------------------
\26\ Although, at a given PM emission rate at a source,
emissions of LMV will be affected by LVM feedrate.
---------------------------------------------------------------------------
We note that the dynamics associated with the fate of metals in a
combustion device are much more complex than presented here. Numerous
factors impact metals' behavior such as the presence of chlorine
(higher metal volatility associated with metal chlorides than metal
oxides), combustion conditions within the device (e.g., temperature
profile), inter-metal relationships, physical and chemical form the
metal exhibits when introduced to the device (e.g., valence state and
solid versus liquid), type and efficiency of the particulate control
device, and differences in the design and operation of sources (e.g.,
cement kiln dust recycling rate). See the technical background document
supporting today's proposal for more details.27
---------------------------------------------------------------------------
\27\ USEPA, ``Draft Technical Support Document for HWC MACT
Standards, Volume VII: Miscellaneous Technical Issues'', February
1996.
---------------------------------------------------------------------------
Setting an emission level for a number of grouped metals has
several advantages and disadvantages. One advantage is that fewer
individual standards are involved, which helps implementability.
Moreover, grouping allows a facility more flexibility in complying with
an emissions standard based on facility-specific characteristics (e.g.,
special characteristic waste streams) and operation requirements (e.g.,
reduced spiking of numerous metals). On the other hand, a disadvantage
of a group emission limit is that it potentially allows higher
emissions of the more toxic metals within a group (than if an
individual metal limit were established).28
---------------------------------------------------------------------------
\28\ We note that, for the risk assessment used to determine if
RCRA concerns would be adequately addressed by the proposed MACT
standards, we assumed that each metal in a volatility was emitted in
turn at the emission limit for that volatility group.
---------------------------------------------------------------------------
The Agency is proposing not to regulate directly emissions of the
remaining four metal HAPs (i.e., cobalt, manganese, nickel, and
selenium).29 The
[[Page 17375]]
Agency's rationale is based upon a combination of factors: (1)
Inadequate emissions data for Co, Mg, Ni, and Se; and (2) relatively
low toxicity of Co and Mn. The Agency specifically requests comment on
whether these four metals would be adequately controlled under the MACT
standards that would be provided by today's proposal.
---------------------------------------------------------------------------
\29\ The Agency acknowledges that three metals (barium, silver
and thallium), currently regulated by the BIF rule, would not be
regulated under this MACT proposal. EPA notes that these three
metals are not HAPs. The Agency believes that the combination of the
proposed particulate and metals standards would adequately control
emissions of these three metals.
---------------------------------------------------------------------------
The Agency is aware of two other approaches to group toxic metals.
First, the European Union has established three groupings to control
metal emissions from hazardous waste incineration units. One ``group''
includes only mercury, a second group consists of cadmium and thallium,
and the third group includes antimony, arsenic, chromium, cobalt,
copper, lead, manganese, nickel, tin, and vanadium. Section VII of this
Part summarizes the European Union emission standards.
A rulemaking petition 30 submitted to the Agency by the Cement
Kiln Recycling Coalition (CKRC) contained a report 31 (appendix D
of the petition) prepared by a technical advisory board to the CKRC.
Their analysis of stack emissions and cement kiln dust data suggests
three volatility groupings based on metal volatility demonstrated in
cement kilns. The groupings are: (1) Volatile metals including mercury
and thallium; (2) semivolatile metals consisting of antimony, cadmium,
lead, and selenium; and (3) low-volatile metals comprising barium,
beryllium, chromium, arsenic, nickel, manganese, and silver. See the
technical background document for further discussion on grouping metals
by volatility.32 The Agency requests comments on the
appropriateness of grouping metals by volatility and requests
supporting information and data on the appropriate composition of metal
volatility groups (i.e., for the metals discussed above).
---------------------------------------------------------------------------
\30\ CKRC's rulemaking petition proposes to establish new
technology-based combustion emissions standards and was submitted to
EPA on January 18, 1994. CKRC's petition consists of four basic
components. First, the stringency of current BIF Rule toxic metal
limits should be increased by factors of 5 to 10 and applied to all
combustion devices (i.e., both BIFs and incinerators). Second, new
regulatory efforts for dioxin/furan standards should focus on a
toxic equivalency approach (TEQ) rather than on a total congener
approach. Third, the implementation of the new metals and dioxin/
furan standards should be applied uniformly to all types of
hazardous waste combustors (HWCs) and imposed at the same time.
Finally, EPA should conduct a rulemaking on indirect exposure risk
assessments before requiring their use. CKRC's petition has been
placed in the docket supporting today's proposal.
\31\ ``Scientific Advisory Board on Cement Kiln Recycling
(Process Technology Workgroup), Evaluation of the Origin, Emissions
and Control of Organic and Metal Compounds From Cement Kilns Co-
Fired With Hazardous Wastes,'' June 8, 1993.
\32\ USEPA, ``Draft Technical Support Document for HWC MACT
Standards, Volume VII: Miscellaneous Technical Issues,'' February
1996.
---------------------------------------------------------------------------
2. Toxic Organic Compounds
Burning hazardous waste that contains toxic organic compounds under
poor combustion conditions can result in substantial emissions of HAPs
originally present in the waste as well as other compounds, due to the
partial but incomplete combustion of the constituents in the waste
(known as products of incomplete combustion, or PICs). PICs can be
unburned organic compounds that were present in the waste, thermal
decomposition products resulting from organic constituents in the
waste, or compounds synthesized during or immediately after combustion.
The quantity of toxic organic compounds emitted depends on such factors
as the combustion conditions under which the waste is burned (including
time, temperature, and turbulence), the concentrations of the toxic
compounds in the waste, and the waste firing rate.
Since the majority of the 189 enumerated HAPs are organics, the
Agency has concluded (for today's proposal) that establishing
individual emission limits for each of the organic HAP compounds
emitted from these combustion sources would be impractical and not
implementable. Measuring each compound would be very costly and would
pose unreasonable compliance and monitoring burden on the regulated
community while achieving little, if any, emission reduction from the
approach presented in today's proposal. In addition, EPA and state
compliance oversight and enforcement efforts would also be unreasonably
costly without concurrent benefits. Also, the Agency does not have
adequate emissions data to support development of individual organic
emission limits 33 at this time. Therefore, the Agency is
proposing a multi-faceted approach to control the toxic organic HAPs to
be addressed under Sec. 112: (1) Emissions limits for dioxin and furan
on a toxicity equivalents (TEQ) basis; (2) limits on flue gas
concentrations of hydrocarbons (HC) as a HAP surrogate; (3) limits on
flue gas concentrations of carbon monoxide (CO) also as a HAP
surrogate; and (4) emission limits for particulate matter (PM) to
control adsorbed semivolatile organic HAPs (see separate discussion on
PM below).
---------------------------------------------------------------------------
\33\ The number of organic HAPs measured at each facility varies
widely with some facilities reporting measurements for a large
number of HAPs while other facilities measuring only a few HAPs.
---------------------------------------------------------------------------
First, given the high toxicity of some dioxin and furan congeners
and the fact that standards ensuring good operating conditions alone
(i.e., temperature at the inlet of the APCD) will not always control
emissions of dioxin/furans
(D/F), the Agency has determined that proposing an emission standard
specifically for D/F is a necessary component to the multi-faceted
approach for toxic organics emissions control. The D/F standard
proposed today is based on TEQ (Toxicity Equivalents).34 TEQ is a
method for assessing the risks associated with exposures to complex
mixtures of chlorinated dibenzo-p-dioxin and dibenzofurans (CDDs and
CDFs). The method relates the toxicity of the 209 structurally related
chemical pollutants to the toxicity of 2,3,7,8-tetrachlorodibenzo-p-
dioxin (2,3,7,8-TCDD).
---------------------------------------------------------------------------
\34\ The TEQ approach used for today's proposal is the I-TEQ/89
approach defined in USEPA, ``Interim Procedure for Estimating Risks
Associated With Exposures to Mixtures of Chlorinated Dibenzo-p-
Dioxin and -Dibenzofurans (CDDs and CDFs) and 1989 Update,'' March
1989. For a discussion of establishing D/F limits based on TEQ
versus total congeners, see USEPA, ``Combustion Emissions Technical
Resource Document (CETRED),'' May 1994, pp. 4-21.
---------------------------------------------------------------------------
Second, the Agency is proposing to use carbon monoxide (CO) and
hydrocarbons (HC) as surrogates to control emissions of non-D/F organic
HAPs. We note that limiting CO and HC emissions to levels ensuring good
combustion conditions would also help minimize D/F precursors. CO and
HC emissions are both recognized indicators of combustion intensity and
completeness. Low CO flue gas levels are indicative of a combustion
device operating at high combustion efficiency (56 FR at 7149-54).
Operating at high combustion efficiency helps ensure minimum emissions
of unburned (or incompletely burned) organics. However, limiting CO may
not by itself absolutely minimize PIC emissions. This is because PICs
can result from small pockets within the combustion zone where adequate
time, temperature, turbulence, and oxygen have not been provided to
completely oxidize these organics.35 As combustion becomes less
efficient or less complete, at some point, the emissions of total
organics (measured as HC) will increase. A
[[Page 17376]]
portion of the HC emission is comprised of organic HAPs. Thus, CO
levels provide an indication of the potential for organic HAP emissions
and CO limits are therefore proposed as a measure to help prevent these
emissions. HC limits are proposed to document actual emissions of
organic HAPs.36
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\35\ We note that there are emissions data indicating that even
though CO levels are below 100 ppmv, HC emissions can exceed 5 ppmv
(measured as propane with a heated sampling system), the upper HC
level that is generally representative of operating under good
combustion conditions. See 56 FR 7154, note 26 (February 21, 1991),
and Energy and Environmental Research Corporation, ``Surrogate
Evaluation of Thermal Treatment Systems,'' Draft Report dated
October 17, 1994, Figure 2-1.
\36\ We note that virtually all HWCs are already equipped with a
CO monitor because of RCRA requirements. In addition, several
incinerators, cement kilns and lightweight aggregate kilns are also
equipped with a HC monitor because of RCRA or state requirements or
voluntary initiative.
---------------------------------------------------------------------------
Notwithstanding today's proposal to establish MACT standards for
both CO and HC emissions for HWIs and LWAKs (CKs would be required to
comply with either a CO or HC standard for technical reasons discussed
in Section IV below), the Agency invites comment on whether standards
for both CO and HC (coupled with the D/F and PM standards to also
control organic HAPs) are unnecessarily redundant. Commenters should
provide data and information on how either CO or HC alone (but in
conjunction with
D/F and PM standards) would ensure proper control of organic HAPs. In
particular, commenters should address the fact that the Agency's
database indicates that HC levels can exceed good combustion condition
levels when CO levels are below 100 ppmv (thus suggesting that controls
on both CO and HC are needed). In addition, commenters should address
how the MACT standards proposed today for HC would or could ensure that
sources operate under good combustion conditions and thus minimize
emissions of organic HAPs.
If based on review of comments and further analysis the Agency
determines that standards for both CO and HC are not warranted, we
would consider, among other potential options, the following
alternative regulatory approaches: (1) Give each source the option of
complying with either the CO or HC standard (as proposed today for
technical reasons for by-pass duct gas for cement kilns); or (2)
establish a national standard for either CO or HC, but not both (the
Agency would determine which parameter is more appropriate and
establish a standard for that parameter). The Agency invites comment on
these alternative regulatory approaches or others that would ensure
proper control of organic HAP emissions.
3. Hydrochloric Acid (HCl) and Chlorine (Cl2)
Both hydrochloric acid and chlorine are designated HAPs that are
present in HWC emissions. However, the test method used to determine
HCl and Cl2 emissions (BIF methods 0050, 0051, and 9057, commonly
referred to as ``Method 26A'') 37 may not be able to distinguish
between HCl and Cl2 in all situations.38 Therefore, EPA
proposes combining the two HAPs into a single HCl and Cl2
standard. We believe this is appropriate because emissions of both of
these HAPs can be controlled by limiting feedrate of chlorine in
hazardous waste and wet scrubbing.39
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\37\ We note that owners and operators of cement kilns have
argued that this method provides measurements that are biased high
because metallic salts penetrate the filter and the chloride is
incorrectly reported as HCl. EPA has considered this concern and
continues to believe that metallic salts do not significantly bias
the results. Nonetheless, we invite comment on this issue. If, in
fact, metallic salts can bias the results, we invite comment
particularly on how or whether the proposed MACT standards could be
adjusted given the inflated emissions database, and how compliance
with an adjusted standard could be demonstrated.
\38\ In the presence of other halogens (e.g., fluorine and
bromine) that are often constituents of hazardous waste, fossil
fuels or kiln raw materials, EPA is concerned that reactions can
occur in the impinger solutions used by the stack sampling method
that cause a portion of the Cl2 to be reported as HCl. Thus,
the HCl levels could be biased high, and the Cl2 levels could
be biased low. Nonetheless, the method does continue to give an
accurate determination of combined HCl and Cl2 levels in the
presence of other halogens.
\39\ We also note that, for purposes of determining whether the
proposed MACT standard would satisfy RCRA concerns, we evaluated the
level of protection that would be provided assuming (conservatively)
that 10 percent of the HCl/Cl2 standard would be emitted as the
more toxic Cl2.
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4. Particulate Matter (PM)
EPA is proposing to use particulate matter (PM) as a surrogate for
non-D/F organic HAPs (that are adsorbed onto the PM) and for the metal
HAPs which are not specified in the metals standards (i.e., Co, Mn, Ni,
and Se).40 More than 40 semivolatile organic HAPs can be adsorbed
onto PM and can, thus, be controlled by a MACT standard for PM.41
The metal HAPs that are not directly controlled by the MACT standards
for metals can also be controlled (at least partially) by a PM
standard. The low volatility metals are likely to be entrained in
larger particulates and the semivolatile metals are likely to be
condensed onto small particulates.
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\40\ We note that PM 10 is a criteria pollutant under the Clean
Air Act. PM can also have adverse effects on human health even if
toxics are not adsorbed on the PM. Although EPA cannot control PM in
and by itself under Sec. 112(d) (it must be a surrogate for HAP
control), EPA may consider reductions in criteria pollutants in
assessing cost-effectiveness of MACT controls. See S. Rep. No. 228,
101st Congress, 1st Session, p. 172.
\41\ See memo from Larry Gonzalez, EPA, to the docket for this
rule (F-96-RCSP-FFFFF), entitled ``Semi-volatile Organic HAPs that
Can Be Adsorbed onto PM'', dated February 22, 1996.
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The Agency notes that we are proposing to use PM also as a
compliance parameter to ensure compliance with the SVM, LVM, and D/F
standards. As discussed in Part V, Section II, of the preamble, a site-
specific PM operating limit would be established as a surrogate for the
PM control device collection efficiency. Given that we are also
proposing a PM MACT emission standard, the site-specific operating
limit for PM could not exceed the PM standard.
C. Applicability of the Standards Under Special Circumstances
In this section, we discuss the applicability of the proposed MACT
standards under the following circumstances: (1) When a regulated metal
or chlorine is not present in the hazardous waste at detectable levels;
(2) when the source temporarily ceases hazardous waste burning; and (3)
when the source terminates hazardous waste burning.
1. Nondetect Levels of Metals or Chlorine in All Feedstreams
If no feedstreams to a HWC (e.g., on-site incinerator) contain
detectable levels of Hg, SVM, LVM, or chlorine, the source would not be
subject to the emission standard associated with the metal or chlorine
(e.g., if no feedstreams contain detectable levels of chlorine, the
HCl/Cl2 standard would be waived). In addition, performance
testing, monitoring, notification, and recordkeeping requirements
ancillary to the waived standard would also be waived. We believe that
this waiver is appropriate because the source would be incompliance
with the emission standard by default if it was not feeding the metal
or chlorine.
To be eligible for the waiver, the source must develop and
implement a feedstream sampling and analysis plan to document that no
feedstream contains detectable levels of the metal or chlorine (for
which a waiver is claimed).
The Agency invites comment on whether it is necessary to specify
minimum detection levels (or to take other measures) to ensure that
appropriate analytical procedures are used to document levels of metal
or chlorine in feedstreams.
2. Nondetect Levels of Metals or Chlorine in the Hazardous Waste Feed
The proposed MACT standards for mercury, SVM, LVM, or chlorine
would apply even if these constituents are not present at detectable
levels in the
[[Page 17377]]
hazardous waste. This issue is relevant for cement kilns and light-
weight kilns because, if these sources were not burning hazardous
waste, the proposed MACT standards would not apply. Cement kilns (CKs)
that do not burn hazardous waste would be subject to separate MACT
standards that the Agency is developing for those sources, and light-
weight aggregate kilns (LWAKs) that do not burn hazardous waste would
not be subject to any MACT standards.
It could be argued that a CK or LWAK that burns hazardous waste
with nondetect levels of Hg, SVM, LVM, or chlorine is not burning
hazardous waste with respect to that metal or the HCl/Cl2
standard. Accordingly, regulation should revert to any applicable MACT
standard for the source when not burning hazardous waste. The Agency
rejects this argument, however. A source cannot be subject to
regulation under two MACT source categories. Further, such an approach
would be extremely difficult to implement and enforce for CKs given
that compliance procedures would be different for the two source
categories.
3. Sources That Temporarily Cease Burning Hazardous Waste
Sources that temporarily cease burning hazardous waste would remain
subject to today's proposed standards. Similar to the discussion above,
such sources could argue that in the interim when hazardous waste is
not burned, MACT regulation should revert to the MACT standards
applicable to CKs or LWAKs that do not burn hazardous waste.
The Agency rejects this argument as well and for the same reasons
discussed above: a source cannot be intermittently subject to MACT
regulation under two source categories, and implementation and
enforcement would be extremely complicated. See the discussion below
regarding how to define temporary interruptions in waste burning versus
termination of waste burning.
4. Sources That Terminate Hazardous Waste Burning
A source that terminates hazardous waste burning would no longer be
subject to today's proposed rules. A source has terminated hazardous
waste burning when it: (1) ceases burning hazardous waste (i.e.,
hazardous waste is not fed and hazardous waste does not remain in the
combustion chamber); and (2) stops complying with the proposed
standards and begins complying with other applicable MACT standards
(i.e., cement kilns must comply with the MACT standards, when
promulgated, for kilns that do not burn hazardous waste). In addition,
today's rule would require sources that terminate hazardous waste
burning to notify the Administrator in writing within 5 days of the
termination.
Such sources could begin burning hazardous waste again under the
following conditions: (1) The source must comply with the MACT
standards applicable to new sources; (2) the source must submit a
notification of compliance with the standards (based on a comprehensive
performance test); and (3) prior to submitting the notification of
compliance, the source cannot burn hazardous waste for more than a
total of 720 hours, and hazardous waste may be burned only for purposes
of emissions pretesting (i.e., in preparation for the comprehensive
performance test) or comprehensive performance testing.
We are taking this position regarding termination of waste burning
to avoid the implementation and enforcement complications that could
result if a source could claim that it was not subject to the proposed
regulations during those periods of time that it was not burning
hazardous waste. Without these requirements, a source could vacillate
at will between being regulated and unregulated (or for CKs, between
being subject to regulation as a hazardous waste-burning kiln versus a
non-hazardous waste-burning kiln). We invite comment on whether these
requirements are reasonable and appropriate to address the Agency's
implementation and enforcement concerns.
II. Selection of Format for the Proposed Standards
A. Format of the Standard
When EPA regulates a source, it must determine on a case-by-case
basis what format the standards are. This section explains the reasons
why EPA chose the format it did for this specific source category. Due
to differing situations in other cases, other formats may be chosen for
other source categories.
1. Units
EPA investigated four formats for use in expressing today's
proposed standards: mass-based emissions; calculated mass-based
emissions; percent reduction; and concentration-based. The Agency
ultimately selected concentration-based standards for the reasons
discussed below.
The mass-based approach would set a limit of mass emissions per
unit time, i.e., kg/hr, lb/hr, etc. This approach was rejected because
it is inherently incompatible with technology based standards for
several reasons. First, a mass-based standard does not assure good
control at small facilities. Small facilities have lower flow rates,
would be allowed higher concentration of emissions, and thus could meet
a standard with no or minimal technological control. Also, it produces
an undue burden on larger facilities in that they would have to install
controls and small facilities would not. One potential consequence is
that it would cause an incentive for more small facilities, causing an
increase in emissions nationally. For these reasons, this option was
not chosen.
An alternate to the mass-based approach is the calculated mass-
based approach. This would involve EPA determining some appropriately
low level of metals and chlorine feed, multiplying that by a system
removal efficiency factor, and issuing the result as a mass-based
limit. One concern with this approach is EPA does not know what
feedrate would be appropriate. Any feedrate could be construed as
arbitrary. Also, the approach would result in a mass-based limit which
does not address concerns described in the preceding paragraph. It also
does not address how to set the other standards: CO, HC, PM, and
dioxin/furans. For these reasons, this option was not chosen.
A third approach is to set the standards based on a specified
percent reduction. This comports well with a technology-based approach
because it deals directly with determining what technology performs
most efficiently. However, there are problems with this approach.
First, it is difficult to determine where the percent reduction should
be applied: feed to stack, across the APCD train, or across a specific
control device. Use of feed to stack percent reductions present a
difficulty due to the measurement variability of feed samples and stack
emissions. APCD train or device specific percent reductions would be
difficult to implement. Facilities are not configured to sample inlet
emissions to the APCD train or to a specific APCD. Thus, facilities
would have to be reconfigured to allow inlet sampling. Stack sampling
would be required at both the outlet and, possibly, multiple inlet
points. This would significantly increase the testing burden. In
addition, implementation of any approach based on percent reduction
would involve substantial and expensive monitoring of operating
parameters to ensure that the specified percent reduction occurs during
operation. For these reasons, this approach was not chosen.
[[Page 17378]]
The approach that was chosen for these source categories is to set
concentration-based standards. This approach is consistent with how EPA
has historically based air emission standards. It favorably addresses
the problems of the other options. However, it does allow larger
facilities to emit higher mass emissions of HAPs. But mass-based levels
would result in higher emissions nationally by encouraging more smaller
facilities (see previous paragraph). This tradeoff, having higher mass
emissions at larger facilities but lower emissions nationally, was
considered acceptable for this proposal. Concentration based approaches
are also easier to implement and do not necessarily rely on the setting
of operating limits. For this reason, concentration-based standards are
regarded as preferable to the other options, and was chosen on that
basis.
It is possible that other units could be chosen for other source
categories. As explained in the introductory paragraph this is
consistent because other units might be more appropriate for other
source categories.
2. Correction to 7 Percent Oxygen and 20 deg. C
All standards are corrected to 7 percent oxygen and 20 deg. C. This
is because the data EPA used to derive the standards were corrected in
this manner. This is also consistent with the correction used for BIFs,
hazardous waste incinerators, MWCs, and MWIs.
3. Significant Figures and Rounding
All standards proposed here are expressed to two significant
figures.
For the purposes of rounding, we propose to require the use of ASTM
procedure E-29-90 or its successor. This procedure is the American
standard for rounding. Rounding shall be avoided prior to rounding for
the reported result.
B. Averaging Periods
Averaging periods are the time periods over which emissions or
feedstream and operating parameters are set. These periods require
consideration because of the inherent variability associated with the
operation of complying (i.e., properly designed and operated) MACT
devices. As noted above, facilities normally operate within certain
limits but do have emissions above and below these normal levels due to
the natural variability associated with the operation of a facility.
EPA must account for this variability when promulgating technology-
based standards. See, e.g., FMC Corp. v. Train, 538 F.2d 973, 986 (4th
Cir. 1976). If EPA were to establish a ``not-to-be-exceeded'' limit,
that limit would invariably be higher than if the limit were expressed
as an average emission level. That would tend to encourage higher
emitting, but low variability devices since they could meet the not-to-
exceed standard.
For instance, say EPA is considering establishing a standard on: an
instantaneous basis; a one hour average; and a 12-hour average. Also,
assume that the complying MACT facility has average emissions of 5 and
short-term perturbations as high as 300. In this case equally stringent
emissions levels could be: 300 on an instantaneous basis; on the order
of 10 for an hourly average; or closer to 5 for the 12-hour average. If
the limit were established at 300 on an instantaneous basis, this could
significantly favor a facility that has high perturbations less than
300, but average emissions of 250 (assuming the facility with average
emissions of 250 could meet the instantaneous limit, 300, with fewer
controls.) This facility would emit 50 times more of that HAP than a
facility operating at an emission average of 5, but would still comply
with the standard. To address the problem of setting limits on an
instantaneous basis, emissions and feedstream and operating limits are
established on the average with specified averaging periods.
1. Manual Methods
The MACT standards for HWCs (except those for HC and CO) were based
on the average of data from three test runs during which emissions were
measured by manual methods. EPA thus proposes that compliance be based
on the average of three manual methods test runs to be consistent with
data used to establish the standards. Chemical Waste Management v. EPA,
976 F.2d 2, 34 (D.C. Cir. 1992) (Noting that this is an inherently
reasonable approach and is consistent with the standard approach for
compliance under the Part 63 MACT standards.)
The standard could be set in such a way as to require all three
runs to be less than the standard. Such a standard would be derived by
choosing the highest data point from three manual test runs and would
result in an emission level higher than those proposed. The ``not-to-
be-exceeded'' approach was considered problematic for reasons just
described, so averaging was chosen.
Manual methods sample facility exhaust emissions for a period of
time. The minimum length of time required to sample is specified
indirectly by the manual method in the form of collection or gas flow
specifications. The results of the manual method test are reported as
an average over the sampling period. Therefore for manual method test
runs, the averaging period is the sampling period over which the sample
was collected.
EPA proposes no specific averaging period here for manual method
test runs, with one caveat discussed below. Instead EPA proposes to
rely on the minimum sampling volumes or collected sample (whichever the
method requires) specified by the manual methods. EPA invites comment
on whether minimum sampling periods for manual methods should be
specified directly.
EPA is proposing a three hour minimum sampling time for method
0023A. Three hours is also the minimum sampling period stated in method
23 to Part 60, appendix A. EPA is proposing a minimum sampling time in
order to ensure that each D/F run samples long enough to obtain
adequate samples of the various congeners to determine compliance with
the TEQ standard. This issue is important here because there is an
inconsistency between air rules and RCRA rules regarding how to treat
nondetected congeners when calculating the TEQ.
The document which defines the TEQ calculation, ``Interim
Procedures for Estimating Risks Associated with Exposures to Mixtures
of Chlorinated Dibenzo-p-Dioxins (CDDs and CDFs) and 1989 Update''
(EPA/625/3-89/016, March 1989), uses in its examples the assumption
that all non-detects are zero. Also, Method 23 of Part 60 Appendix A,
the method used by air programs for determining total D/F congeners,
similarly states in Section 9, titled Calculations:
Any PCDD's or PCDF's that are reported as nondetected (below the
MDL) shall be counted as zero for the purpose of calculating the
total concentration of PCDD's and PCDF's in the sample.
Therefore, many assume that nondetects are zero for the purposes of
calculating site specific TEQs.
Unfortunately, RCRA programs in most instances use the nondetect
value, not zero, in the calculation of the TEQ. (See BIF method 23
found in Part 266, Appendix IX, section 3.4.) Since this rule would be
promulgated under both RCRA and CAA authority, this issue needs to be
resolved.
The Agency believes a facility will have to measure for 20 minutes
per run using SW-846 method 0023a to obtain enough sample to be useful
for the TEQ calculation. This leads EPA to believe that enough sample
will be collected during a three hour run to assure that
[[Page 17379]]
nondetected congeners are indeed not present. If a source complies with
the minimum sampling period and still has non-detects, then EPA
proposes allowing non-detects to be assumed to be zero.
This would also apply to other methods which have passed the Method
301 validation procedures and EPA has agreed are acceptable. In the
case of other methods, the facility would assume that non-detects are
zero if the method accumulates the same amount or more sample than
Method 0023A would in a three hour run. If a source chooses not to
comply with the three hour minimum, EPA would mandate that non-detected
congeners be assumed to be present at the detection level for the
purposes of the TEQ calculation.
EPA specifically invites comments on the selection of the proposed
minimum sampling time for the D/F method and the assumed concentration
of nondetected congeners in the calculation of the TEQ.
2. Continuous Emissions Monitoring Systems (CEMS)
EPA is proposing to require the use of five CEMS--CO, HC, O2,
Hg, and PM--and to allow the use of CEMS for SVM, LVM, HCl, and
Cl2. Presently, for cement kilns and LWAKs, continuous emission
monitoring of O2 and CO (or HC) is required under the BIF rule (40
CFR 266.103(c)(1)(v)). Emission limits and their associated averaging
period must be established for all of these pollutants (except for
O2) in keeping with the nature of compliance with a CEMS. (The
O2 CEMS is used to continuously correct the CEMS readings for the
other pollutants to 7 percent O2. There is no emission limit
specific to O2.) Hourly rolling average emissions data are
available to establish emission limits for CO and HC on an hourly-
rolling average.
Only manual method stack emissions data, however, are available to
establish appropriate emission limits and averaging periods for the
other standards: Hg, PM,42 SVM, LVM, and HCl and Cl2. This
presents a unique issue for the Agency to resolve since, in most cases,
EPA promulgates CEMS standards by collecting CEMS emissions data from
facilities run under ``normal'' conditions. The Agency would use this
CEMS data to calculate a statistically based CEMS emission standard,
assuming some confidence interval and number of annual exceedances.
Since no ``normal'' CEMS data exists, but worst-case manual test data
from trial burns and compliance tests does, an alternate approach must
be developed to derive a CEMS emission standard an its associated
averaging period.
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\42\ Note that the PM CEM is also used as an operating parameter
for PM APCD efficiency and that additional averaging periods apply
during normal operation. See Part Five, Section II.C.7. titled
``Particulate Matter'' for more information.
---------------------------------------------------------------------------
a. Approach to Establishing Averaging Periods for Hg, PM,43
SVM, LVM, HCl and Cl2 CEMS. One important issue concerning the
data is that it was obtained from trials burn and compliance test
results (similar to the comprehensive performance test, described in
section III of Part Five). These are generally worst-case tests
facilities used to establish operating limits under the BIF and
Incinerator rules. Facilities must be in compliance with all standards
at all times they are burning hazardous waste. Therefore, the emissions
represented by this data are the highest emissions the facility could
experience and be in compliance with the current BIF and incinerator
rules. In other words, the emissions data represents a not-to-be-
exceeded emission level for the given facility.
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\43\ Note that the PM CEM is also used as an operating parameter
for PM APCD efficiency and that additional averaging periods apply
during normal operation. See Part Five, Section II.C.7. titled
``Particulate Matter'' for more information.
---------------------------------------------------------------------------
Now, let us examine how a facility would comply with today's
proposed emission standards if they were not to use a CEMS, but by
performing a comprehensive performance test and complying with the
standards using operating parameter limits. As a result of today's
proposed rule and as was the case in the BIF and incinerator rules, EPA
believes facilities will conduct a comprehensive performance test in
the same way current trial burns and compliance tests are conducted.
That is they will attempt to get the widest operating envelope possible
by intentionally running the facility under conditions which will
maximize emissions (by practices such as maximizing feed-rates, running
control devices less effectively, etc.) and yet not exceed any
applicable emission standards. Facilities will use the operating data
from the comprehensive test to establish and continuously monitor
operating limits for feedrate and device parameters. This defines the
facility's operating envelope. During normal operation, owner/operators
will operate in such a way that the facility is performing better than
the operating limits established during the comprehensive performance
test. Since exceedances of operating limits established during the
comprehensive performance test are a de facto violation of the
corresponding standard, this means that the emissions during normal
operation will at all times be lower than those during the
comprehensive test.
When complying with today's proposed standards using a CEMS, it is
important that facilities using a CEMS not be at a disadvantage
relative to facilities using operating parameter limits. There are two
ways a disadvantage could occur: when the emission standard is
numerically less and/or the averaging period is shorter. In the case of
manual stack tests, the averaging period is the stack sampling time.
Therefore, the CEMS emission limit would be equal in stringency to the
manual stack test limit if they both had the same numerical value and
the CEMS averaging period were equal to the sampling period for the
manual method.
Also, EPA believes facilities have a number of advantages using
CEMS. First, the assumptions to assure compliance are fewer and less
conservative (direct measure of the standard is the top of the
monitoring hierarchy; see section II.A. of Part Five.) CEMS are less
intrusive on the facility than operating parameter limits. Most
importantly, CEMS mean facilities need to monitor only one emissions
parameter to assure compliance rather than multiple operating limits,
often relevant to more than one standard.44
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\44\ For example, an exceedance of an operating parameter limit
used to ensure compliance with the dioxin, mercury, SVM, LVM, and
HCl and Cl2 standards would be a violation of all those
standards. If a CEM were used for one or more of these standards, a
violation would only occur if the CEM limit were exceeded.
---------------------------------------------------------------------------
In summary, regardless of whether CEMS or operating limits are
used, both continually assure that the facility is meeting the
standard(s) at all times. CEMS are an alternate, more direct, method of
confirming a state of performance than are continuously monitored
operating parameter limits established through a comprehensive test. A
facility which complies with the standards in today's proposed rule
would experience its highest emissions during a comprehensive
performance test, when the facility establishes its operating envelope
to ensure it is in compliance with the standards at all times.
Therefore, a CEMS limit is equally stringent to a standard for a
comprehensive performance test if it is numerically equal and has the
same averaging period. For comprehensive performance tests, the
averaging period is the sampling time for the manual method. Therefore,
it is proposed that the CEMS standards be the same numerical limits
established for manual method comprehensive performance tests with the
averaging period equal to
[[Page 17380]]
the sampling period for three manual method test runs.
b. Averaging Periods for CO and HC CEMS. As stated previously, the
data used to derive today's proposed CO and HC standards proposed are
not manual methods data, but continuous emissions data based on a one-
hour rolling average. To be consistent with the data used to derive the
standards, it is proposed that the averaging periods for CO and HC CEMS
standards remain one-hour.
c. Averaging Periods for Other CEMS. Based on the discussion of
subsection I above, EPA proposes the following CEMS averaging periods
for CEMS. The numerical standard is the same as those proposed in
sections III through V of this part.
Three main assumptions were used in determining how long a facility
would have to sample to achieve the minimum levels specified in the
manual methods. They are assumptions for: sample flow rate; flue gas
oxygen content; and the detection limit or specified sample collection
specified in the method. For sample flow rate, EPA assumed a flow rate
of 0.5 scfm because this is either what is directly stated as the flow
rate in the methods or it is used by convention.
The Agency also assumed that the oxygen concentration in the flue
gas was 7 percent, the basis of today's standards. Oxygen
concentrations in the flue gas can change greatly, but EPA believes
that the derived sampling time is elastic relative to the assumed
oxygen concentration. In other words, the sampling times would change
roughly five to ten per cent over the range of oxygen concentrations
experienced by HWCs. This is not significant relative to other
assumptions made here, so a 7 percent oxygen concentration was assumed.
Finally, each method specifies a minimum analytical detection limit
or sample collection. We assumed that a test operator would collect
three times what is prescribed in the method to account for facility
variability, unknowns at a given site, etc. This is a conventional
approach used by testing contractors. This will be referred to below as
the ``collected sample.''
There are other issues which need to be addressed as well. One CEMS
can be used to comply with more than one standard and standards can
vary from subcategory to subcategory. Therefore, EPA proposes that the
sampling time used to derive the averaging period be the longest
sampling time which relates to the CEM averaging period. For an
example, see the discussion on the Hg and multi-metals CEM standards,
below.
Manual methods tests do not run on-the-hour, so an averaging
periods with some fraction of an hour would result if rounding were not
used. EPA believes it is reasonable and simpler to have integer value
hourly averages. Since the direct measure of a standard at the stack is
at the top of the monitoring hierarchy, a less conservative approach is
warranted in this case, so EPA proposes that averaging periods for CEMS
be rounded up to the nearest hour. (See section II.A. of Part Five for
more information on the monitoring hierarchy.)
Also, a resulting averaging period may be inappropriately short,
i.e., less than one hour. In this case EPA would establish an averaging
period of one-hour. This is reasonable since the averages for operating
parameters to control average emissions are one-hour. (See section
II.B.1. of Part Five for a discussion of averages for operating
parameters.) Monitoring of a standard continuously at the stack is at
the top of the monitoring hierarchy, while establishing operating
parameter limits is at the bottom. It would be inconsistent if an
averaging period for CEMS were less than those for operating parameter
limits, so a one-hour average will be proposed in this case.
For mercury (Hg) and multi-metal CEMS, it is proposed that the
averaging period be ten hours. SW-846 method 0060 would be the manual
method used to comply with these standards if a CEM were not used.
Emission standards for these HAP categories vary greatly from HAP-to-
HAP and within a HAP, from subcategory-to-subcategory. But the proposed
SVM standard for LWAKs results in the longest sample collection time.
EPA believes that an LWAK will have to sample for approximately 200
minutes per run to collect 15 g of sample to be in compliance
with the LWAK SVM standard. Three runs of 200 minute duration is 600
minutes, or ten hours.
For the HCl and Cl2 standard, it is proposed that the CEMS
averaging period be one hour. In this case, EPA has determined that a
facility would have to sample less than ten minutes per run to collect
the minimum amount, 300 g, of sample specified by the method.
If three times this sampling time were used to establish the averaging
time, it would result in one of roughly 30 minutes. This is
unreasonable for a CEMS averaging period, so EPA is proposing that the
averaging period be one hour.
Finally, it is proposed that the PM CEMS averaging period be two
hours. This is because a facility would have to sample for roughly 30
minutes per run to collect the minimum amount, 30 mg, of particulate
specified by the method. Three times this sampling time is 1.5 hours,
so after rounding an averaging period of two hours is proposed.
Table IV.2.1 summarizes the CEMS averaging period for the various
CEMS emission standards.
Table IV.2.1.--Averaging Periods for CEMS Standards
------------------------------------------------------------------------
HAP or standard CEMS averaging period
------------------------------------------------------------------------
PM......................................... 2 hours.
Mercury (Hg)............................... 10 hours.
SVM........................................ 10 hours.
LVM........................................ 10 hours.
HCl and Cl2............................ 1 hour.
CO......................................... 1 hour.
HC......................................... 1 hour.
------------------------------------------------------------------------
d. All Averages are Rolling Averages. All CEMS averaging periods
are on a rolling-basis. In other words, each time a sample is recorded,
a new rolling average is calculated using the new sample and all
previous samples obtained during the specified averaging period. If
sample results are recorded every minute and the averaging period is
one hour, then the most recent sample is averaged together with the
results of the previous 59 samples to obtain the hourly rolling
average. When there are not enough data to obtain a rolling average,
one of two approaches would be used. We propose that for short-term
interruptions of the rolling average that the rolling average ``pick-
up'' where it left off, i.e., consider the one-minute average
immediately prior to the interruption to be the one minute average that
occurred prior to the current one-minute average. For longer term
interruptions, all available one minute averages would be averaged
together until the time period since the start of the rolling average
equals the averaging period for that parameter. Then there is enough
data to perform the rolling average as usual, and the rolling average
would continue as normal. For more information on the use of CEMS and
the rolling average, see Part Five, Section II.C. ``Compliance
Monitoring Requirements'' and the proposed regulations, Appendix J to
Part 60.
3. Feedstream and Operating Limits
Today, EPA is proposing specific monitoring requirements to ensure
facilities are in compliance with the standards during normal
operation. Some of these monitoring requirements require setting limits
on feedstream or operating parameters. These limits will
[[Page 17381]]
be set on an average. Other limits would be instantaneous limits, such
as those for fugitive process emissions.
It is proposed that four averaging periods be used for feedstream
and operating limits: twelve hour, one hour, ten minutes, and
instantaneous. All averages would be calculated on a rolling-average
basis with measurements taken every 15 seconds to obtain a one minute
average. The one minute averages are used to obtain the twelve hour,
one hour or ten minute rolling average. The use of one-minute averages,
i.e., the average of the previous 15 second averages within that
minute, is the current practice for HWCs. ``Instantaneous'' limits are
just that, values not to be exceeded at any time. Averaging does not
occur for ``instantaneous'' values. These definitions supersede
requirements in the Part 63 general provisions, which are less
stringent. Consult chapter 5, volume IV of the Technical Background
Document for more information regarding EPA's choice of the time
duration for averaging periods.
For discussion on what operating limits EPA is proposing and what
the averaging period will be for particular operating limits, see
section II of Part Five of this preamble.
III. Incinerators: Basis and Level for the Proposed NESHAP Standards
for New and Existing Sources
Today's proposal would establish maximum achievable control
technology (MACT) emission standards for dioxins/furans, mercury,
semivolatile metals (cadmium and lead), low volatile metals (arsenic,
beryllium, chromium and antimony), hydrochloric acid and chlorine
(combined), particulate matter, carbon monoxide, and hydrocarbons from
existing and new hazardous waste incinerators (HWIs). See proposed
Sec. 63.1203. The following discussion addresses how MACT floor and
beyond-the-floor (BTF) levels were established for each HAP, and EPA's
rationale for the proposed standards. The Agency's overall procedural
approach for MACT determinations has been discussed in Part Three,
Sections V and VI for existing sources and in Section VII for new
sources.
To conduct the MACT floor analyses presented today, the Agency
compiled available data from hazardous waste-burning incinerators: both
commercial as well as on-site facilities. As discussed earlier, the
vast majority of these data were generated during trial burns to
demonstrate compliance with existing RCRA standards at 40 CFR Part 264,
Subpart O. Therefore, the data were obtained under proper QA/QC
procedures. These emissions data, however, represent worse-case
emissions that cannot be exceeded (because limits on operating
parameters are based on operations during the trial burn). As noted
earlier, the Agency invites commenters to submit data that reflect more
normal, day-to-day operations and emissions. This will enable the
Agency, among other things, to be better able to distinguish among
facilities that are now included in the expanded MACT floor pool but
which, upon closer inspection and with better data, may not be actually
employing the identified floor controls.
A. Summary of MACT Standards for Existing Incinerators
This section summarizes EPA's proposed emission levels for existing
incinerators for each HAP, HAP group, or HAP surrogate. The proposed
emission standards for HWIs are presented in the table below:
Table IV.3.A.1.--Proposed MACT Standards for Existing Incinerators
------------------------------------------------------------------------
HAP or HAP surrogate Proposed standards \1\
------------------------------------------------------------------------
Dioxin/furans........................ 0.20 ng/dscm TEQ.
Particulate Matter................... 0.030 gr/dscf.
(69 mg/dscm).
Mercury.............................. 50 g/dscm.
SVM [Cd, Pb]......................... 270 g/dscm.
LVM [As, Be, Cr, Sb]................. 210 g/dscm.
HCl + Cl2............................ 280 ppmv.
CO................................... 100 ppmv.
HC................................... 12 ppmv.
------------------------------------------------------------------------
\1\ All emission levels are corrected to 7 percent O2.
1. Dioxins and Furans (D/Fs)
a. MACT Floor. The Agency's analysis of dioxin/furan (D/F)
emissions from HWCs and other combustion devices (e.g., municipal waste
combustors and medical waste incinerators) indicates that temperature
of combustion gas at the inlet to the particulate matter (PM) control
device can have a major effect on D/F emissions.45 D/F emissions
generally decrease as the gas temperature of the PM control device
decreases, and emissions are lowest when the gas temperature of the PM
control device is below the optimum temperature window for D/F
formation--450 to 650 deg.F.46 Given that incinerators are
equipped with both wet and dry PM control devices that operate under a
range of temperatures, the Agency is identifying a MACT floor for D/F
based on temperature control at the inlet to the PM control device.
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\45\ USEPA, ``Draft Technical Support Document For HWC MACT
Standards, Volume III: Selection of Proposed MACT Standards and
Technologies'', February 1996.
\46\ For example, during compliance testing of a cement kiln, D/
F emissions exceeded 1.7 ng/dscm (TEQ) at a ESP temperature of
435 deg. F.
---------------------------------------------------------------------------
Incinerators emitting D/F at or below levels emitted by the median
of the best performing 12 percent of incinerators have combustion gas
temperatures below 400 deg. F. These best performing sources were
equipped with venturi scrubbers to control PM. The gas temperature of
the wet air pollution control system for one source was 163 deg. F; gas
temperature data for the other best performing sources were not
available. Although gas temperatures at a wet PM control device would
normally be less than 200 deg. F, temperatures could be higher in the
presence of acid gases such as HCl and SO2. Consequently, the
Agency believes that it would be reasonable and appropriate to
generalize that gas temperatures of wet PM control devices are less
than 400 deg. F.
The Agency evaluated D/F emissions from all incinerators that are
equipped with wet PM control systems. Average D/F emissions for test
conditions ranged from 0.01 ng/dscm (TEQ) to 39 ng/dscm (TEQ). D/F
emissions were as high as 3.5 ng/dscm (TEQ) for incinerators that were
not burning substantial levels of known D/F precursors or were not
equipped with a waste heat boiler (WHB). (It is hypothesized that WHB-
equipped incinerators may have high (uncontrolled) D/F emissions
because D/F may be formed on particulate attached to boiler tubes as
combustion gases pass through the optimum temperature window (450-
650 deg. F) for D/F formation.) WHB-equipped incinerators using wet PM
control devices had D/F emissions ranging from 0.4 to 8 ng/dscm (TEQ),
and an incinerator equipped with a wet PM control device burning waste
comprised of approximately 30 percent PCBs had D/F emissions of 39 ng/
dscm (TEQ).
The Agency is consequently identifying temperature control to below
400 deg. F at the PM control device as the MACT floor. Given that
approximately 45 percent of test conditions in our database have
average D/F emissions below 0.20 ng/dscm (TEQ), we believe that it is
appropriate to express the floor as ``0.20 ng/dscm (TEQ), or
temperature at the PM control device not to exceed 400 deg. F''. This
would allow sources that operate at temperatures above 400 deg. F but
that achieve the same D/F emissions as 45 percent of sources that
operate below 400 deg. F to meet the standard without incurring the
expense of
[[Page 17382]]
lowering the PM control device gas temperature.
EPA estimates that 75 percent of incinerators are currently meeting
the floor level. The annualized cost for the remaining incinerators to
reduce D/F emissions to 0.20 ng/dscm (TEQ) or control gas temperature
at the PM control device to below 400 deg. F would be $3.0 million.
Achievement of the floor levels would reduce D/F TEQ emissions
nationally by 35 g/yr.
b. Beyond-the-Floor (BTF) Considerations. The Agency has identified
activated carbon injection (CI) operated at gas temperatures less than
400 deg. F as BTF control for D/F for incinerators.47 CI is
currently used by a commercial hazardous waste incinerators to achieve
emission levels routinely (based on quarterly stack testing) of less
than 0.20 ng/dscm (TEQ). CI is also used to reduce D/F emissions from
several municipal and medical waste incinerators (MWIs) in a similar
manner.
---------------------------------------------------------------------------
\47\ We note that incinerators using wet PM control systems
would need to reheat the combustion gas before injecting the carbon.
This is because CI is not efficient at D/F (or Hg) removal at gas
temperatures below the dew point. Gas reheating in these situations
was considered in estimating the cost of compliance with the
proposed standards.
---------------------------------------------------------------------------
CI has been demonstrated to be routinely effective at removing
greater than 95 percent of D/F and some tests have demonstrated a
removal efficiency exceeding 99 percent at gas temperatures of 400 deg.
F or below.48 To determine a BTF emission level, the Agency
considered the emission levels that could result from gas temperature
control to less than 400 deg. F combined with CI.
---------------------------------------------------------------------------
\48\ USEPA, ``Draft Technical Support Document For HWC MACT
Standards, Volume III: Selection of Proposed MACT Standards and
Technologies'', February 1996.
---------------------------------------------------------------------------
To estimate D/F emissions with temperature control combined with
CI, the Agency considered the range of emissions from sources in the
MACT floor database, as discussed above. Incinerators that are not
equipped with a WHB and not burning high levels of D/F precursors (the
vast majority of incinerators) could be expected to achieve D/F
emissions of less than 3.5 ng/dscm (TEQ) with temperature control only.
These sources could be expected to achieve D/F emissions of below 0.18
ng/dscm (TEQ) when using CI assuming a fairly conservative removal
efficiency of 95 percent.
There are three sources in our database equipped with WHBs. One
currently uses CI to achieve D/F emissions below 0.20 ng/dscm (TEQ)
when controlling PM with an ESP operating below 400 deg. F. Another
source had D/F emissions of 0.56 ng/dscm (TEQ) when controlling PM with
a wet system. This source could be expected to achieve D/F emissions
below 0.03 ng/dscm (TEQ) using CI at a removal efficiency of 95
percent. The third WHB-equipped incinerator in our database had D/F
emissions of 8.0 ng/dscm (TEQ) when controlling PM with a wet system.
This source could be expected to achieve D/F emissions below 0.40 ng/
dscm using CI at a removal efficiency of 95 percent. We note, however,
that the feed to this source during testing comprised approximately 10
percent hexachlorophenol, a D/F precursor.
Finally, one incinerator in the database that controlled PM with a
wet system had D/F emissions of 39 ng/dscm (TEQ). This source could be
expected to achieve D/F emissions below 2 ng/dscm (TEQ) when using CI
at 95 percent efficiency. We note, however, that the feed to this
source during testing comprised approximately 30 percent PCBs, known D/
F precursors.
The Agency has considered this information and determined that it
would be reasonable and appropriate to establish 0.20 ng/dscm (TEQ) as
an emission level that is achievable with BTF control. Although two
sources in our database that fed (during testing) high levels of D/F
precursors may not have been able to achieve that level if they had
been equipped with CI, we believe that those sources could achieve a
level of 0.20 ng by reducing the feedrate of D/F precursors.
We note that, because we have assumed a fairly conservative CI
removal efficiency of 95 percent to identify the 0.20 ng/dscm BTF
level, we believe that this adequately accounts for emissions
variability that would be experienced at a given source attempting to
operate under constant conditions (e.g., as during a performance test).
That is, because CI removal efficiency is likely to be up to or greater
than 99 percent, we believe that it is not necessary to add a
statistically-derived variability factor to the 0.20 ng/dscm BTF level
to account for emissions variability. Accordingly, the 0.20 ng/dscm
(TEQ) BTF level is proposed as the emission standard.
We invite comment on this issue, and note that if a statistically-
derived variability factor were deemed appropriate, the BTF level of
0.20 ng/dscm would be expressed as a standard of 0.31 ng/dscm (TEQ). We
note, however, that under this approach, it may be appropriate to use a
less conservative CI removal efficiency (i.e., because emissions
variability would be accounted for using statistics rather than in the
engineering decision to use a conservative CI removal efficiency), thus
lowering the 0.20 ng/dscm level to approximately 0.1 ng/dscm (TEQ). If
so, the BTF standard would be approximately 0.21 ng/dscm (TEQ) (i.e.,
virtually identical to the proposed standard) after considering a
statistically-derived variability factor.
EPA estimates that 50 percent of incinerators are currently meeting
a BTF level of 0.20 ng/dscm (TEQ). The incremental annualized cost for
the remaining incinerators to meet this BTF level rather than comply
with the floor controls would be $26.2 million, and would provide an
incremental national reduction of 38 g/yr in D/F TEQ emissions over the
floor level. This represents an overall reduction of about 95 percent
compared to baseline D/F emissions of 77 g/year.
EPA has determined that proposing a BTF MACT standard is warranted
and a number of factors support the proposed BTF level of 0.20 ng/dscm
(TEQ). D/F are some of the most toxic compounds known due to their
bioaccumulation potential and wide range of health effects at
exceedingly low doses, including carcinogenesis. Exposure via indirect
pathways was in fact a chief reason Congress singled out D/F for
priority MACT control in section 112(c)(6). See S. Rep. No. 228, 101st
Cong. 1st Sess. at 154-155 (1990). As discussed elsewhere in today's
preamble (and as qualified by the discussion below regarding small
incinerators), EPA's risk analysis developed for purposes of RCRA in
fact shows that D/F emissions from hazardous waste incinerators could
pose significant risks by indirect exposure pathways and that these
risks would be reduced by BTF controls. EPA is expressly authorized to
consider this non-air environmental benefit in determining whether to
adopt a BTF level. CAA section 112(d)(2).
As discussed in Part Seven of the preamble, the cost-effectiveness
of the BTF level for small on-site incinerators may be high. This is
because on-site incinerators are generally smaller than commercial
incinerators, have lower gas flow rates, and therefore have lower mass
emission rates of D/F. Thus, the cost per gram of D/F TEQ removed for
small incinerators is greater than for large (on-site and commercial)
incinerators. Accordingly, the Agency invites data and comment on: (1)
whether the BTF level is cost-effective for small incinerators; and (2)
whether the final rule should establish MACT standards at the floor
level (i.e., 0.20 ng/dscm (TEQ), or 400 deg. F) for these small
[[Page 17383]]
incinerators.49 50 Under this approach, the Agency would use the
same definition of small incinerator used to identify incinerators
subject to less frequent performance testing--incinerators with gas
flow rates less than 23,127 acfm.51
---------------------------------------------------------------------------
\49\ See also discussion in Part Four, Section I (Selection of
Source Categories and Pollutants), regarding whether the Agency
should subdivide incinerators by size and promulgate separate floor
standards (and BTF standards, if warranted).
\50\ If after review of comments and further analysis the Agency
determines that subdividing incinerators is not appropriate but,
because of cost-effectiveness considerations, BTF levels are not
warranted for all types of incinerators, the Agency invites comment
on whether such cost-effectiveness and BTF decisions should be based
on incinerator size or whether the incinerator is a commercial or
on-site unit.
\51\ We also use this definition to request (elsewhere in the
text) comment on whether the requirement to use Hg and PM CEMS for
compliance monitoring should be relaxed or waived for small
incinerators.
---------------------------------------------------------------------------
EPA notes further that the control technology on which the proposed
BTF standard is based, carbon injection, also controls mercury. The
ability and efficiencies of controlling two such high toxicity HAPs
with the same highly-efficient control technology is an important
factor in the Agency's decision to propose a BTF standard. The Agency
notes further that the absolute cost of achieving the proposed standard
is relatively low, particularly considering the toxicity of D/F (as
well as mercury, which, as just noted, would also be controlled). For
example, the proposed BTF levels would result in annualized costs of
$27 million to all HWIs or $15 per ton of hazardous waste burned.
Finally, EPA's initial view is that it may be necessary to adopt
further controls under RCRA to control D/F if it did not adopt the BTF
level. This would defeat one of the purposes of this proposal--to avoid
imposing emission standards under both statutes for these sources
wherever possible. These risks would, however, be reduced to acceptable
levels if emission levels are reduced to the proposed BTF level of 0.20
ng/dscm (TEQ).
2. Particulate Matter
a. MACT Floor. The Agency has a database for PM emissions from 74
HWIs that indicates a range (by test condition average) from 0.0003 gr/
dscf to 1.9 gr/dscf. For MACT determination, the median of the best
performing 12 percent of the HWIs in the MACT pool were analyzed and
found to be using the following APCDs to control PM: (1) A fabric
filter (with an air to cloth ratio of less than 10.0 acfm/ft2);
and (2) an ionizing wet scrubber (IWS) in combination with a venturi-
scrubber. Accordingly, these APCDs were tentatively designated as the
MACT floor technologies. To identify an emission level that these
technologies could be expected to achieve routinely, the Agency
examined the emissions from all incinerators (in the database) that
were equipped with these PM control devices. A MACT floor level of 240
mg/dscm (0.107 grains/dscf) resulted from the analysis based on
considerations discussed in Part Three, Section V, above.
This level, however, is higher than the current federal standard of
180 mg/dscm (0.08 grains/dscf).\52\ Thus, the Agency is not proposing
to use the statistically-derived approach to identify the MACT floor
emission level. The Agency has regulated PM emissions from hazardous
waste incinerators under RCRA (40 CFR 264.343(c)) since 1981 and all
RCRA-permitted incinerators have been required to meet the federal
standard of 0.08 gr/dscf (180 mg/dscm). The Agency, therefore, is
identifying the MACT floor at the regulated level of 180 mg/dscm.
---------------------------------------------------------------------------
\52\ This anomalous result is apparently attributable to: (1)
inability to consider emissions from only those HWIs truly using
MACT floor control (because of inadequate data to properly
characterize the design, operation, and maintenance of the control
device); and (2) use of a variability factor that is based on
emissions variability (during trial burn testing) that may be much
higher than many sources actually experience.
---------------------------------------------------------------------------
The APCDs commonly used at HWIs to control PM to the current RCRA
standard are fabric filters, ESPs, IWSs, and venturi-scrubbers.
Accordingly, we have designated these technologies as MACT floor for PM
control. Approximately 95 percent of all test conditions in our
database have lower average levels (average over all runs of the test
condition) than the MACT floor level of 180 mg/dscm.\53\ This MACT
floor level will not impose any incremental burden on HWIs (except
compliance and related permitting costs) since it is the currently
enforceable level.
---------------------------------------------------------------------------
\53\ We presume that those few test conditions that exceeded the
180 mg/dscm standard occurred during failed trial burn tests.
---------------------------------------------------------------------------
b. Beyond-the-Floor Considerations. The Agency considered two
levels of more stringent BTF PM standards, 69 and 34 mg/dscm (0.03 and
0.015 gr/dscf), since well designed and well operated ESPs, IWSs, and
fabric filters can routinely achieve PM control at the 69 mg/dscm
level,\54\ while state-of-the-art ESPs, IWSs and FFs can achieve 34 mg/
dscm level. The Agency is proposing a BTF standard of 69 mg/dscm (0.03
grains/dscf) based on engineering evaluation of the emissions data from
HWIs. (We note that, as discussed in Sections IV and V below, it also
is consistent with the proposed standards for cement kilns and LWAKs).
Most of the HWIs having PM emissions between 69 to 180 mg/dscm (0.03 to
0.08 gr/dscf) range are likely to be using older APCDs that can be
upgraded to provide better PM control. Only 30 percent of all test
conditions \55\ in our database were found to have PM emissions greater
than the proposed BTF level of 69 mg/dscm (0.03 gr/dscf). Analysis of
the test data appeared to indicate that some sources operated under
poor, non-normal conditions during one test condition resulting in high
PM levels, while much lower PM emissions were achieved during other
test conditions. As noted elsewhere, the Agency is specifically
concerned that the nature of these test data (and the absence of more
detailed, routine operations and emissions data) has interfered with
our ability to derive MACT standards that appropriately reflect the
lower, day-to-day emissions achievements of the best performing
facilities. The Agency will continue to refine its analysis in this
regard, and we specifically invite data and comments on this issue.
---------------------------------------------------------------------------
\54\ We note also that, as discussed in the next section, cement
kilns with much higher inlet particulate loadings are currently
required to meet a 69 mg/dscm standard.
\55\ Representing 20 percent of the sources.
---------------------------------------------------------------------------
The Agency estimates that 9 percent of existing incinerators can
achieve the proposed BTF levels using design, operation and maintenance
upgrades of their APCDs, while 11 percent facilities would require
installation of new fabric filters or other equivalent APCD (e.g., ESP
or IWS). The national annualized cost to HWIs to comply with the
proposed BTF level would be $2.7 million and would provide an
incremental reduction of PM emissions of 839 tons/year (52 percent)
from the baseline emissions level of 1606 tons/year. Accordingly, the
Agency believes that a BTF level of 69 mg/dscm (0.03 gr/dscf) is
appropriate.
The performance of many APCDs can be improved to achieve a more
stringent PM BTF level of 34 mg/dscm by adopting good D/O/M practices;
in other cases, the APCD may have to be upgraded or replaced. Upgrades
include techniques for ESPs such as humidification or increasing the
plate area or power input, and for FFs, increasing cloth to air ratio
and pressure drop across bags, or retrofits to modern fabrics like
heavy woven fiberglass. The Agency is concerned, however, that the cost
of such retrofitting to achieve PM levels of 34 mg/dscm (0.015 gr/dscf)
[[Page 17384]]
could be substantial. We also note that PM is not a HAP, but rather a
surrogate for non-dioxin/furan HAPs adsorbed on to PM and for metal
HAPs not directly controlled by a MACT standard. These HAPS would be
controlled to some extent by other proposed standards (e.g., metal-
specific standards; CO and HC limits to control organic HAPs). For
these reasons, we believe that controlling PM to the proposed BTF level
of 69 mg/dscm (0.03 gr/dscf) is appropriate. In addition, we also note
that the Agency has no information that a lower PM standard would be
needed to satisfy RCRA requirements.
3. Mercury
a. MACT floor for mercury. Mercury (Hg) emissions from incinerators
are currently controlled by controlling the feedrate of Hg and by using
wet scrubbers (although such scrubbers are used primarily for acid gas
control). Wet scrubbers can remove soluble forms of mercury species
(e.g., HgCl).
The Agency's Hg emissions database from 29 HWIs indicates that
baseline Hg emissions range from 0.05 g/dscm to a high of
1,360 g/dscm. To identify MACT floor control, EPA determined
that sources with Hg emissions at or below the level emitted by the
median of the best performing 12 percent of sources were controlling Hg
using either: (1) Hg feedrate control expressed as a maximum
theoretical emission concentration (MTEC) \56\ of 19 g/dscm;
or (2) wet scrubbers coupled with an MTEC of 51 g/dscm.
Analysis of emissions from all incinerators in the database using these
or better controls (i.e., lower Hg feedrates expressed as lower MTECs)
resulted in a MACT floor level of 130 g/dscm.\57\ To meet this
floor level 99 percent of the time, EPA estimates that a source with
average emissions variability must be designed and operated to
routinely meet an emission level of 57 g/dscm.
---------------------------------------------------------------------------
\56\ MTEC is the Hg feedrate divided by the gas flow rate, and
is an approach to normalize Hg feedrate across sources.
\57\ As discussed above in the text, we added a within-test
condition emissions variability factor to the log-mean of the runs
for the test condition in the expanded MACT pool with the highest
average emission.
---------------------------------------------------------------------------
EPA estimates that approximately 70 percent of incinerators
currently meet the floor level. The annualized cost for the remaining
incinerators to meet the floor level is estimated to be $29.5 million,
and would reduce Hg emissions nationally by 7,166 lbs per year from the
baseline emissions level of 9,193 lbs per year.
b. Beyond-the-Floor Considerations. The Agency has considered two
alternative beyond-the-floor (BTF) controls for improved Hg control:
flue gas temperature reduction to 400 deg. F or less followed by either
activated carbon injection (CI) or carbon bed (CB). (As discussed in
the D/F section, we note that incinerators with PM control devices
operating below the dew point (e.g., venturi-scrubbers, ionizing wet
scrubbers) would have to reheat the combustion gas before using CI, and
would need to add a FF or other PM control device to remove the
injected carbon.) EPA believes that CI-controlled systems can routinely
achieve Hg emission reductions of 90 percent or better and that CB-
controlled systems can routinely achieve Hg emissions of 99 percent or
better.\58\
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\58\ USEPA, ``Draft Technical Support Document For HWC MACT
Standards, Volume III: Selection of Proposed MACT Standards and
Technologies'', February 1996. See also memo from Shiva Garg, EPA,
to the Docket (No. F-96-RCSP-FFFFF), dated February 22, 1996,
entitled ``Performance of Activated Carbon Injection On Dioxin/Furan
and Mercury Emissions.''
---------------------------------------------------------------------------
For CI-controlled systems, EPA has identified a BTF emission
standard of 50 g/dscm, assuming first that a source has
controlled its Hg emissions to only 300 g/dscm using a wet
scrubber and/or feed control, and second, a CI removal efficiency of 90
percent. (The BTF emission standard corresponds to a design level of 30
g/dscm, i.e., a level that the device is designed and operated
to achieve routinely.) \59\ For CB systems, the BTF standard would be
5.0 g/dscm (assuming 99 percent removal efficiency).
---------------------------------------------------------------------------
\59\ To achieve a standard of 50 g/dscm 99 percent of
the time, a source with average emissions variability must be
designed and operated to achieve an emission level of 30 g/
dscm.
---------------------------------------------------------------------------
We note that another option for identifying BTF levels would be to
consider the CI or CB system as an add on to the floor controls
identified above. Under this option, emission levels prior to CI would
be assumed to be the floor level, 130 g/dscm. Thus, a CI
system at 90 percent removal could be expected to achieve a standard of
approximately 13 g/dscm. A CB system at 99 percent removal
could be expected to achieve a standard of approximately 1.3
g/dscm. We specifically request comment on whether this
approach of applying BTF reductions to the floor levels is appropriate.
We also note that an alternative approach to using a statistically-
derived variability factor to account for emissions variability would
be to assume a conservative control efficiency for the CI or CB BTF
technology. We believe that using a conservative removal efficiency
could adequately account for emissions variability. Under this
approach, we would conservatively assume that CI-controlled systems
could achieve a removal efficiency of 80 percent and that CB-controlled
systems could achieve an efficiency of 90 percent. When these removal
efficiencies are applied to the floor level of 130 g/dscm
(corresponding to a design level of 57 g/dscm), this would
result in emission standards of 11 g/dscm for CI-controlled
systems, and 5.7 g/dscm for CB-controlled systems.60 We
invite comment on this alternative approach to account for emissions
variability among runs within a test condition.
---------------------------------------------------------------------------
\60\ The same approach could be applied to the previously
discussed approach of applying the BTF control to an assumed
emission level of 300 g/dscm. When assuming the
conservative removal efficiencies of 80 percent for CI and 90
percent for CB, this would result in BTF standards of 60 g/
dscm for CI-controlled systems and 30 g/dscm for CB-
controlled systems. A statistically-derived variability factor would
not be added because emissions variability is accounted for by
assuming conservative (i.e., lower-than-expected) removal
efficiencies for CI and CB systems.
---------------------------------------------------------------------------
For the reasons discussed below, EPA believes that a BTF level
based on use of CI is warranted and is proposing a MACT standard of 50
g/dscm. The proposed standard would result in nationwide Hg
emissions reductions of 757 lbs per year above the floor level and
7,922 lbs per year from baseline levels, and the incremental annualized
cost to achieve the BTF level over the floor level would be $7.7
million.
EPA has considered costs in relation to emissions reductions and
the special bioaccumulation potential that Hg poses and determined that
proposing a BTF limit is warranted. Hg is one of the more toxic metals
known due to its bioaccumulation potential and the adverse neurological
health effects at low concentrations especially to the most sensitive
populations at risk (i.e., unborn children, infants and young
children). Congress has singled out mercury in CAA section 112(c)(6)
for prioritized control. A more detailed discussion of human health
benefits for mercury can be found in Part Seven of today's proposal.
The chief means of control, activated carbon injection, also controls
D/F so that there are distinct efficiencies in control.61
---------------------------------------------------------------------------
\61\ As discussed for D/F, we invite comment on whether the
final rule should establish floor levels, rather than BTF levels,
for Hg for small incinerators. This is because the Agency is
concerned about the cost-effectiveness of the BTF levels for small
incinerators.
---------------------------------------------------------------------------
The Agency evaluated a more stringent standard of 8 g/dscm
for Hg emissions based on CB technology. This standard would result in
additional national Hg reductions of 960 lbs per year over the proposed
standard of 50
[[Page 17385]]
g/dscm at an incremental annualized national cost of $20
million. The Agency does not believe that a CB-based emission level of
8 g/dscm would be appropriate.
4. Semivolatile Metals (SVM) (Cadmium and Lead)
a. MACT Floor. Emissions of SVMs from HWIs are currently controlled
by PM control devices. In addition, some incinerators have specific
emission limits for these metals established under RCRA omnibus permit
authority. The Agency has a database for SVM emissions from 42 HWIs,
which indicates a range (by test condition average) from a low of 1.46
to a high of 29,800 g/dscm. For the MACT analysis, the median
of the best performing 12 percent of HWIs were found to be using: (1) a
venturi-scrubber (VS) 62 with a MTEC level of 170 g/dscm;
(2) a combination of ESP and WS with a MTEC level of 5,800 g/
dscm; and (3) a combination of VS and IWS with a MTEC of 49,000
g/dscm.63 Accordingly, we identified these technologies
as MACT floor.
---------------------------------------------------------------------------
\62\ Because virtually all other PM control devices (e.g., ESP,
FF, IWS) would be expected to have a SVM collection efficiency
equivalent to or better than a VS, a source equipped with any PM
control device and having a MTEC less than 170 g/dscm was
considered to be using MACT floor control.
\63\ We considered a FF to have equivalent (or better) SVM
removal efficiency compared to an IWS. Thus, we considered a source
equipped with a FF and any wet scrubber (ahead of the FF) and having
a MTEC less than 49,000 g/dscm to be using MACT floor
control. A FF alone may not provide equivalent control of SVM
because SVM can be volatile in stack emissions.
---------------------------------------------------------------------------
To identify an emission level that these technologies could
routinely achieve, we evaluated the emission levels from all HWIs
equipped with these controls.64 We identified the test condition
in this expanded MACT pool with the highest average emission and used
procedures discussed above in Part Three, Section V, (i.e., addition of
a within-test condition emissions variability factor to the log mean of
the runs for this test condition) to identify a MACT floor level 270
g/dscm.
---------------------------------------------------------------------------
\64\ Sources with better controls (MACT technology and lower
feedrate expressed as MTEC) were also included in the expanded MACT
pool.
---------------------------------------------------------------------------
We estimate that approximately 65 percent of all incinerators
currently meet this MACT floor level. Sources not already meeting the
floor level can readily achieve it by making design, operation, or
maintenance improvements to their existing PM control system or by
retrofitting with a new PM control device.
The national annualized cost to HWIs to comply with the proposed
floor level is estimated to be $9.9 million, and would provide a
reduction in Cd and Pb emissions of 50 tons/year, a 94 percent
reduction in emissions.
b. Beyond-the-Floor Considerations. The Agency is not proposing a
more stringent BTF standard for SVM. We note that the floor level alone
would provide for a 94 percent reduction in emissions, and emissions at
the floor are not likely to trigger the need for additional control for
these sources under RCRA.
5. Low Volatile Metals (Arsenic, Beryllium, Chromium and Antimony)
a. MACT floor. The Agency has a database for LVM emissions from 41
HWIs, which indicates a range (by test condition average) from a low of
3.5 to a high of 133,000 g/dscm. For MACT analysis, the median
of the best performing 12 percent of HWIs achieved the LVM emission
levels using: (1) a venturi-scrubber (VS) for MTECs up to 1,000
g/dscm; and (2) an ionizing wet scrubber (IWS) for MTECs up to
6,200 g/dscm. Accordingly, we identified these technologies as
MACT floor.
In addition, we consider any PM control device to provide
equivalent LVM control to a VS. We therefore identified an ESP, IWS, or
FF with a MTEC up to 1,000 g/dscm as MACT floor control.
Similarly, we consider a FF or ESP as equivalent technology to a IWS.
Thus, a FF or ESP coupled with a MTEC up to 6,200 g/dscm is
also considered MACT floor control.
To identify an emission level that these technologies could
routinely achieve, we considered the emissions from all HWIs in our
database equipped with MACT floor control. We identified the test
condition in this expanded MACT pool with the highest average emissions
and added a within-test condition emissions variability factor to the
log-mean of the test condition runs. See Part Three, Section V, above.
Accordingly, we have identified a MACT floor level of 210 g/
dscm.
Approximately 80 percent of all test conditions in our database
achieved the MACT floor level even though many HWIs were equipped with
different APCDs or had higher MTECs. EPA believes that most HWIs would
be able to achieve the proposed MACT floor without installing an add-on
control system. The control technologies necessary to achieve the MACT
floor level are already being used by many HWIs for PM and acid gas
control.
The national annualized cost to HWIs to comply with the floor level
would be $7.7 million and would provide an incremental reduction in LVM
emissions of 25 tons/year (91 percent) from the baseline emissions
level of 27.3 tons/year.
b. Beyond-the-Floor Considerations. The Agency is not proposing a
more stringent LVM standard using BTF controls (i.e., better performing
PM control equipment). We note that the floor level alone would provide
for a 91 percent reduction in emissions, and emissions at the floor are
not likely to trigger the need for additional control for these sources
under RCRA.
6. Hydrochloric Acid and Chlorine
a. MACT floor for HCl/Cl2. The Agency's database for HCl/
Cl2 emissions from 59 HWIs indicates a range (by test condition
average) from a low of 0.1 to a high of 1068 ppmv (expressed as HCl
equivalents). For MACT analysis, the median of the best performing 12
percent of HWIs achieving the lowest HCl/Cl2 emission levels were
found to be using some kind of scrubbing using combinations of
absorber, ionizing wet scrubber, VS, packed bed scrubber (PBS), or
generic wet scrubber. In addition, the best performing sources had a
chlorine feedrate of up to 2.1E7 g/dscm, expressed as a MTEC.
Accordingly, we identified MACT floor control as wet scrubbing coupled
with a chlorine MTEC up to 2.1E7 g/dscm.
To identify an emission level that wet scrubbing with an MTEC up to
2.1E7 g/dscm could routinely achieve, we considered the
emissions from all HWIs in our database equipped with these controls.
We identified the test condition in this expanded MACT pool with the
highest average emissions and added a within-test condition emissions
variability factor to the log-mean of the test condition runs. See Part
Three, Section V, above. Accordingly, we have identified a MACT floor
level of 280 ppmv.
Over 90 percent of all test conditions in our database achieve this
MACT floor level. At current baseline levels, HWIs emit 1712 tons/year
of HCl/Cl2, and at today's proposed MACT standard, these emissions
would be reduced by 592 tons/year, a reduction of 35 percent. The
estimated annualized national cost to the industry to meet the proposed
MACT standard would be $4.5 million.
b. Beyond the-Floor Considerations. The Agency considered whether
to propose a BTF level and determined that it would not be warranted.
We note that emissions at the floor are not likely to trigger the need
for additional control for these sources under RCRA.
7. Carbon Monoxide and Hydrocarbons
As discussed in Section I above, the Agency believes that
establishing emission limits and continuous
[[Page 17386]]
monitoring of two surrogate compounds (hydrocarbons (HC) and carbon
monoxide (CO)) will help control emissions of non-dioxin organic HAPs
(in combination with PM control to control absorbed organic HAPs).
a. MACT Floor for HC. The Agency's database for HC emissions from
31 HWIs indicates a range (by test condition average) from a low of 0.2
to a high of 35.8 ppmv. Unlike certain cement kilns and LWAKs,
incinerators are not required to monitor HC under RCRA regulations.
Facilities generally obtained HC emissions data for their own
information and often used an unheated FID detector, in which soluble
volatiles and semivolatiles are condensed out before entering the
detector. Also much of the data were based on run averages (as opposed
to the maximum hourly rolling average format proposed today).65
Notwithstanding these shortcomings, the Agency used these data to
identify a MACT floor level.
---------------------------------------------------------------------------
\65\ The average of emissions over a run is lower than the
maximum hourly rolling average for the run. In addition, unheated
FIDs report lower HC levels than a heated FID that would be required
under today's proposal. Both of these factors would lead the Agency
to underestimate the cost of compliance. On the other hand, the HC
levels in the database were measured during worst-case, trial burn
conditions. Thus, these emissions are likely to be much higher than
during normal operations. This factor has lead the Agency to
overestimate compliance costs.
---------------------------------------------------------------------------
The Agency identified MACT control for HC as operating under good
combustion practices (GCPs). GCPs include techniques such as thorough
air, fuel, and waste mixing, provision of adequate excess oxygen,
maintenance of high temperatures to destroy organics, design of the
facility to provide high enough residence times for destruction of
organics, operation of the facility by qualified and certified
operators, and periodic equipment maintenance to manufacturer-
recommended standards.
To identify the MACT floor level, the Agency conducted a
quantitative evaluation of the data combined with engineering judgment
to identify test conditions that appear to be conducted under good
combustion conditions. Since it is not possible to say with certainty
which test conditions were conducted using GCPs absent a detailed
examination of all test conditions, we conducted the analysis by
arraying the entire HC database from the lowest to the highest emission
levels. We then assumed that test conditions beyond a clear break-point
were not operated under GCPs. Based on the above analysis and a
statistical evaluation of the level that the average source can achieve
99 percent of the time, the Agency identified a MACT floor level of 12
ppmv.
We estimate that the annualized burden on HWIs to meet this floor
level would be $8.5 million. An annual reduction of 49 tons of HC
emissions (20 percent) is expected from the baseline levels of 239
tons/year.
EPA specifically invites comment on the approach used to identify
the MACT floor level and requests HC data on a hourly rolling average
basis, using heated FID monitors.
b. MACT floor for CO. RCRA regulations for HWIs were promulgated in
1981 and limit CO emissions to levels achieved during the trial burn.
(As noted elsewhere, facilities typically design trial burns to
maximize CO in order to provide operational flexibility.) Most of our
database for CO (from 59 facilities) is based on run-averages during
trial burns (rather than an hourly rolling average-basis; see
discussion below). The CO levels in our database that are on a run-
average basis range from 0.3 to 10,400 ppmv.
We are proposing today a maximum hourly rolling average (MHRA)
format for CO (and HC), which is the same format in which a standard of
100 ppmv (Tier 1) was proposed in 1990 for HWIs (see 55 FR 17862 (April
7, 1990)) and promulgated for CKs and LWAKs in 1991 (see 56 FR 7134
(February 21, 1991)).
Although the Agency did not promulgate a final rule for CO
emissions from HWIs (because of Agency resource constraints), the
Agency published a guidance document 66 wherein a Tier 1 CO limit
of 100 ppmv HRA was recommended for control of PIC emissions if
warranted on a site-specific basis. Accordingly, subsequent trial burns
for HWIs have been conducted using a HRA format for CO. Our CO database
in the HRA format is comprised of 17 test conditions and has a range of
10 to 1,500 ppmv.
---------------------------------------------------------------------------
\66\ USEPA, ``Guidance on PIC Controls For Hazardous Waste
Incinerators'', April 1990, EPA/530-SW-90-040.
---------------------------------------------------------------------------
For MACT determination, the Agency conducted an analysis similar to
that described above for HC and a CO MACT floor level of 120 ppmv
resulted (e.g., MACT floor control is GCPs, and a break-point analysis
was used to identify sources likely to be truly using GCPs).
Nonetheless, since the Agency has previously proposed a CO limit of 100
ppmv and since this level is readily achievable by well-designed and
well-operated HWIs, the Agency is proposing 100 ppmv HRA as the MACT
floor.
We note that this floor level compares favorably with CO standards
for other types of incinerators such as medical waste incinerators for
which the proposed standard is 50 ppmv (60 FR 10654, February 27,
1995), and mass burn and fluidized bed municipal waste incinerators for
which the promulgated CO standard is 100 ppmv (60 FR 65382, December
19,1995).
The Agency estimates that at a 100 ppmv standard, national CO
emission reductions of 13,200 tons/year could be achieved from the
baseline level of 14,080 tons/year at an annualized national cost of
$17.4 million.
c. Beyond-the-Floor Considerations. The Agency considered more
stringent BTF limits for CO and HC. Although state-of-the-art HWIs
operating under GCPs should be able to routinely achieve levels below
100 ppmv HRA for CO and 12 ppmv HRA for HC, the Agency is concerned
that the incremental compliance cost may not warrant more stringent
standards.
EPA invites comments specifically on: (1) the use of CO and HC as
surrogates for non-dioxin organic emissions; and (2) data and
information and suggestions on an approach to identify a lower floor
level for HC that more accurately reflects the levels that are being
routinely achieved by HWIs operating under GCPs.
8. MACT Floor and BTF Cost Impacts
The annualized national cost to achieve the proposed standards is
estimated at $486,000 for each on-site incinerator unit and $731,000
for each commercial unit. The total (pre-tax) national annualized cost
is estimated to be $90 million for on-site and $25 million for
commercial incinerators. These costs include a CEMS cost of $130,000
per source annually. The most expensive HAPs would be dioxins and
mercury, for which BTF levels have been proposed, and would cost $3.0
million and $30 million respectively nationally at MACT floor levels,
and $29.2 million and $37.2 million respectively at BTF levels. These
costs include maintenance and operation of the equipment and CEMS. CEMS
account for 18 percent of the total compliance cost. Details of these
cost estimates have been provided in ``Second Addendum to the
Regulatory Impact Assessment for Proposed Hazardous Waste Combustion
Standards'' and are based on no market exit by any HWI and assuming
that the facilities have only a limited ability to pass through the
costs of the rule to generators.
The Agency, however, estimates that perhaps 4 of the 34 commercial
facility units and up to 51 of the 184 on-site facility units would
elect to cease
[[Page 17387]]
burning hazardous wastes as a result of today's proposals. Most of
these facilities burn small quantities of hazardous wastes. These
facilities would likely find it more economical to transport the
hazardous wastes to other facilities, while perhaps continuing to burn
other non-hazardous and industrial wastes, in lieu of incurring
expenditures to upgrade their units to continue to burn that small
quantity of HW under MACT standards. As such, the total quantity of
wastes burned would not be affected since those wastes would be burned
by other HWCs, for which there appears to be sufficient capacity
available.
B. Summary of MACT Standards For New Incinerators
1. Basis for MACT New
According to Section 112 of CAA, the degree of reduction in
emissions deemed achievable for new facilities may not be less
stringent than the emissions control achieved in practice by the best
controlled similar unit. This section summarizes EPA's rationale for
establishing MACT standards for new HWIs. The methodology for
determining the standards for new incinerators is similar to that for
existing sources, except that MACT floor control is based on the single
best performing technology, and the MACT pool is expanded to consider
emissions from any source using that technology. For more details see
``Draft Technical Support Document for HWC MACT Standards, Volume III:
Selection of Proposed MACT Standards and Technologies''.
The Agency is proposing the following standards for new HWIs:
Table IV.3.B.1--Proposed MACT Standards for New Incinerators
------------------------------------------------------------------------
HAP or HAP surrogate Proposed standard a
------------------------------------------------------------------------
Dioxins/furans......................... 0.2 ng/dscm TEQ.
Particulate matter..................... 69 mg/dscm (0.030 gr/dscf).
Mercury................................ 50 g/dscm.
SVM [Cd, Pb]........................... 62 g/dscm.
LVM [As, Be, Cr, Sb]................... 60 g/dscm.
HCl + Cl2.............................. 67 ppmv.
CO..................................... 100 ppmv.
HC..................................... 12 ppmv.
------------------------------------------------------------------------
a All emission levels are corrected to 7 percent O2.
2. MACT New for Dioxin/Furans
a. MACT New Floor. EPA examined its emissions database and
identified the single best performing existing source, and found that
the test condition with the lowest PCDD/F TEQ emissions had a test-
condition average of 0.005 ng/dscm. This facility employs a water
quench and wet scrubbing air pollution control systems (APCSs). The D/F
emission control by this source is being achieved by inhibiting the
formation of D/F in the APCD by rapid quench of the hot gases from the
combustion chamber. Therefore, the Agency selected wet scrubbing and
low APCD inlet temperature (400 deg. F) as the MACT floor control.
To determine an emission level that this the floor control could be
expected to achieve, the Agency considered data from all HWIs using the
MACT floor control. Using the same methodology as used for identifying
the floor level for existing sources, the Agency identified a MACT
floor level of 0.20 ng/dscm TEQ or an APCD inlet temperature of
400 deg. F.
b. Beyond-the-Floor (BTF) Considerations. As discussed above for
existing sources, the Agency selected activated carbon injection (ACI)
as the BTF technology. ACI is routinely effective in removing greater
than 95 percent of D/F from flue gases. The Agency had identified a BTF
level of 0.2 ng/dscm TEQ for the same reasons discussed above for the
BTF standard for existing sources.
The Agency also consider a carbon bed as a BTF technology to
achieve lower emission levels. As discussed for existing sources,
however, the Agency is concerned that the cost of carbon beds may not
be warranted given the incremental emissions reduction over a ACI-based
BTF standard.
3. PM Standard for New HWIs
The single best performing source in our database for PM emissions
was a source equipped with a FF having an air to cloth ratio of 3.8
acfm/ft \2\. Thus, this technology represents MACT new floor control.
When we considered emissions data from all sources equipped with this
level of control (or better), we identified a floor level of 0.039 gr/
dscf.
The Agency considered more efficient PM control (e.g., lower air-
to-cloth ratio, better bags) as BTF control that could achieve
alternative BTF levels of 0.03 or 0.015 gr/dscf. These are the same
controls investigated for BTF considerations for existing sources.
The Agency is proposing the same BTF standard for new sources as it
is proposing for existing sources--(69 mg/dscm or 0.03 gr/dscf). This
standard is readily achievable. The Agency is not proposing a 0.015 gr/
dscf standard because, as discussed for existing sources, it is not
clear that the additional cost is warranted considering the incremental
reduction in PM.
4. Mercury Standard for New HWIs
a. MACT New Floor. The single best performing source in our
database for Hg emissions was a source equipped with a wet scrubber
(WS) and having a MTEC of 51 g/dscm. The Agency considered any
wet scrubbing device an equivalent control technology (when coupled
with a MTEC up to 51 g/dscm) because of the ability to scrub
soluble forms of mercury species. Thus, the Agency identified MACT new
floor control as any wet scrubber coupled with a MTEC up to 51
g/dscm. When we considered emissions data from all sources
equipped with this level of control, we identified a floor level of 115
g/dscm.
b. Beyond-the-Floor Considerations. As for existing sources, the
Agency considered the use of both activated carbon injection (ACI) and
carbon bed (CB) as alternative BTF technologies. We are proposing a BTF
standard of 50 g/dscm for new sources based on use of ACI for
the same reasons we are proposing this standard for existing sources.
5. Semivolatile Metals Standard for New HWIs
a. MACT New Floor. The single best performing source in our
database for SVM emissions was a source equipped with a VS in
combination with a IWS, and having a MTEC of 49,000 g/dscm.
The Agency considered a wet scrubber in combination with a FF (coupled
with a MTEC up to 49,000 g/dscm) to provide equivalent or
better control of SVM. Thus, these technologies represent MACT new
floor control. When we considered emissions data from all sources
equipped with this level of control, we identified a floor level of 240
g/dscm.
b. Beyond-the-Floor Considerations. The Agency believes that state-
of-the-art FFs can achieve much lower emissions of SVM. For example,
the Agency has determined that MWCs equipped with a FF can achieve more
than a 99 percent reduction in SVM. See 59 FR 48198 (September 20,
1994). Given that we have identified a MACT new floor (design) level
for cement kilns of 35 g/dscm (see discussion in Section IV
below), we believe that a design level of 35 g/dscm for HWIs
is achievable, reasonable, and appropriate. To ensure that a source
that is designed to meet a SVM level of 35 g/dscm can meet the
standard 99 percent of the time (assuming the source has average
within-test condition emissions variability for sources equipped with
[[Page 17388]]
ESPs and FFs), the Agency has established a standard of 62 g/
dscm.
We note that SVM emissions at this level are not likely to result
in additional regulation of these sources to satisfy RCRA health risk
concerns.
6. Low Volatile Metals Standard for New HWIs
a. MACT New Floor. The single best performing source in our
database for LVM emissions was a source equipped with a VS with an MTEC
of 1,000 g/dscm. Given the LVM collection efficiency of a VS,
the Agency considered any PM control device (e.g., ESP, IWS, FF) to
provide equivalent or better collection efficiency. Thus, these
technologies represent MACT new floor control. When we considered
emissions data from all sources equipped with this level of control, we
identified a floor level of 260 g/dscm. (We note that this
floor level for new sources is higher than the floor level proposed for
existing sources. Although the statistically-derived emissions
variability factor was added to the same test condition for both MACT
existing floor and MACT new floor, the variability factor was greater
for test conditions in the MACT new expanded pool.)
b. Beyond-the-Floor Considerations. The Agency believes that state-
of-the-art PM control devices (e.g., ESPs, IWS, FFs) can achieve LVM
emission levels well below the floor level. Given that we have
identified a floor (design) level 67 for new CKs and new LWAKs of
35 g/dscm and 26 g/dscm, respectively (see discussion
in Sections IV and V below), we believe that a BTF design level of 35
g/dscm is achievable, reasonable, and appropriate for new
HWIs. To ensure that a source that is designed to meet a LVM level of
35 g/dscm can meet the standard 99 percent of the time
(assuming the source has average within-test condition emissions
variability for sources equipped with ESPs and FFs), the Agency has
established a standard of 60 g/dscm.
---------------------------------------------------------------------------
\67\ That is, the log mean of runs for the test condition in the
expanded MACT pool with the highest average emission. A within-test
condition emissions variability factor (based on test conditions in
the expanded MACT pool) is added to the log-mean for this test
condition to derive the standard.
---------------------------------------------------------------------------
We note that LVM emissions at this level are not likely to result
in additional regulation of these sources to satisfy RCRA health risk
concerns.
As discussed elsewhere in today's proposal, we are encouraging but
not requiring sources to document compliance with the metals standard
using a multi-metal continuous monitoring system (CEMS). Given that
available information indicates that a multi-metal CEMS could not
effectively detect LVM emissions below 80 g/dscm, we are
proposing an alternative standard of 80 g/dscm for sources
that elect to document compliance with a CEMS.
7. HCl and Cl2 Standards for New HWIs
a. MACT New Floor. The single best performing source in our
database for HCl and Cl2 emissions was a source equipped with a
wet scrubber with a MTEC of 1.7E7 g/dscm. The Agency
considered any wet scrubber to be equivalent technology. Thus, MACT new
floor control is defined as wet scrubbing with a MTEC up to 1.7E7
g/dscm. When we considered emissions data from all sources
equipped with this level of control, we identified a floor level of 280
ppmv.
b. Beyond-the-Floor Considerations. The Agency believes that state-
of-the-art wet scrubbers can readily achieve better than 99 percent
removal of HCl and Cl2. Applying this removal efficiency to the
test condition in our database with the highest average emission (i.e.,
1,100 ppmv; no emission control device) results in an emission of 11
ppmv. We do not believe, however, that it is necessary to establish a
BTF (design) level 68 this low for HCl and Cl2. Accordingly,
we believe that it is reasonable and appropriate to establish a design
level of 25 ppmv which corresponds to a statistically-derived standard
of 67 ppmv.69
---------------------------------------------------------------------------
\68\ An emissions variability factor would be added to the log-
mean of the runs of this test condition to derive a standard.
\69\ The variability factor is based on within-test condition
emissions variability for incinerators equipped with wet scrubbers.
---------------------------------------------------------------------------
We note that this level is consistent with the levels we are
proposing for new CKs (67 ppmv BTF level) and new LWAKs (62 ppmv floor
level). Further, we note that HCl and Cl2 emissions at this level
are not likely to result in additional regulation of these sources to
satisfy RCRA health risk concerns.
8. Carbon Monoxide and Hydrocarbon Standards for New HWIs
As with existing sources, CO and HC in conjunction with PM remain
the parameters of choice to monitor continuously for controlling non-
dioxin organics. Current regulations require continuous monitoring of
CO, but not of HC, and so the database of CO from incinerators is quite
extensive. However, the format of our CO data is mostly on a run
average basis as explained above. The CO levels of the best performing
facility in this database are less than 10 ppmv hourly rolling average
(HRA). The technology to achieve low level of non-dioxin organics is
``Good Combustion Practices'', which is the same as for existing
sources.
As such, we are proposing the same MACT standards for CO and HC as
for existing sources, but request comments on whether more stringent
standards would be more appropriate for new sources. The promulgated
standard for new large MWCs ranges from 50 to 150 ppmv based on type of
the device and the Agency would like to consider more stringent levels
for CO and HC that are representative of good combustion practices in
new HWIs in the final rule.
9. MACT New Cost Impacts
The annualized incremental costs (capital, operation and
maintenance) for a small, medium and large HWI based on today's
proposed control levels are estimated at $336K, $514K and $772K,
respectively. Major increases are due to installing FF, activated
carbon injection (for D/F and Hg control) and scrubbing devices (for
acid gas control). For this analysis, it was assumed that baseline
facilities can comply with existing regulations using a wet scrubber
and venturi-scrubber. Since the number of new facilities starting
construction every year is uncertain, total annualized incremental cost
for all the new HWIs in the U.S. due to today's proposal cannot be
estimated. The above costs include increased costs of APCS' needed
above baseline levels, and do not include costs of the main incinerator
system or the ancillary systems like fans, stack etc. Details of these
costs have been provided in the ``Regulatory Impact Assessment for the
Proposed Hazardous Waste Combustion MACT Standards''.
C. Evaluation of Protectiveness
In order to satisfy the Agency's mandate under the Resource
Conservation and Recovery Act to establish standards for facilities
that manage hazardous wastes and issue permits that are protective of
human health and the environment, the Agency conducted an analysis to
determine if the proposed MACT standards satisfy RCRA requirements, or
whether independent RCRA standards would be needed. These analyses were
designed to assess both the potential risks to individuals living near
hazardous waste combustion facilities who are highly exposed and risks
to other less exposed individuals living near such facilities. The
Agency evaluated potential risks both from direct inhalation exposures
and from indirect exposures through deposition onto soils and
vegetation and
[[Page 17389]]
subsequent uptake through the food chain. The Agency evaluated a
variety of exposure scenarios representing various populations of
interest, including subsistence farmers, subsistence fishers,
recreational anglers, and home gardeners.70 In characterizing the
risks within these populations of interest, both high-end and central
tendency exposures were considered.
---------------------------------------------------------------------------
\70\ In addition, the Agency evaluated a ``most exposed
individual'' for the purpose of assessing inhalation risks. A most
exposed individual (MEI) is operationally defined as an individual
who resides at the location of maximum predicted ambient air
concentration.
---------------------------------------------------------------------------
The primary exposure parameter considered in the high-end
characterization was exposure duration. For the baseline, 90th
percentile stack gas concentrations were also included in the high-end
characterization to reflect the variability in current emissions. For
dioxins at the floor, the high-end characterization also included 90th
percentile stack gas concentrations to reflect the large variation in
dioxin emissions using the floor technology (i.e., temperature
control). For the MACT standards, the Agency used the design value
which is the value the Agency expects a source would have to design in
order to be assured of meeting the standard on a daily basis and hence
is always a lower value than the actual standard for all HAPs
controlled by a variable control technology.71 The procedures used
in the Agency's risk analyses are discussed in detail in the background
document for today's proposal.72
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\71\ For the semi-volatile and low volatility metals categories,
the Agency assumed the source could emit up to the design value for
each metal in the category for the purpose of assessing
protectiveness.
\72\ ``Risk Assessment Support to the Development of Technical
Standards for Emissions from Combustion Units Burning Hazardous
Wastes: Background Information Document,'' February 20, 1996.
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The risk results for hazardous waste incinerators are summarized in
Table III.C.1 for cancer effects and Table III.C.2 for non-cancer
effects for the populations of greatest interest, namely subsistence
farmers, subsistence fishers, recreational anglers, and home gardeners.
The results are expressed as a range where the range represents the
variation in exposures across the example facilities (and example water
bodies for surface water pathways) for the high-end and central
tendency exposure characterizations across the exposure scenarios of
concern. For example, because dioxins bioaccumulate in both meat and
fish, the subsistence farmer and subsistence fisher scenarios are used
to determine the range.73
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\73\ For the semi-volatile and low volatility metals categories,
the inhalation MEI scenarios are also used. For hydrogen chloride
and chlorine (Cl2) only the inhalation MEI scenarios are used.
Table III.C.1.--Individual Cancer Risk Estimates for Incinerators \1\
----------------------------------------------------------------------------------------------------------------------------------------------
Dioxins Semi-volatile metals \2\ Low volatile metals \3\
----------------------------------------------------------------------------------------------------------------------------------------------
Existing Sources
----------------------------------------------------------------------------------------------------------------------------------------------
Baseline............................. 2E-9 to 9E-5......................... 4E-9 to 7E-7........................ 2E-10 to 4E-6
Floor................................ 3E-9 to 5E-5 \4\..................... 5E-8 to 5E-7........................ 5E-8 to 8E-6
BTF.................................. 3E-9 to 2E-6 \5\.....................
----------------------------------------------------------------------------------------------------------------------------------------------
New Sources
----------------------------------------------------------------------------------------------------------------------------------------------
Floor................................ 3E-9 to 5E-5 \4\..................... 5E-8 to 5E-7........................ 5E-8 to 8E-6
BTF.................................. 3E-9 to 2E-6 \5\.....................
CEM Option \6\....................... ..................................... 2E-8 to 2E-7........................ 4E-8 to 6E-6
----------------------------------------------------------------------------------------------------------------------------------------------
\1\ Lifetime excess cancer risk.
\2\ Carcinogenic metal: cadmium.
\3\ Carcinogenic metal: arsenic, beryllium, and chromium (VI).
\4\ Based on 20 ng/dscm TEQ, the highest level known to be emitted at the floor.
\5\ Based on 0.20 ng/dscm TEQ.
\6\ Based on SVM standard of 60 g/dscm and LVM standard of 80 g/dscm (applicable only if the source elects to document compliance
using a multi-metals CEM).
Table III.C.2.--Individual Non-Cancer Risk Estimates for Incinerators \1\
----------------------------------------------------------------------------------------------------------------------------------------------
Semi-volatile metals \2\ Low volatile metals \3\ Hydrogen chloride Chlorine
----------------------------------------------------------------------------------------------------------------------------------------------
Existing Sources
----------------------------------------------------------------------------------------------------------------------------------------------
Baseline..................... <0.001 to 0.02............... <0.001 to 0.2................ 0.001 to 0.05................ 0.008 to 0.7
Floor........................ <0.001 to 0.01............... <0.001 to 0.09............... 0.02 to 0.05 \4\............. 0.07 to 0.3 \5\
New Sources
----------------------------------------------------------------------------------------------------------------------------------------------
Floor........................ <0.001 to 0.01............... <0.001 to 0.09............... 0.02 to 0.05 \4\............. 0.07 to 0.3 \5\
BTF.......................... <0.001 to 0.003.............. <0.001 to 0.03............... 0.004 to 0.01 \4\............ 0.02 to 0.07 \5\
CEM Option \6\............... <0.001 to 0.004.............. <0.001 to 0.06...............
----------------------------------------------------------------------------------------------------------------------------------------------
\1\ Hazard quotient.
\2\ Cadmium and lead.
\3\ Antimony, arsenic, beryllium, and chromium.
\4\ HCl+Cl 2 assuming 100 percent HCl.
\5\ HCl+Cl 2 assuming 10 percent Cl 2.
\6\ Based on SVM standard of 60 g/dscm and LVM standard of 80 g/dscm (applicable only if the source elects to document compliance
using a multi-metals CEM).
[[Page 17390]]
The risk analysis indicates that for the semi-volatile and low
volatility metals category, the MACT standards for incinerators are
protective at the floor for both existing and new sources. The analysis
indicates that the CEM compliance option for new sources is also
protective. For hydrogen chloride and chlorine (Cl2), the MACT
standards for incinerators are also protective at the floor for both
existing and new sources. However, the analysis indicates that for
dioxins the proposed beyond the floor standards, rather than the floor
levels, are protective.
IV. Cement Kilns: Basis and Level for the Proposed NESHAP Standards for
New and Existing Sources
Today's proposal would establish new emission standards for
dioxins/furans, mercury, semivolatile metals (cadmium and lead), low
volatile metals (arsenic, beryllium, chromium and antimony),
particulate matter, acid gas emissions (hydrochloric acid and
chlorine), particulate matter (PM), hydrocarbons, and carbon monoxide
(for the by-pass duct) from existing and new hazardous waste-burning
cement kilns. See proposed Sec. 63.1204. The following discussion
addresses how MACT floor and beyond-the-floor (BTF) levels were
established for each HAP, and EPA's rationale for the proposed
standards. The Agency's overall methodology for MACT determinations has
been discussed in Part Three, Sections V and VI for existing sources
and in Section VII for new sources.
To conduct the MACT floor analyses presented today, the Agency
compiled all available emissions data from hazardous waste-burning
cement kilns. As noted earlier, the vast majority of this database is
comprised of compliance test emissions data generated as a result of
Boiler and Industrial Furnace (BIF) rule requirements.74 The
Agency is also aware that additional emissions data will become
available. Sources of new data include test reports generated from
compliance recertification testing (required every three years under
the BIF rule for interim status facilities; see Sec. 266.103(d)),
results from voluntary industry initiatives and testing programs,
supplemental emissions testing conducted by individual companies, and
data from pilot-scale research by EPA's Office of Research and
Development. As timely and appropriate, notice of these additional
data, if used as a basis for standards in this rulemaking, will be
published to allow for review. However, we emphasize again that, for
purposes of setting MACT standards, it is preferable to have data that
reflect the normal, day-to-day operations and emissions. In addition,
the Agency believes that this type of data will substantially assist in
the appropriate resolution of some of the issues (e.g., variability,
proper identification of sources in MACT floor pools, raw material feed
contributions to emissions) that are raised in the following sections.
We invite commenters to submit this type of data and to discuss these
issues in their comments.
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\74\ By August 21, 1992, or by the applicable date allowed by an
extension by the Regional Administrator, owners and operators of BIF
facilities burning hazardous waste were required to conduct
compliance testing and submit a certification of compliance with the
emissions standards for individual toxic metals, HCl, Cl 2,
particulate matter, and CO, and where applicable, HC and dioxin/
furans. See 40 CFR Sec. 266.103(c).
---------------------------------------------------------------------------
In addition, the Agency requests comments on whether we should use
emissions data from cement kilns that no longer burn hazardous waste
for MACT floor determinations.75 Even though these cement kilns
subsequently decided to stop burning waste, we believe that their
emissions data represent the level of emission control achieved at a
kiln burning hazardous waste and are therefore appropriate for use in a
MACT analysis. Moreover, the air pollution control equipment employed
by these facilities is similar in type, design and operation to
equipment employed by the waste-burning industry as a whole.
---------------------------------------------------------------------------
\75\ Cement kilns no longer burning hazardous waste include
three Southdown plants (Fairborn, OH, Knoxville, TN, and Kosmosdale,
KY) and North Texas Cement (Midlothian, TX).
---------------------------------------------------------------------------
The Agency conducted a preliminary analysis of the effect on MACT
floor levels of removing these emissions data from consideration, and
found no significant impacts (see discussion later in this section on
MACT floor levels) other than for semivolatile metals and hydrocarbons
in the by-pass duct. The SVM floor would rise from 57 g/dscm
(today's proposed floor level) to approximately 1200 g/
dscm.76 This level is much higher than the cement industry can
achieve.77 Also, the Agency notes that a SVM floor of 1200
g/dscm may necessitate the need to consider adopting further
controls under RCRA to address potential risks that SVMs (especially
cadmium) may pose.78
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\76\ The Agency notes that we are also taking comment on a SVM
floor level of 160 g/dscm (using an alternative approach
discussed later in this section). A SVM floor level of 1200
g/dscm appears unnecessarily high considering our proposed
floor analysis and that of others (e.g., see Part Four, section 9).
\77\ See letter from Craig Campbell, CKRC, to James Berlow, EPA,
undated but received February 20, 1996. We note that, although the
Agency is proposing a SVM standard of 57 g/dscm, we invite
comment on an alternative (and potentially preferable) approach to
identify MACT floor technology which would result in a floor-based
standard of 160 g/dscm. See discussion on SVM floor later
in this section. Because we identified the alternative approach late
in the rule development process, we are inviting comment on the
higher standard rather than proposing it.
\78\ The Agency doubts that a MACT beyond-the-floor level would
be warranted.
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In addition, the by-pass duct HC floor would be affected because
two-thirds of the HC data available to the Agency were generated by
these cement plants and would no longer be considered in the analysis.
This may make calculation of the HC MACT floor problematic using the
current MACT approach due to the limited remaining emissions data. The
remainder of the HAP floors would remain roughly at today's proposed
levels.
If EPA were to decide to exclude data from cement kilns that no
longer burn hazardous waste, the Agency then believes that emission
data from cement kilns that have made significant modifications or
retrofits to their manufacturing process (e.g., replacing a raw
material with one with different characteristics, installing new
control equipment) since the earlier emissions data were generated must
also be considered for exclusion from MACT analysis. The Agency
requests comment on whether we should use these emissions data (i.e.,
the data generated prior to significant process changes) in MACT
analysis. The commenter should also address how the Agency could
identify cement kilns that have made significant process changes and
the scope of modifications or retrofits that would significantly impact
emissions. Finally, since changes can affect some HAP emissions and not
others, the commenter should address whether this issue should be
decided on an individual HAP basis.
A. Summary of Standards for Existing Cement Kilns
This section summarizes EPA's rationale for identifying MACT for
existing cement kilns that burn hazardous waste and the proposed
emission limits. The discussion of MACT includes discussions of
``floor'' controls and considerations of ``beyond-the-floor'' controls.
Table IV.4.A.1 summarizes the proposed emission limits.
[[Page 17391]]
Table IV.4.A.1.--Proposed Emission Standards for Existing Cement Kilns
------------------------------------------------------------------------
HAP or HAP surrogate Proposed standard a
------------------------------------------------------------------------
Dioxin/furans (TEQ)....................... 0.20 ng/dscm (TEQ).
Particulate Matter........................ 69 mg/dscm (0.030 gr/dscf).
Mercury................................... 50 g/dscm.
SVM (Cd, Pb).............................. 57 g/dscm.
LVM (As, Be, Cr, Sb)...................... 130 g/dscm.
HCl+Cl 2 (total chlorides)................ 630 ppmv.
Hydro-carbons:
Main Stack b............................ 20 ppmv.
By-pass Stack c......................... 6.7 ppmv.
Carbon Monoxide:
Main Stack.............................. N/A.
By-pass Stack c......................... 100 ppmv.
------------------------------------------------------------------------
a All emission levels are corrected to 7 percent O2.
b Applicable only to long wet and dry process cement kilns (i.e., not
applicable to preheater and/or precalciner kilns).
c Emissions standard applicable only for cement kilns configured with a
by-pass duct (typically preheater and/or precalciner kilns). Source
must comply with either the HC or CO standard in the by-pass duct. A
long wet or long dry process cement kiln that has a by-pass duct has
the option of meeting either the HC level in the main stack or the HC
or CO limit in the by-pass duct.
1. Dioxin/Furans
a. MACT Floor. The Agency's analysis of dioxin/furan (D/F)
emissions from HWCs and other combustion devices (e.g., municipal waste
combustors and medical waste incinerators) indicates that temperature
of flue gas at the inlet of the PM control device can have a major
effect on D/F emissions.79 D/F emissions generally decrease as the
gas temperature of the PM control device decreases, and emissions are
lowest when the gas temperature of the PM control device are below the
optimum temperature window for D/F formation--450 deg.F to 650
deg.F.80 Given that CKs operate their ESPs and FFs under a range
of temperatures (i.e., from 350 deg.F to nearly 750 deg.F), the
Agency is identifying MACT floor for D/F based on temperature control
at the inlet to the ESP or FF.81
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\79\ USEPA, ``Draft Technical Support Document For HWC MACT
Standards, Volume III: Selection of Proposed MACT Standards and
Technologies'', February 1996.
\80\ For example, consider kiln #1 at the Ash Grove Cement
Company in Chanute, Kansas. During BIF certification of compliance
testing in 1992, Ash Grove dioxins/furans emissions exceeded 1.7 ng/
dscm (TEQ) at a control device temperature of 435 deg.F. Testing in
1994 at a temperature of approximately 375 deg.F resulted in
emissions less than 0.05 ng/dscm (TEQ).
\81\ The Agency notes, however, that other factors can affect D/
F emissions including presence of precursors in the feed or as a
result of incomplete combustion and presence of compounds thought to
inhibit surface-catalyzed formation of D/F such as sulfur. Thus, D/F
emissions may be low (e.g., 0.2 ng TEQ per dcsm) even though the
temperature of stack gas at the inlet to the ESP or FF may exceed
400-450 deg.F, and D/F emissions may be relatively high (e.g., 0.3-
0.5 ng TEQ per dscm) even though the temperature may be below that
range.
---------------------------------------------------------------------------
The emissions data for CKs includes results from 58 test conditions
collected from 19 cement plants, with a total of 28 kilns being tested.
The Agency's database shows that the average test condition D/F
emissions ranged from 0.004 to nearly 50 ng/dscm (TEQ).
Kilns emitting D/F at or below levels emitted by the median of the
best performing 12 percent of kilns had flue gas temperatures at or
below 418 deg.F at the inlet to the ESP or FF, while inlet temperatures
for other kilns ranged to nearly 750 deg.F. The Agency then evaluated
D/F emissions from all kilns that operated the ESP or FF at 418 deg.F
or less and determined that 75 percent had D/F emissions less than 0.2
ng/dscm (TEQ). The other 25 percent of kilns generally had TEQs less
than 0.8 ng/dscm (TEQ), although one kiln emitted 4.7 ng/dscm (TEQ).
The Agency is, therefore, identifying temperature control at the
inlet to the ESP or FF at 418 deg.F as the MACT floor control. Given
that 75 percent of sources achieve D/F emissions of 0.20 ng/dscm (TEQ)
at that temperature, the Agency believes that it is appropriate to
express the floor as ``0.20 ng/dscm (TEQ), or (temperature at the inlet
to the ESP or FF not to exceed) 418 deg.F''. This would allow sources
that operate at temperatures above 418 deg.F but that achieve the same
D/F emissions as the majority of sources that operate below 418 deg.F
(i.e., 0.20 ng/dscm (TEQ)) to meet the standard without incurring the
expense of lowering the temperature at the ESP or FF.
EPA estimates that over 50 percent of CKs currently are meeting the
floor level. The national annualized compliance cost 82 for CKs to
reduce D/F emissions to 0.20 ng/dscm (TEQ) or control ESP or FF inlet
temperature to below 418 deg.F would be $7.3 million for the entire
hazardous waste-burning cement industry, and would reduce D/F TEQ
emissions nationally by 830 grams/year (TEQ) or 96 percent from current
baseline emissions.
---------------------------------------------------------------------------
\82\ Total annual compliance costs are before consolidation and
do not incorporate market exit resulting from the proposed rule.
Also, CEM costs assume that no facilities currently have a HC
analyzer in place. Thus, these compliance costs may result in
overstated annual compliance costs. See the ``Second Addendum to the
Regulatory Impact Assessment for Proposed Hazardous Waste Combustion
MACT Standards'', February 1996, for details.
---------------------------------------------------------------------------
b. Beyond-the-Floor (BTF) Considerations. The Agency has identified
activated carbon injection (CI) at less than 400 deg.F as a BTF
control for D/F for cement kilns because CI is currently used in
similar applications such as hazardous waste incinerators, municipal
waste combustors, and medical waste incinerators. The Agency is not
aware of any CK flue gas conditions that would preclude the
applicability of CI or inhibit the performance of CI that has been
demonstrated for other waste combustion applications.
Carbon injection has been demonstrated to be routinely effective at
removing greater than 95 percent of D/F for MWCs and MWIs and some
tests have demonstrated a removal efficiency exceeding 99 percent at
gas temperatures of 400 deg.F or less.83 To determine a BTF
emission level, the Agency considered the emission levels that would be
expected to result from gas temperature control to less than 400 deg.F
combined with CI.
---------------------------------------------------------------------------
\83\ USEPA, ``Draft Technical Support Document for HWC MACT
Standards, Volume III: Selection of Proposed MACT Standards and
Technologies'', February 1996.
---------------------------------------------------------------------------
To estimate emissions with temperature control only, the Agency
considered the MACT floor database that indicates, as noted above, 25
percent of CKs operating the ESP or FF at temperatures above 418 deg.F
could be expected to emit D/F at levels above 0.2 ng/dscm (TEQ).
Although the majority could be expected to emit levels of 0.8 ng/dscm
(TEQ) or below, some could be expected to emit levels as high as 4.7 ng
TEQ.
When CI is used in conjunction with temperature control, an
additional 95 percent reduction in emissions could be expected.
Accordingly, emissions with these BTF controls could be expected to be
less than a range of 0.04 to 0.24 ng/dscm (TEQ) (i.e., 95 percent
reduction from 0.8 ng and 4.7 ng, respectively). Given that CI
reductions greater than 95 percent are readily feasible, the Agency
believes that it is appropriate to identify 0.20 ng/dscm (TEQ) as a
reasonable BTF level that could be routinely achieved.
The Agency notes that, because we have assumed a fairly
conservative carbon injection removal efficiency of 95 percent to
identify the 0.20 ng/dscm (TEQ) level, we believe that this approach
adequately accounts for emissions variability at an individual kiln
because CI removal efficiency is likely to be up to or greater than 99
percent. EPA thus believes that it is not necessary to add a
statistically-derived variability factor to the 0.20 ng/dscm (TEQ)
level to account for emissions variability at an individual kiln. Thus,
[[Page 17392]]
the 0.20 ng/dscm (TEQ) BTF level represents the proposed emission
standard.
EPA solicits comment on this approach, and notes that if a
statistically-derived variability factor were deemed appropriate with
the assumed conservative CI removal efficiency, the BTF level of 0.20
ng/dscm (TEQ) would be expressed as a standard of 0.31 ng/dscm (TEQ).
We note, however, that under this approach, it may be more appropriate
to use a less conservative, higher CI removal efficiency of 99 percent
(i.e., because emissions variability would be accounted for using
statistics rather than in the engineering decision to use a
conservative CI removal efficiency). Doing so would lower the 0.20 ng/
dscm (TEQ) level to approximately 0.04 ng/dscm (TEQ) (i.e., 99 percent
reduction from 0.8 ng and 4.7 ng results in levels of 0.008 ng to 0.047
ng/dscm (TEQ), respectively, and 0.04 ng is a reasonable value within
this range). If so, the D/F standard would be about 0.15 ng/dscm (TEQ)
(i.e., 0.04 ng/dscm TEQ plus the variability factor of 0.11 ng/dscm
TEQ).
We note that although CI is normally a relatively inexpensive
control technology to add to sources (with flue gas above the dew
point) that already have PM controls at the 69 mg/dscm level, CKs
present a special situation. This is because: (1) CI will remove Hg as
well as D/F (see discussion below regarding BTF control for Hg); (2)
CKs recycle as much collected PM as possible because it is useful raw
material and doing so reduces cement kiln dust (CKD) management cost;
(3) some CKs recycle the CKD by injecting it at the raw material feed
end of the kiln where the D/F may not be destroyed; and (4) to remove
Hg from the recycling system to ensure compliance with the Hg standard,
a portion of the CKD would have to be wasted.84
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\84\ We note that most CKs currently dispose of a portion of CKD
to control clinker quality (i.e., to control alkali salts).
Nonetheless, the economics of CKD management are uncertain at this
time given impending Agency action to ensure proper management.
Thus, we believe that CKs will increase efforts in the future to
minimize the amount of CKD that is disposed.
---------------------------------------------------------------------------
Accordingly, EPA has assumed that CKs that have to use CI to meet
the BTF standard (i.e., those that cannot achieve the standard with
temperature control alone) would install the CI system after the
existing ESP or FF and add a FF to remove the injected carbon with the
adsorbed D/F (and Hg). Although adding a new FF in series is an
expensive approach, it would enable CKs to meet both the proposed D/F
and Hg standards (as well as the PM, SVM, and LVM standards). Thus, the
cost of the CI and FF systems have been apportioned among these
proposed standards.
EPA estimates that 40 percent of CKs are currently meeting this BTF
level. The national incremental annualized compliance cost for the
remaining CKs to meet this BTF level 85 rather than comply with
the floor controls would be $6.6 million for the entire hazardous
waste-burning cement industry, and would provide an incremental
reduction in D/F (TEQ) emissions nationally beyond the MACT floor
controls of 20 grams/year (TEQ).
---------------------------------------------------------------------------
\85\ We note that not every source with D/F emissions currently
exceeding 0.20 ng TEQ per dscm would need to install CI to meet the
standard. As noted previously in the text, 75 percent of sources
could be expected to meet the standard with temperature control
only. In estimating the cost of compliance with the standard, EPA
considered the magnitude of current emissions and current operating
temperatures to project whether the source could comply with the
standard with temperature control only.
---------------------------------------------------------------------------
EPA has considered costs in relation to emissions reductions and
the special bioaccumulation potential that D/F pose and determined that
proposing a BTF limit is warranted.86 D/F are some of the most
toxic compounds known due to their bioaccumulation potential and wide
range of health effects at exceedingly low doses, including
carcinogenesis. Further, as discussed elsewhere in today's preamble,
EPA's risk analysis developed for purposes of RCRA shows that emissions
of these compounds from hazardous waste-burning cement kilns could pose
significant risks by indirect exposure pathways, and that these risks
would be reduced by BTF controls. Finally, EPA is authorized to
consider this non-air environmental benefit in determining whether to
adopt a BTF level. As noted earlier, exposure via these types of
indirect pathways was in fact a chief reason Congress singled out D/F
for priority MACT control in section 112(c)(6).
---------------------------------------------------------------------------
\86\ We note that the D/F BTF control technology, CI, would also
be used to control mercury emissions beyond the floor.
---------------------------------------------------------------------------
Finally, EPA's initial view is that it may need to adopt further
controls under RCRA to control D/F if it did not adopt the BTF MACT
standard. This would defeat one of the purposes of this proposal, to
avoid regulation of emissions under both statutes for these sources
wherever possible. These risks would, however, be reduced to acceptable
levels if emissions levels are reduced to 0.20 ng/dscm (TEQ).
For these reasons, the Agency is proposing a BTF level of 0.20 ng/
dscm (TEQ) for D/F emitted from hazardous waste-burning cement kilns.
2. Particulate Matter
a. MACT Floor. Cement kilns have high particulate inlet loadings to
the control device due to the nature of the cement manufacturing
process; that is, a significant portion of the finely pulverized raw
material fed to the kiln is entrained in the flue gas entering the
control device. CKs use ESPs or FFs to control PM to a 0.08 gr/dscf
standard under the BIF rule, unless the kiln is subject to the more
stringent New Source Performance Standard (NSPS) (see 40 CFR 60.60
(Subpart F)) of 0.3 lb/ton of raw material feed (dry basis) to the
kiln,87 which is generally equivalent to 69 mg/dscm or 0.03 gr/
dscf.
---------------------------------------------------------------------------
\87\ See Sec. 60.62 Standard for particulate matter for further
details.
---------------------------------------------------------------------------
The PM emissions data for CKs includes results from 54 test
conditions collected from 26 facilities, with a total of 34 units being
tested. The Agency analyzed all available PM emissions data and
determined that sources with emission levels at or below the level
emitted by the median of the best performing 12 percent of sources used
fabric filters with air-to-cloth (A/C) ratios of 2.3 acfm/ft\2\ or
less. Analysis of emissions data from all CKs using FFs with the 2.3
acfm/ft\2\ A/C ratio or less resulted in a level of 0.065 gr/dscf.
Because the NSPS is a federally enforceable limit that many cement
kilns are currently subject to, the Agency has chosen the existing NSPS
standard, not the statistically-derived limit discussed above, as MACT
for existing hazardous waste-burning CKs. Thus, the Agency is
identifying a MACT floor for PM and is identifying the floor level as
the NSPS limit of 69 mg/dscm (0.03 gr/dscf). Given that the NSPS
standard was promulgated in 1971, the Agency believes that it is
reasonable to consider it as the MACT floor level. We note further that
30 percent of cement kiln test conditions currently meet the 69 mg/dscm
floor level.
As mentioned above, the NSPS standard for PM is expressed as 0.3
lb/ton of raw material (dry basis) feed to the kiln. Although we are
proposing to establish the floor level as the MACT standard (see BTF
discussion below) expressed as 69 mg/dscm (0.03 gr/dscf), we
specifically invite comment on whether the standard should be expressed
in terms of raw material feed. We are proposing a ``mg/dscm'' basis for
the standard because a PM concentration in stack gas is commonly used
for waste combustors-hazardous waste incinerators, municipal waste
[[Page 17393]]
combustors, and medical waste incinerators. We note, however, that
using a ``mg/dscm'' basis for the CK standard would penalize the more
thermally efficient dry kilns (generally preheater and precalciner
kilns). This is because these kilns have lower stack gas flow rates per
ton of raw material feed because they do not need to provide additional
heat (by burning hazardous waste and/or fossil fuel) to evaporate the
water in the raw material slurry. Thus, wet kilns have higher gas flow
rates per ton of raw material than dry kilns because of increased
combustion gas and water vapor. This higher stack gas flow rate dilutes
the PM emissions and effectively makes a concentration-based standard
less stringent for wet kilns. Consequently, the Agency will consider
whether the final rule should express the floor standard as 0.3 lb/ton
of raw material (dry basis) feed to the kiln.
EPA estimates that 30 percent of cement kiln test conditions (in
our database) are currently meeting the floor level. The national
annualized compliance cost for the remaining CKs to reduce PM emissions
to the floor level would be $6.5 million for the entire hazardous
waste-burning cement industry, and would reduce PM emissions nationally
by 2400 tons per year.
b. Beyond-the-Floor Considerations. EPA considered but is not
proposing a more stringent beyond-the-floor level (e.g., 35 mg/dscm
(0.015 gr/dscf)) for cement kilns. For this analysis, EPA determined
that it does not have adequate data to ensure that, given the high
inlet grain loading caused by entrained raw material, CKs can routinely
achieve that emission level day-in and day-out with a single PM control
device--ESP or FF. We note that, to ensure compliance with a 35 mg/dscm
standard 99 percent of the time, a source with average emissions
variability must be designed and operated to achieve an emission level
of approximately 18 mg/dscm (or 0.008 gr/dscf). EPA estimates that 15
percent of CKs currently have average PM emissions below 18 mg/dscm.
Reducing the floor level from 69 mg/dscm to a BTF level of 35 mg/
dscm would require an improved technology such as the use of more
expensive fabric filter bags (e.g., bags backed with a teflon membrane)
or the addition of a FF for kilns with ESPs. The addition or upgrade of
FFs to all kilns could potentially be cost effective, since to meet the
proposed floor for SVM and LVM, as well as the proposed BTF for D/Fs
and Hg, addition of a new FF is projected for a majority of the kilns
(about 80 percent). Thus, a PM BTF level of 18 mg/dscm may be the
incremental cost between a fabric filter with conventional fiberglass
bags and state-of-the-art membrane-type bags for those kilns currently
employing FFs; the addition of new FFs with membrane bags for those
kilns with ESPs; or new FFs with membrane bags for the remaining
facilities which are not projected to need upgrades to meet the floor
and proposed BTF levels.
At first glance it may seem cost effective, primarily since an
improved BTF PM level would lead to added benefits with reduced SVM,
LVM, and condensed organics emissions. However, the Agency is uncertain
how facilities will meet the proposed SVM, LVM, D/FS, and Hg levels.
For example, kilns could meet the mercury BTF level with feedrate
control or carbon injection without addition of a new FF (potentially
incurring the penalty of reduced or eliminated kiln dust recycle).
Additionally, CKs could meet the D/F BTF level with PM control device
temperature reduction instead of carbon injection with an add-on FF.
Finally, kilns could meet the SVM and LVM floor levels with feedrate
control.
Therefore, many of the kilns may not add new FFs to comply with
proposed floor (e.g., SVM, LVM) or proposed BTF levels (e.g., D/FS, Hg)
and EPA's estimated engineering cost to meet the floor has been
conservatively overstated. Thus, it may not be accurate to conclude
that the BTF for PM is close to the incremental cost between FF fabric
types. Under this circumstance, the incremental cost is more accurately
the cost of many new FF unit additions which the Agency believes would
not be cost effective. For these reasons the Agency believes it is not
appropriate to propose a BTF PM standard of 35 mg/dscm for existing
CKs. EPA specifically invites comment on whether the final rule should
establish a BTF standard for PM of 35 mg/dscm (or 0.15 lb/ton of raw
material (dry basis) feed into the kiln).
3. Mercury
a. MACT Floor. Mercury emissions from CKs are currently controlled
by the BIF rule, and CKs have elected to comply with the BIF standard
by limiting the feedrate of Hg in the hazardous waste feed.88
Thus, the MACT floor level is based on hazardous waste feed control.
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\88\ BIF Hg emission limits are implemented by establishing
limits, in part, on the maximum feed rate of Hg in total
feedstreams. Feedstream sources of mercury include hazardous waste,
Hg spiking during compliance testing, raw material, coal and other
fuels.
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Mercury emissions from cement kilns range from 3 g/dscm to
an estimated 600 g/dscm. The Agency has Hg emissions data from
42 test conditions collected from 21 cement plants, with a total of 28
kilns being tested. Since mercury is a volatile compound at the typical
operating temperatures of ESPs and baghouses, collection of mercury by
these control devices is highly variable (e.g., Hg removal efficiencies
ranged from zero to more than 90 percent). Most of the mercury exits
the kiln system as volatile stack emissions, with only a small fraction
partitioning to the clinker product or CKD.
To identify the floor level for hazardous waste feed control, the
Agency determined that sources with Hg emissions at or below the level
emitted by the median of the best performing 12 percent of sources had
normalized hazardous waste Hg feedrates, or MTECs, (i.e., maximum
theoretical emission rates 89) of 110 g/dscm or less.
Analysis of all existing cement kiln sources using this hazardous waste
feedrate control resulted in a MACT floor level of 130 g/dscm.
To meet this standard 99 percent of the time, EPA estimates that a
source with average emissions variability 90 must be designed and
operated to routinely achieve an emission level of 81 g/dscm.
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\89\ MTEC is the hazardous waste Hg feedrate divided by the gas
flow rate.
\90\ This represents the variability of emissions among runs
within a test condition included within the expanded MACT pool.
---------------------------------------------------------------------------
We note that raw materials and fossil fuels also contribute to
cement kiln Hg feedrates and emissions. Given that all sources must be
able to meet the floor level using the floor control, we investigated
whether all CKs could meet the floor level by only controlling
hazardous waste Hg feedrate to the MACT MTEC of 110 g/dscm. We
have determined that all CKs in the Hg emissions database, except for
one kiln with apparently anomalous data on mercury in raw material,
would be able to meet the floor level using floor control.91 The
one kiln reported substantially higher Hg feedrates in the raw material
than other kilns. We believe that this data may either be erroneous or
the kiln may have spiked Hg into the raw material during BIF compliance
testing. We specifically invite data and comment on the issue of normal
Hg content in raw material.
---------------------------------------------------------------------------
\91\ USEPA, ``Draft Technical Support Document for HWC MACT
Standards, Volume III: Selection of Proposed MACT Standards and
Technologies'', February 1996.
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EPA estimates that nearly 80 percent of CKs could currently comply
with the floor level. The total annualized compliance cost for the
remaining kilns
[[Page 17394]]
to reduce Hg emissions to the floor level is estimated to be up to $7.5
million for the entire cement industry, and would reduce Hg emissions
nationally by 7,200 lbs per year, or by 58 percent from baseline
emissions.
b. Beyond-the-Floor Considerations. The Agency has considered two
BTF control options for improved Hg control: flue gas temperature
reduction to 400 deg.F or less followed by either carbon injection (CI)
or carbon bed (CB). Either control option would be implemented in
conjunction with hazardous waste feedrate control of Hg. Due to the
uncertainty surrounding the actions that cement kilns will undertake in
achieving increased Hg control (i.e., with respect to reducing the Hg
content of the hazardous waste received at the kiln versus installing
the carbon injection technology to capture volatilized mercury without
reducing Hg content in the hazardous waste feed), the Agency assumed a
conservative emissions level attributable to feedrate control to which
the Agency applied the BTF control technology (i.e., 300 g/
dscm). EPA believes that CI systems can routinely achieve Hg emission
reductions of 80 to 90 percent or better 92 and that CB systems
can routinely achieve Hg emissions of 90 to 99 percent or
better.93
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\92\ Memorandum from Frank Behan, USEPA, to RCRA Docket.
Discussion of mercury removal efficiency with activated carbon
injection during an emissions test at a Lafarge Corporation cement
kiln. February 26, 1996.
\93\ USEPA, ``Draft Technical Support Document for HWC MACT
Standards, Volume III: Selection of Proposed MACT Standards and
Technologies'', February 1996.
---------------------------------------------------------------------------
The BTF level under the CI-controlled option would, therefore, be
50 g/dscm (corresponding to a design level of 30 g/
dscm), based on 90 percent reduction after the source has controlled
its Hg emissions to 300 g/dscm by limiting Hg in the hazardous
waste. As discussed later, EPA is proposing a 50 g/dscm based
on this BTF option.\94\
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\94\ To achieve a standard of 50 g/dscm 99 percent of
the time, a source with average emissions variability must be
designed and operated to achieve an emission level of 30 g/
dscm.
---------------------------------------------------------------------------
The BTF level under the CB-controlled option would be 8 g/
dscm (corresponding to a design level of 5 g/dscm), based on
99 percent reduction after the source has controlled its Hg emissions
to 300 g/dscm by limiting Hg in the hazardous waste.
We note that another control option for identifying BTF levels
would be to consider the floor hazardous waste feedrate control--MTEC
of 110 g/dscm or less--an initial component of BTF control
followed by either CI or CB. Under this approach, BTF emission levels
would be identified by first assuming sources would impose only
feedrate controls to meet the floor level of 130 g/dscm
(corresponding to a design level of 81 g/dscm). Thus, a CI
injection system at 90 percent removal could be expected to achieve a
standard of 13 g/dscm (corresponding to a design level of 8.1
g/dscm). A CB system at 99 percent removal could be expected
to achieve a design level of 0.8 g/dscm to which an emissions
variability factor would be added to identify the standard. EPA
solicits comment on whether this option of applying BTF reduction based
on CI or CB to the floor levels should be adopted.
We also note that an alternative approach to using a statistically-
derived variability factor to account for emissions variability would
be to assume a more conservative control efficiency for the CI or CB
BTF technology. We believe that using a more conservative removal
efficiency could be a means to adequately account for emissions
variability given that actual emissions using the BTF control would be
expected to be lower than the assumed emission level. Under this
approach, we would more conservatively assume that CI-controlled
systems could achieve a removal efficiency of 80 percent and that CB-
controlled systems could achieve an efficiency of 90 percent. When
these removal efficiencies are applied, this would result in emission
standards of 16 g/dscm for CI-controlled systems, and 8
g/dscm for CB-controlled systems 95. We invite comment on
these alternative approaches to account for emissions variability at an
individual plant.
---------------------------------------------------------------------------
\95\ The same approach could also be utilized with the
previously discussed approach of applying the BTF control to an
assumed emission level of 300 g/dscm. When assuming the
conservative removal efficiencies of 80 percent for CI and 90
percent for CB, this would result in BTF standards of 60 g/
dscm for CI-controlled systems and 30 g/dscm for CB-
controlled systems. Again a statistically-derived variability factor
would not be added because emissions variability is accounted for by
assuming conservative removal efficiencies for CI and CB systems.
---------------------------------------------------------------------------
EPA believes that CI is a cost-effective BTF control, and is
proposing a 50 g/dscm Hg emission standard based on that
control in conjunction with a preceding estimated hazardous waste
feedrate control resulting in an emissions level of 300 g/dscm
prior to the CI control. We estimate that 57 percent of CKs are
currently meeting this level. The incremental national annualized
compliance cost for the remaining CKs to meet this level rather than
comply with the floor controls would be $7.8 million, and would provide
an incremental reduction in Hg emissions of 2100 lbs per year
nationally beyond the MACT floor controls.
We specifically are interested in comment on whether CB is a cost
effective BTF control 96. The CB-based BTF emission level would be
8 g/dscm (assuming 90 percent removal efficiency). We estimate
that 22 percent of CKs are currently meeting this level. The
incremental national annualized compliance cost for the remaining CKs
to meet this level rather than comply with the floor controls (and
proposed CI-based level of 50 g/dscm) is estimated to be $34.8
million and would provide an incremental reduction in Hg emissions
nationally of 5,100 lbs per year from the floor.
---------------------------------------------------------------------------
\96\ We also note that, while the Agency does not have
information to conclude that application of the carbon bed
technology would be problematic for cement kilns, carbon beds have
never been tested at a full-scale cement kiln. Thus, we invite
comment on the technical feasibility of CB control of Hg emissions
from CKs.
---------------------------------------------------------------------------
The Agency also invites comment on whether special consideration
should be given to kilns that may burn hazardous waste with non-detect
levels of Hg.97 Such kilns could be considered to be appropriately
regulated, with respect to Hg emissions, by only the standards the
Agency is developing for cement kilns that do not burn hazardous waste.
Thus, today's proposed Hg standards for waste-burning kilns would be
waived. To minimize implementation confusion and difficulties and to
accommodate enforcement concerns, if a CK at any time burns hazardous
waste with detectable levels of Hg, the kiln would be subject to
today's proposed rules at all times, even if it subsequently burned
waste with non-detect levels of Hg. Under the waiver, the owner and
operator would be required to sample and analyze the hazardous waste as
necessary to document that it continues to contain non-detect levels of
Hg. We invite comment on whether such a deferral to another MACT
standard (yet to be proposed for non-hazardous waste-burning CKs) is
workable, given the potential for piece-meal permitting and
enforcement.
---------------------------------------------------------------------------
\97\ We also invite comment on what minimum detection levels
would be acceptable.
---------------------------------------------------------------------------
EPA has considered costs in relation to emissions reductions and
the special bioaccumulation potential that Hg poses and determined that
proposing a BTF limit is warranted. Hg is one of the more toxic metals
known due to its bioaccumulation potential and the adverse neurological
health effects at low concentrations especially to the most sensitive
populations at risk (i.e.,
[[Page 17395]]
unborn children, infants and young children). A more detailed
discussion of human health benefits for mercury can be found in Part
Seven of today's proposal. The indirect exposure pathway resulting from
airborne deposition of Hg is of particular concern, and a particular
reason that Congress singled out Hg for priority regulation in section
112(c)(6). See S. Rep. No. 228, 101st Cong. 1st Sess. at 153-55, 166.
EPA is specifically authorized to take into account such non-air
environmental benefits in assessing when to adopt BTF standards. As
noted below, hazardous waste-burning cement kilns are a significant
source of Hg emissions, and the BTF option will control those emissions
from 75 percent over baseline and 47 percent over the floor. EPA
believes the cost of controlling this especially dangerous HAP to be
warranted in light of the extent of control, magnitude of emissions,
limited effect on cost of treating hazardous waste (and no net effect
on the cost of cement), and the fact that the control technology,
carbon injection, will also control dioxins and furans. Finally, EPA
notes that control of Hg at the BTF level should eliminate the
uncertainty presently involved in individual RCRA permitting decisions
where permit writers may develop site-specific permit limits beyond
those required by current regulations if necessary to protect human
health and the environment.
4. Semivolatile Metals
a. MACT Floor. Emissions of SVM from CKs are currently controlled
under the BIF rule. Kilns use a combination of hazardous waste feedrate
control and PM control to comply with those standards. Accordingly,
MACT floor control is based on a combination of hazardous waste
feedrate control and PM control.
The SVM emissions data for CKs includes results from 45 test
conditions collected from 26 cement plants, with a total of 34 kilns
being tested. Baseline emissions of the semivolatile metals group
(consisting of cadmium and lead) ranged from 3 g/dscm to
slightly over 6,000 g/dscm. Cadmium and lead are volatile at
the usual high temperatures within the cement kilns itself, but
typically condense onto the fine particulate at baghouse and ESP
temperatures, where they are collected. As a result, control of
semivolatile emissions is associated with PM control. However, because
of the potential for adsorption for these two metals onto the fine PM
that is less effectively collected than larger-sized PM, the control
efficiency for semivolatile metals is likely to be lower than that for
total PM. As discussed earlier, all cement plants currently use either
baghouses or ESPs to control particulate emissions.
The Agency analyzed all available Cd and Pb emissions data and
determined that sources with emission levels at or below the level
emitted by the median of the best performing 12 percent of sources used
fabric filters with air-to-cloth (A/C) ratios of 2.1 acfm/ft\2\ or less
for a kiln system with a hazardous waste MTEC of 84,000 g/dscm
or less. Analysis of emissions data from all CKs using FFs with the 2.1
acfm/ft\2\ A/C ratio and with a HW MTEC of 84,000 g/dscm or
less resulted in a floor level of 57 g/dscm.
EPA notes that raw materials and fossil fuels also contribute to
cement kiln SVM feedrates and emissions. Given that all sources must be
able to meet the floor level using the floor control, EPA investigated
whether all CKs could meet the floor level employing the MACT
technologies without being forced to substitute raw materials. Our
preliminary evaluation determined that about 10 percent of sources had
raw material containing Cd and Pb in greater concentrations than
sources in the expanded MACT pool; thus, these sources may not be able
to achieve the floor with MACT alone. 98 Before we reach any final
conclusions on this point, the Agency believes that further data are
needed on the normal, day-to-day levels of Pb and Cd in raw material
feed.
---------------------------------------------------------------------------
\98\ USEPA, ``Draft Technical Support Document for HWC MACT
Standards, Volume III: Selection of Proposed MACT Standards and
Technologies'', February 1996.
---------------------------------------------------------------------------
In addition, one approach to address this issue (of sources with
higher levels of SVM metals in their raw materials than sources in the
expanded MACT pool and that, therefore, cannot meet the floor level
using floor control) is to: (1) identify the source with the highest
normalized (by MTEC) feedrate of metals in raw material; (2) assume the
source is also feeding hazardous waste with the floor control MTEC
level of the metals; and (3) project SVM emissions from the source
based on combined raw material and hazardous waste MTECs using a
representative system removal efficiency (SRE) from the expanded MACT
pool considering an appropriate variability factor (e.g., variability
of emissions among runs within a test condition in the expanded MACT
pool). The Agency has not yet conducted this type of analysis, but
intends to do so. Again, we also believe that data reflecting normal,
day-to-day levels of Cd and Pb in raw material feed is important in
pursuing this avenue of analysis. We invite comment on this approach.
The Agency also notes that the MACT pool for SVM consists entirely
of CKs employing FF controls; that is, no cement plants with ESPs are
in the MACT pool or expanded MACT pool. EPA believes that well
designed, operated, and maintained ESPs can achieve good control of
SVMs. In fact several CKS employing ESPs in our database currently
achieve the floor level of 57 g/dscm. Because the Agency is
concerned that the SVM floor analysis may be overly exclusive (because
comparably designed and operated ESPs were not considered in the MACT
floor analysis) in identifying the floor MACT level and technology, EPA
specifically requests comment on the merits of the following
alternative floor approach. This approach identifies comparably
designed and operated ESPs (in our SVM database) equivalent to the MACT
FF (and at the MACT MTEC) and includes these sources in the analysis as
an ``equivalent technology'' of MACT. The Agency has identified an ESP
with an SCA of 500 ft\2\/kacfm or better as an equivalent technology to
the MACT FF with an A/C ratio of 2.1 acfm/ft\2\. The Agency conducted
this analysis and determined that the floor level would increase from
57 to 160 g/dscm using this approach. To meet this standard 99
percent of the time, EPA estimates that a source with average emissions
variability must be designed and operated to routinely achieve an
emission level of 99 g/dscm. EPA investigated whether all CKs
could meet the floor level employing the MACT technologies without
being forced to substitute raw materials and determined that all CKs
(in the SVM emissions database) with the exception of one kiln would be
able to meet the 160 g/dscm level using this less restrictive
MACT definition. The Agency specifically requests comment on this
alternative floor approach and floor level.
EPA recognizes that PM, SVM, and LVM emissions from cement kilns
are similarly controlled, in part, by a good PM control (e.g., ESP,
FF). The floor control for SVM (FF with an A/C ratio of 2.1 acfm/ft\2\)
offers slightly more control than the floor control for LVM (FF with an
A/C ratio of 2.3 acfm/ft\2\ or an ESP with a SCA of 350 ft\2\/kacfm).
Thus, the controls necessary to achieve the SVM MACT floor level would
appear to be governing for control of these HAPs.
EPA estimates that 33 percent of CKs are currently meeting the
floor level of 57 g/dscm. The national annualized compliance
cost for the cement kilns to
[[Page 17396]]
reduce SVM emissions to the floor level would be $13.1 million, and
would reduce national Pb and Cd emissions by 29 tons per year or 94
percent from current baseline emissions.
b. Beyond-the-Floor Considerations. The Agency considered whether
to propose a more stringent level than the floor of 57 g/dscm,
but believes that it would not be appropriate. Since control of SVM
emissions is associated with PM control, a more stringent BTF level
would require CKs to upgrade to more expensive fabric filter bags
(e.g., bags backed with a teflon membrane) or the addition of a FF for
kilns with ESPs. Even though the engineering costs to comply with a BTF
SVM level would be modest for CKs, the resulting incremental reduction
in SVM emissions from the floor level would be minimal. Thus, the
Agency believes that lowering the SVM proposed standard is not
warranted based on the minimal impact on overall SVM emissions; the
floor already provides substantial control by reducing baseline SVM
emissions by 94 percent. Thus, the Agency is proposing a MACT floor SVM
standard of 57 g/dscm for existing cement kilns.
5. Low-Volatile Metals
a. MACT Floor. Emissions of LVM from CKs are also currently
controlled under the BIF rule. Kilns use a combination of hazardous
waste feedrate control and PM control to comply with those standards.
Accordingly, MACT floor control is based on a combination of hazardous
waste feedrate control and PM control.
The Agency has LVM emissions data which consists of 45 test
conditions collected from 26 cement plants, with a total of 35 kilns
being tested. Average emissions of the low volatility metals group
(arsenic, antimony, beryllium, and chromium) ranged from 4 g/
dscm to 520 g/dscm. Due to the relatively low volatility of
these metals, more than 70 percent of these metals typically partition
to the clinker product while the remainder typically condense onto
particulate and are collected in the APCD (in this case either an ESP
or baghouse). Thus, performance of the control devices is an important
factor in controlling LVM emissions.
To identify MACT floor, EPA characterized the LVM controls used by
kilns emitting LVM at levels at or below the level emitted by the
median of the best performing 12 percent of sources. MACT floor control
is thus defined as: (1) a baghouse (i.e., fabric filter) with an air-
to-cloth ratio of 2.3 acfm/ft \2\ or less with a hazardous waste (HW)
MTEC less than 140,000 g/dscm; or (2) an ESP with specific
collection area of 350 ft \2\/kacfm with a HW MTEC less than 140,000
g/dscm. Analysis of available emissions data for all CKs
employing either of these controls resulted in a floor emissions level
of 130 g/dscm.
EPA notes that raw materials and fossil fuels also contribute to
cement kiln LVM feedrates and emissions. Given that all sources must be
able to meet the floor level using the floor control, EPA investigated
whether all CKs could meet the floor level employing the MACT controls
without being forced to substitute raw material feed. EPA determined
that all CKs would be able to meet the floor level using floor control
without switching raw materials.99
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\99\ USEPA, ``Draft Technical Support Document for HWC MACT
Standards, Volume III: Selection of Proposed MACT Standards and
Technologies'', February 1996.
---------------------------------------------------------------------------
EPA estimates that 80 percent of CKs are currently meeting the
floor level. The national annualized compliance cost for the cement
kilns to reduce LVM emissions to the floor level would be $2.8 million
for the entire hazardous waste-burning cement industry, and would
reduce LVM national emissions by 1.7 tons per year or 49 percent from
current baseline emissions.
b. Beyond-the-Floor Considerations. The Agency considered whether
to propose a more stringent level than the floor of 130 g/
dscm. We determined that proposing such a BTF level is not warranted
for several reasons: (1) It would not likely be cost effective; (2) LVM
are not of particular concern because they are not bioaccumulative; and
(3) establishing the MACT standard at the floor would not trigger the
need for a more stringent RCRA standard.
Since control of LVM emissions is associated with PM control, a
more stringent BTF level would require CKs to either install new
control equipment or to upgrade existing control equipment (e.g.,
install more expensive FF bags). Even though the engineering costs to
comply with a lower LVM BTF level would be moderate, the resulting
reduction in LVM emissions is minimal since CK LVM national emissions
are estimated to be 1.7 tons/year for the entire industry at the floor.
Thus, a LVM BTF standard is not believed to be warranted based on this
limited reduction in LVM emissions.
6. Hydrochloric Acid and Chlorine
a. MACT Floor. HCl and Cl2 (also referred to as total
chlorine) emissions from CKs are currently regulated by the BIF rule.
CKs use the natural alkalinity of the limestone raw material and
hazardous waste feedrate control (of total chlorine and chloride) to
comply with those standards. No hazardous waste-burning cement kiln
currently employs a dedicated control device (e.g., wet scrubber,
venturi scrubber) designed specifically to remove HCl/Cl2 from the
flue gas. Accordingly, MACT floor is based on hazardous waste feedrate
control.100
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\100\ Although owners and operators normally have no control
over the control provided by raw material alkalinity, we note that
kilns equipped with FFs appear to provide better control than kilns
equipped with ESPs. This may be due to the longer time of contact
between the gas stream and the alkaline dust as the gases pass
through the dust bed on the bags.
---------------------------------------------------------------------------
The Agency has HCl and Cl2 emissions data consists of 52 test
conditions collected from 26 cement plants, with a total of 35 kilns
being tested. Total chlorine emissions from cement kilns range from
less than 0.1 ppmv to 220 ppmv. To identify MACT floor, EPA identified
the highest hazardous waste feed MTEC (i.e., normalized hazardous waste
feedrate of total chlorine) used by kilns emitting HCl/Cl2 at
levels at or below the level emitted by the median of the best
performing 12 percent of sources--1.6 g/dscm. The analysis of all
available emissions data for kilns with a hazardous waste MTEC for
total chlorine of 1.6 g/dscm or less resulted in a floor emissions
level of 630 ppmv. Our data indicate that 100 percent of the test
conditions in the Agency's database are achieving this floor value.
This determination is confounding given that the highest average
emissions from any test condition in the entire database, irrespective
of hazardous waste MTEC for total chlorine, was 220 ppmv. This
anomalous finding is apparently attributable to: (1) The data set
having very high average within-test-condition variability; and (2)
adding the average variability factor to the log mean rather than the
arithmetic mean of the single test condition with the highest
arithmetic mean within the expanded MACT pool (those sources using MACT
floor control). If that source had unusually high emissions
variability, then the log mean could be substantially higher than the
arithmetic mean, resulting in an unusually high emission level to which
the variability factor was added.
Because of these concerns, the Agency invites comment on
alternative approaches that may identify a more reasonable floor level.
One approach could be to add the average variability factor for the
data set to the arithmetic mean, rather than the log mean, of the
highest test condition in the expanded
[[Page 17397]]
MACT pool. In addition, if this still resulted in a calculated floor
level greater than any emission level in the database, irrespective of
hazardous waste MTEC for total chlorine, the floor level could be
capped at the highest emission level in the database--220 ppmv.
As for the metals EPA notes that raw materials and fossil fuels
also contribute to cement kiln chlorine feedrates and emissions. Given
that all sources must be able to meet the floor level using floor
control, EPA investigated whether all CKs could meet the floor level
employing the MACT controls without being forced to substitute raw
material. As discussed above, all CKs would be able to meet the floor
level using floor control without switching raw materials.
Sources would not incur cost to comply with the proposed floor
level because it is higher than any baseline emission levels in the
entire database, and there would be no emissions reductions at the
floor level.
b. Beyond-the-Floor Considerations. The neutralization provided
naturally by alkaline raw materials essentially acts as a dry scrubber
to help control HCl/Cl2 emissions. Therefore, we do not believe
that substantial further reductions could be achieved with the use of
dry scrubber systems. Wet scrubbers, however, could be expected to
provide 99 percent or greater removal of HCl/Cl2.
BTF control is therefore being defined as a wet scrubber in
conjunction with the floor control for hazardous waste chlorine
feedrate (defined by a MTEC of 1.6 g/dscm). Given that the proposed
floor level based on hazardous waste chlorine feedrate control only
would be 630 ppmv, the resulting BTF level would be 6.3 ppmv (at 99
percent removal).
Selecting a more effective control technology such as a wet
scrubber would be expensive and the Agency believes that a BTF level
would not be appropriate. For example, in one alternate investigation,
we evaluated a 25 ppmv HCl level. The Agency estimated in that case the
national incremental annualized compliance cost to meet this level
would be $17 million. This represents HCl/Cl2 emissions reductions
of 1,900 tons per year or a 71 percent reduction from baseline
emissions. The Agency believes that the total incremental costs
associated with a standard of 6.3 ppmv would be approximately equal to
the incremental costs at a BTF level of 25 ppmv. We also note that, at
a MACT floor standard of 630 ppmv, the Agency would not be required to
establish a more stringent standard under RCRA to ensure protection of
human health and the environment.
In summary, the Agency is proposing a MACT floor HCl/Cl2
standard of 630 ppmv for existing cement kilns.
7. Carbon Monoxide and Hydrocarbons
a. MACT Floor. As discussed in Section I above, the Agency believes
that control of non-dioxin organic HAP emissions can be achieved, in
part, by establishing emissions limits on two surrogate compounds: (1)
Carbon monoxide, and (2) hydrocarbons, and also by the presence of
controls for D/F. Both CO and HCs are not listed HAPs, but the Agency
is using them as surrogates for the enumerated organic HAPs of
Sec. 112(b)(1) which can be non-D/F products of incomplete combustion
(PICs). The Agency is not proposing main stack MACT standards on carbon
monoxide for existing cement kilns for reasons discussed below;
however, those kilns with by-pass ducts would be required to either
comply with a separate CO or HC limit in the by-pass duct.
i. Carbon Monoxide in the Main Stack. The Agency is not proposing a
main stack CO limit because CO is not a universally reliable indicator
of combustion intensity and efficiency in cement kilns due to CO
generation by process chemistry and evolution from the trace organics
in the raw material feedstocks.\101\ These feedstocks can generate
large quantities of CO emissions which are unrelated to the combustion
efficiency of burning the waste and fuel. Whereas all the CO from
incinerators is combustion-generated, the bulk of the CO from cement
kilns can be the result of process events unrelated to the combustion
conditions at the burner where the wastes are introduced, or CO can be
produced from CO2 (contained in the limestone) by dissociation at
high sintering conditions. As a result, few cement kilns were able to
certify compliance with the CO standard in the BIF rule
(Sec. 266.104(b)), but instead complied with the alternative carbon
monoxide standard of Sec. 266.104(c) that allowed CO to exceed the 100
ppmv limit provided that stack gas concentrations of HCs did not exceed
20 ppmv. Thus, the Agency believes it inappropriate to establish a CO
standard measured in the main stack for all cement kilns.
---------------------------------------------------------------------------
\101\ See 56 FR at 7150, 7153-55 (February 21, 1991).
---------------------------------------------------------------------------
ii. Hydrocarbons in the Main Stack. CKs emit hydrocarbon (HC)
emissions that result from incomplete combustion of fuels and
desorption of trace levels or organic compounds from raw materials.
These HC emissions contain organic HAPs. Organics in the raw materials
are believed to be primarily from kerogen in the shale and limestone
which has a porous structure allowing for organic deposits. These
organics cause HC emissions because they are largely not destroyed
given that combustion gases flow counter-current to the raw-materials
(i.e., fuels are generally fired at the opposite end from where the raw
materials are fed).
Even when a CK is operated under good combustion conditions (and
thus is generating low or insignificant levels of fuel-related HC), HC
levels resulting from organics in the raw materials can range from 10
to 400 ppmv. This makes it problematic to use HC as the only or the
principal means to ensure good combustion efficiency of hazardous waste
fuels to minimize emissions of toxic PICs (i.e., non-D/F organic HAPs).
Wet Process Kilns and Long Dry Process Kilns. The BIF rule
currently limits HC levels in the main stack (i.e., the only kiln off-
gas stack) of wet and long dry kilns to 20 ppmv. EPA is aware of five
kilns that initially had stack HC levels exceeding the 20 ppmv limit.
Four of the kilns changed the source of shale used as raw material to
use a shale with lower organic content. (Shale comprises a small
fraction of raw material feed.) The fifth kiln feeds limestone with
(relatively) high levels of organic matter and has indicated that
transporting an alternative source of limestone to the site may be
prohibitively expensive. Other potential options, such as installing an
afterburner to destroy organics or reconstructing the kiln system to
otherwise destroy HC desorbed from the limestone, may likewise be
prohibitively expensive approaches.
EPA has determined that MACT floor for HC control for wet and long
dry kilns should be control based on the current federally-enforceable
BIF standards (i.e., control of organics in raw materials coupled with
operating under good combustion practices to minimize fuel-related HC),
and the floor level should be the BIF limit of 20 ppmv HC for such
kilns. We note further that the source could stop burning hazardous
waste and avoid having to comply with the HC floor level.
Cement Kilns with By-pass Ducts. Kilns that are equipped with a by-
pass duct (typically preheater or precalciner kilns) to divert a
portion of the kiln off-gas to a separate PM control device monitor
fuel-related HC separately from raw material-related HC. This is
because the by-pass duct diverts the kiln gas before it enters the
calcining zone where
[[Page 17398]]
the organics from the raw material are desorbed. Thus, in general,
fuel-related HC can be monitored in the by-pass duct, and raw material-
related HC can be monitored in the main stack. We invite comment on
whether hazardous waste fuel combustion by-products (e.g., chlorine)
can react with organic compounds desorbed from raw material to form
organic HAPs. If the Agency determines that hazardous waste firing can
substantially (adversely) affect emissions of organic HAPs from the
main stack, then we will consider limiting HC to 20 ppmv. This is the
limit we are proposing today for long kilns without a by-pass duct.
Monitoring HC in the by-pass is discussed later in this section.
The Agency's RCRA BIF rule does not control HC in the main stack of
cement kilns that comply with the BIF HC limit in the by-pass duct
because, under the RCRA rule, the Agency was concerned about PICs
derived from hazardous waste combustion rather than toxic organics
desorbed from raw materials. Therefore, any MACT standard for HC in the
main stack of these types of kilns must be a BTF standard since the
floor for these sources is uncontrolled, and these CKs do not otherwise
control organic HAPs in their stack emissions.
The Agency is concerned that main stack HC emissions contain HAPs
for several reasons: (1) Organics desorbed from raw materials, even
absent any influence from burning hazardous waste, contain HAPs; (2) it
is reasonable to hypothesize that the chlorine released from burning
hazardous waste can react with the organics desorbed from the raw
material to form generally more toxic chlorinated HAPs; and (3) some
preheater and precalciner kilns feed containers of hazardous waste at
the preheater or precalciner end of the kiln near the by-pass duct
entrance such that hazardous waste PICs may not have time to combust
efficiently. We are concerned that these hazardous waste PICs may be
emitted from the main stack, and that monitoring of the by-pass duct
may not be adequate to determine if inefficient combustion occurs. This
is because the by-pass duct gas may not be representative of kiln off-
gas when containers of hazardous waste are fed at the off-gas end of
the kiln.
However, the Agency does not now have sufficient data to quantify
the contribution of hazardous waste (if there is one) to HC emissions
in the main stack, and therefore to develop a MACT BTF standard for
main stack HC for this class of CKs. We are thus unable to propose
controls for HC from main stacks of cement kilns with by-pass stacks.
We invite data to remedy this situation as well as comment on this
issue. We also invite comment on an alternative of the same 20 ppmv
main stack HC standard for this class of cement kilns as for the
others.
iii. Emissions Standards for By-pass Ducts.\102\ The Agency is
proposing that cement kilns with by-pass ducts monitor and comply with
either a CO or HC concentration limit in the by-pass duct because
levels of CO and HC in the by-pass gas are more representative of
combustion efficiency than levels in the main stack.\103\ The BIF rule
currently limits HC (in the by-pass duct) to 20 ppmv.\104\ MACT floor
control is operating under good combustion conditions, including
conditions that provide adequate oxygen, temperature, turbulence, and
residence time. These controls will ensure that kilns with low organic-
containing raw materials are operating under good combustion conditions
to control PICs formed by the combustion of hazardous waste fuel.\105\
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\102\ Most precalciner and some preheater kilns are equipped
with by-pass ducts where a portion (e.g., 5 to 30 percent) of the
kiln exhaust is diverted to a separate APCD, and, sometimes, a
separate stack. These gases are typically diverted to avoid a build-
up of metal salts that can adversely affect the calcination process.
\103\ Provided that: (1) hazardous waste is fired only into the
kiln (i.e., not at any location downstream from the kiln exit
relative to the direction of gas flow); and (2) the by-pass duct gas
is representative of kiln gas. To ensure by-pass gas is
representative of kiln gas, the by-pass duct must divert a minimum
of 10 percent of kiln off-gas as currently required in the BIF rule.
See 266.104(g).
\104\ The BIF rule provides for an alternative emissions
standard for CO of 100 ppmv. See Sec. 104(f).
\105\ When the by-pass duct is vented through a separate stack,
compliance with limits on CO or HC would ensure application of MACT
regarding fuel-related organic HAPs. When the by-pass is routed back
into the main (only) stack, compliance with limits on CO or HC will
likewise ensure application of MACT regarding fuel-related organic
HAPs. Absent these controls on the by-pass duct, fuel-related
organic HAPs could be either: (1) masked by raw material-related
HAPs, if the raw material contains substantial organics; or (2) if
the raw material contains low levels of organics, the kiln could
comply with the main stack standard (if one were proposed) while
operating under poor fuel combustion conditions.
---------------------------------------------------------------------------
EPA's MACT analysis of the existing by-pass duct data of the best
performing sources resulted in a HC MACT floor level of 6.7 ppmv. The
Agency's database for CO in the by-pass is incomplete for the purposes
of calculating a statistically-derived emission limit, but we believe
that it is reasonable and appropriate to establish the by-pass CO floor
level at the same level allowed in the BIF rule--100 ppmv. Under this
standard the facility would have the option of complying with either
the CO or HC standard in the by-pass duct.
The Agency also invites comment on requiring cement kilns with by-
pass ducts to comply with both the CO and HC standard (measured in the
by-pass duct). Given that CO in the by-pass duct should be related only
to fuel combustion efficiency, monitoring of CO in addition to HC may
be appropriate to ensure complete combustion of organics in the kiln;
however, the Agency is concerned that some CO may be generated from the
CO2 by dissociation at high sintering temperatures and thus
requests information and data on this option.
Cement kiln sources would not incur costs to comply with the
proposed floor level since all cement kilns with by-pass ducts (for
which EPA has data) currently meet the floor level for either HC or CO.
EPA also notes that approximately half of cement kilns that measured
both HC and CO in the by-pass achieved the floor level.
As mentioned above, the Agency is aware of a long wet process
cement kiln that is unable to comply with either the CO limit of 100
ppmv or the HC limit of 20 ppmv in the main stack. This kiln cannot
achieve either of these levels due to the relatively high organic
matter content in the limestone. Since the majority of the raw material
fed to the kiln is limestone, substitution with an alternative source
of limestone with lower organic content is not readily feasible (e.g.,
prohibitively expensive transportation costs of a substitute raw
material). The facility attempted to retrofit the kiln with a by-pass
duct thus allowing monitoring of CO or HC in the by-pass duct as
permitted by current BIF regulations. However, efforts to construct and
engineer this kiln with a by-pass duct were not successful due to the
length of the kiln.106
---------------------------------------------------------------------------
\106\ For example, the kiln experiences a substantial increase
in length due to expansion during start-up as the kiln heats up to
operating levels.
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In coordination with state and regional officials, the cement kiln
was retrofitted with a mid-kiln sampling port that continuously draws
off a portion of the kiln combustion gas for analysis of HC or CO.
Since this sampling port does not divert a minimum of 10 percent of the
kiln off-gas from the kiln, it does not meet the Agency's current
definition of a by-pass duct defined in Sec. 266.104(g). The kiln's
mid-kiln sampling port diverts approximately 7 to 8 percent of the kiln
off-gas. The Agency specifically invites comment on allowing sources
with a mid-kiln sampling port, or other kiln gas extraction mechanism,
that is capable of continuously extracting a representative sample of
kiln off-gas to comply with
[[Page 17399]]
the same HC and CO standards proposed for kilns with by-pass ducts.
Commenters should specifically address how the gas extraction system
ensures that a representable sample of the kiln's fuel combustion gas
would be monitored for HC or CO.
b. Beyond-the-Floor Considerations. EPA has considered BTF control
for organic HAP emissions from the main stack of all CKs (including
those with by-pass ducts) based on use of a combustion gas afterburner.
We believe that a BTF level for CO of 50 ppmv and for HC of 6 ppmv are
readily achievable with an afterburner, but not appropriate. Therefore,
we are not proposing such a BTF standard. EPA has no data indicating
that any cement kilns are currently meeting these BTF levels with
existing controls. The annualized engineering costs for the cement
kilns to meet these BTF levels is estimated to be $280 million, and
would provide an incremental reduction in HC emissions nationally
beyond the floor controls of approximately 1500 tons per year and
65,000 tons per year for CO.
8. MACT Floor Cost Impacts
The total national annualized compliance costs 107 for
existing cement kilns to meet all the MACT floor levels are estimated
to be $34 million with the cost per cement kiln averaging $777,000. On
a cost per ton of hazardous waste burned, these total compliance costs
equate to $40 per ton of waste. We estimate that up to 2 cement
facilities will likely cease burning hazardous waste due to the
compliance costs associated at the floor.
---------------------------------------------------------------------------
\107\ Compliance costs represent pre-tax compliance costs.
Because compliance costs are tax-deductible, the portion of pre-tax
costs borne by the firm would be between 70 and 80 percent of the
values shown above, depending on the specific firm's margin tax
bracket. See ``Regulatory Impact Assessment for Proposed Hazardous
Waste Combustion MACT Standards'', November 13, 1995, for details.
---------------------------------------------------------------------------
The Agency is proposing to go beyond-the-floor for two pollutants
for existing cement kilns: dioxins/furans and mercury. The total
national annualized compliance costs (i.e., total costs not incremental
costs from the floor levels) to meet the dioxin/furan and mercury BTF
levels in addition to the MACT floor levels for the remaining HAPs are
estimated to be $44 million with the cost per cement kiln averaging
$1.04 million. On a cost per ton of hazardous waste burned, these total
compliance costs increase to $50 per ton of waste. Again, we estimate
that up to 2 cement facilities will likely cease burning hazardous
waste due to the compliance costs associated with the proposed
standards.
B. MACT for New Hazardous Waste-Burning Cement Kilns
This section summarizes EPA's rationale for establishing MACT for
new cement kilns for each HAP, HAP surrogate, or HAP group. Table
IV.4.B.1. summarizes the proposed emissions limits for new cement
kilns, which were determined using the analytical process described in
Part Three, Section VII and in the technical background document.
Table IV.4.B.1.--Proposed MACT Standards for New Cement Kilns
------------------------------------------------------------------------
HAP or HAP surrogate Proposed standard a
------------------------------------------------------------------------
Dioxin/furans (TEQ)....................... 0.20 ng/dscm (TEQ).
Particulate Matter........................ 69 mg/dscm (0.030 gr/dscf).
Mercury................................... 50 g/dscm.
SVM (Cd, Pb).............................. 55 g/dscm.
LVM (As, Be, Cr, Sb)...................... 44 g/dscm.b
HCl + Cl2 (total chlorides)............... 67 ppmv.
Hydrocarbons:
Main Stack c............................ 20 ppmv.
By-pass Stack d......................... 6.7 ppmv.
Carbon Monoxide:
Main Stack.............................. N/A.
By-pass Stack d......................... 100 ppmv.
------------------------------------------------------------------------
a All emission levels are corrected to 7 percent O2.
b An alternative standard of 80 g/dscm would apply if the
source elects to document compliance using a multi-metals CEM.
c Applicable only to long wet and dry process cement kilns (i.e., not
applicable to preheater and/or precalciner kilns).
d Emissions standard applicable only for cement kilns configured with a
by-pass duct (typically preheater and/or precalciner kilns). Source
must comply with either the HC or CO standard in the by-pass stack. A
long wet or long dry process cement kiln that has a by-pass duct has
the option of meeting either the HC level in the main stack or the HC
or CO limit in the by-pass duct.
1. MACT New for Dioxins/Furans
a. MACT New Floor. As for existing cement kilns, the Agency is
identifying MACT new floor for D/F based on temperature control at the
inlet to the ESP or FF. EPA characterized the single best performing
source with the lowest TEQ dioxin/furan emissions and determined that
the best performing source had an inlet temperature of 409 deg.F or
less.
The Agency then evaluated D/F emissions from all kilns that
operated the ESP or FF at 409 deg.F or less and determined that 75
percent had D/F emissions less than 0.2 ng/dscm (TEQ). The other 25
percent of kilns generally had TEQs less than 0.8 ng/dscm (TEQ),
although one kiln emitted 4.7 ng/dscm (TEQ). The Agency notes that the
MACT new expanded pool was virtually identical (with the exception of
two test conditions) to the expanded pool of existing sources.
The Agency is, therefore, identifying temperature control at the
inlet to the ESP or FF at 409 deg.F as the MACT floor control. Given
that 75 percent of sources achieve D/F emissions of 0.20 ng/dscm (TEQ)
at that temperature, the Agency believes that it is appropriate to
express the floor as ``0.20 ng/dscm (TEQ), or (temperature at the inlet
to the ESP or FF not to exceed) 409 deg.F''. This would allow sources
that operate at temperatures above 409 deg.F but that achieve the same
D/F emissions as the majority of sources that operate below 409 deg.F
(i.e., 0.20 ng/dscm (TEQ)) to meet the standard without incurring the
expense of lowering the temperature at the ESP or FF.
b. Beyond-The-Floor Considerations. The Agency has identified
activated carbon injection (CI) at less than 400 deg.F as a BTF control
for D/F for cement kilns because CI is currently used in similar
applications such as hazardous waste incinerators, municipal waste
combustors, and medical waste incinerators. The Agency is not aware of
any CK flue gas conditions that would preclude the applicability of CI
or inhibit the performance of CI that has been demonstrated for other
waste combustion applications.
Carbon injection has been demonstrated to be routinely effective at
removing greater than 95 percent of D/F and some tests have
demonstrated a removal efficiency exceeding 99 percent at gas
temperatures of 400 deg.F or less. To determine a BTF emission level,
the Agency considered the emission levels that could result from gas
temperature control to less than 400 deg.F combined with CI.
As discussed for existing sources, when CI is used in conjunction
with temperature control, an additional 95 percent reduction in
emissions could be expected. Accordingly, emissions with BTF controls
could be expected to be less than a range of 0.04 to 0.24 ng/dscm (TEQ)
(i.e., 95 percent reduction from 0.8 ng and 4.7 ng, respectively).
Given that CI reductions greater than 95 percent are readily feasible,
the Agency believes that it is appropriate to identify 0.20 ng/dscm
(TEQ) as a reasonable BTF level that could be routinely achieved.
The Agency notes that, because we have assumed a fairly
conservative carbon injection removal efficiency of 95 percent to
identify the 0.20 ng/dscm (TEQ) level, we believe that this approach
adequately accounts for emissions variability at an individual kiln
because CI removal efficiency is likely to be up to or greater than 99
percent. EPA thus believes that it is not
[[Page 17400]]
necessary to add a statistically-derived variability factor to the 0.20
ng/dscm (TEQ) level to account for emissions variability at an
individual kiln. Thus, the 0.20 ng/dscm (TEQ) BTF level represents the
proposed D/F emission standard for new cement kilns.
EPA solicits comment on this approach, and notes that if a
statistically-derived variability factor were deemed appropriate, the
BTF level of 0.20 ng/dscm (TEQ) would be expressed as a standard of
0.31 ng/dscm (TEQ). We note, however, that under this approach, it may
be more appropriate to use a less conservative CI removal efficiency
(i.e., because emissions variability would be accounted for using
statistics rather than in the engineering decision to use a
conservative CI removal efficiency), thus lowering the 0.20 ng/dscm
(TEQ) level to approximately 0.04 ng/dscm (TEQ) (i.e., 99 percent
reduction from 0.8 ng and 4.7 ng results in levels of 0.008 ng to 0.047
ng/dscm (TEQ), respectively, and 0.04 ng is a reasonable value within
this range). If so, the D/F standard would be about 0.15 ng/dscm (TEQ)
(i.e., 0.04 ng/dscm TEQ plus the variability factor of 0.11 ng/dscm
TEQ).
For similar reasons as discussed for existing cement kilns, the
Agency is proposing a BTF standard for D/F of 0.20 ng/dscm (TEQ) for
new hazardous waste-burning cement kilns. Costs for new sources are
discussed in ``Regulatory Impact Assessment for Proposed Hazardous
Waste Combustion MACT Standards''.
2. MACT New for Particulate Matter
a. MACT New Floor. The Agency analyzed all available PM emissions
data and determined that the control used by the single best performing
source used a fabric filter with an air-to-cloth (A/C) ratio of 1.8
acfm/ft\2\ or less. Analysis of emissions data from all CKs using FFs
with the 1.8 acfm/ft\2\ A/C ratio or less resulted in a level of 0.065
gr/dscf.
For similar reasons discussed for existing cement kilns, the Agency
has chosen the existing NSPS standard (an established regulatory
benchmark for PM), not the statistically-derived limit, as the MACT for
existing hazardous waste-burning cement kilns. Thus, the Agency is
identifying a MACT floor for PM and is identifying the floor level as
the NSPS limit of 69 mg/dscm (0.03 gr/dscf) because it is the lowest
federally enforceable emission standard.
b. Beyond-the-Floor Considerations. EPA considered but is not
proposing a more stringent BTF level (e.g., 35 mg/dscm (0.0105 gr/
dscf)) for new cement kilns. For the same reasons discussed for
existing sources, the Agency believes that a more stringent level than
the floor is not warranted.
3. MACT New for Mercury
a. MACT New Floor. As discussed earlier, hazardous waste-burning
cement kilns control their mercury input (and therefore much of their
emissions) through control of the mercury content in the hazardous
waste. The Agency is defining the MACT floor technology as feedrate
control with a hazardous waste MTEC less than 28 g/dscm based
on performance of the best performing source. Analysis of all existing
cement kiln sources using this hazardous waste feedrate control
resulted in a MACT new floor level of 82 g/dscm. EPA estimates
that a source with average emissions variability must be designed and
operated to routinely achieve an emission level of 58 g/dscm
to meet this standard 99 percent of the time. Expanded MACT pools are
identical. The MACT new floor analysis results in the same floor as
existing sources because their respective expanded MACT pools are
identical.
EPA solicits comment on an alternative method to establishing the
MACT new floor. Under this alternative, the floor analysis would be
similar to the approach proposed today except that the variability
factor would be added to the average emissions from the single best
performing source. By contrast, under the approach proposed today, the
variability factor is added to the emissions of the highest emitting
source in the expanded MACT pool. Thus, under this alternative the only
purpose that expanding the MACT pool would serve is to identify the
variability factor. EPA notes that this approach results in a MACT new
floor of 53 g/dscm (4.4 g/dscm (average emissions
from the best performing source) plus the statistically-derived
variability factor of 49 g/dscm).
b. Beyond-the-Floor Considerations. The Agency has considered the
same BTF control alternatives for improved Hg control for new cement
kilns: hazardous waste feedrate control of Hg in conjunction with flue
gas temperature reduction to 400 deg.F or less followed by either
carbon injection (CI) or carbon bed (CB). The BTF design emission level
under the CI-controlled option is 30 g/dscm (assuming a source
has controlled its Hg emissions to 300 g/dscm controlling Hg
feed in the hazardous waste). The BTF emission standard corresponding
to a design level of 30 g/dscm would be 50 g/dscm
108. The Agency is proposing 50 g/dscm as the MACT
standard for new cement kilns. The Agency specifically requests comment
on establishing BTF emission standards based on the alternative
approaches discussed for existing cement kilns.
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\108\ To achieve a standard of 50 g/dscm 99 percent of
the time, a source with average emissions variability must be
designed and operated to achieve an emission level of 30 g/
dscm.
---------------------------------------------------------------------------
4. MACT New for Semivolatile Metals
a. MACT New Floor. MACT new control is based on hazardous waste
feedrate control and PM control. EPA characterized the single best
performing source with the lowest SVM emissions and determined that the
best performing source used a fabric filter with an air-to-cloth ratio
of 2.1 acfm/ft \2\ or less for a kiln system with a hazardous waste
(HW) MTEC of 36,000 g/dscm or less. Analysis of all sources
(i.e., expanded MACT pool of facilities) using this technology or
better resulted in a floor level of 55 g/dscm for new cement
kilns.
EPA solicits comment on an alternative method to establishing the
MACT new floor. Under this alternative, the floor analysis would be
similar to approach proposed today except that the variability factor
would be added to the average emissions from the single best performing
source. Thus, the expanded MACT pool serves only to identify the
variability factor of the floor technology. EPA notes that this
approach results in a MACT new floor of 39 g/dscm (4
g/dscm (average emissions from the best performing source)
plus the statistically-derived variability factor of 35 g/
dscm).
b. Beyond-the-Floor Considerations. The Agency considered a more
stringent level than the floor level of 55 g/dscm based on
improved collection efficiency of the MACT floor FF. Since this level
is virtually identical to the floor level for existing sources and
considering that EPA is not proposing standards more stringent than the
floor for existing sources, the Agency believes for the same reasons
that a more stringent floor level is not warranted for new sources as
well. Finally, we note that establishing the MACT standard at the floor
would not trigger the need for a more stringent standard under RCRA.
5. MACT New for Low-Volatile Metals
a. MACT New Floor. MACT new control is based on hazardous waste
feedrate control and PM control. EPA characterized the best particulate
control device, and identified the floor technology as a baghouse
(i.e., fabric filter) with an air-to-cloth ratio of 2.3 acfm/ft\2\ or
less with a hazardous waste
[[Page 17401]]
(HW) MTEC less than 25,000 g/dscm. Analysis of the expanded
MACT pool resulted in a floor emissions level of 44 g/dscm for
new cement kilns.
EPA solicits comment on an alternative method to establishing the
MACT new floor. Under this alternative, the floor analysis would be
similar to the approach proposed today except that the variability
factor would be added to the average emissions from the single best
performing source. Thus, the expanded MACT pool only serves to identify
the variability factor of the floor technology. EPA notes that this
approach results in a MACT new floor of 30 g/dscm (4
g/dscm (average emissions from the best performing source)
plus the statistically-derived variability factor of 26 g/
dscm).
b. Beyond-the-Floor Considerations. The Agency considered a more
stringent level than the floor of 44 g/dscm based on improved
collection efficiency of the MACT floor FF. We initially determined
that selecting such a BTF level is not warranted for several reasons:
(1) It would not likely be cost effective considering the small
increment of LVMs removed; (2) LVM are not of particular concern
because they are not bioaccumulative; (3) establishing the MACT
standard at the MACT new floor would not trigger the need for a more
stringent RCRA standard.
The Agency is proposing an alternative compliance option for LVMs
for new cement kilns. Because the Agency anticipates the likelihood of
development of a multi-metals continuous emissions monitor (CEM) in the
near future and considering that the estimated detection limit for the
CEM to be approximately 80 g/dscm for the LVM metals combined,
the Agency is proposing an alternative standard of 80 g/dscm
should the source elect to document compliance using a multi-metals
CEM. Thus, the LVM standard is different depending on the compliance
method selected.
6. MACT New for Hydrochloric Acid and Chlorine
a. MACT New Floor. Cement kilns use the natural alkalinity of the
limestone used as raw material and hazardous waste feedrate control to
control HCl and Cl2 emissions. Thus, the MACT floor is based on
hazardous waste feedrate control.
EPA characterized the single best performing source with the lowest
HCl/Cl2 emissions and determined that the best performing source
used feedrate control with a hazardous waste (HW) MTEC of 1.6 g/dscm or
less. (Combined emissions of HCl and Cl2 were expressed as HCl
equivalents.) Analysis of the expanded MACT pool of facilities resulted
in a floor level of 630 g/dscm for new cement kilns, which is
the same result as for existing cement kiln sources because the
expanded MACT pools are identical for both existing and new cement
kilns.
Again, as discussed for existing cement kilns, this determination
is confounding given that the highest average emissions from any test
condition in the entire database, irrespective of hazardous waste MTEC
for total chlorine, was 220 ppmv. This anomalous finding is apparently
attributable to: (1) The data set having very high average within-test-
condition variability; and (2) adding the average variability factor to
the log mean rather than the arithmetic mean of the test condition
within the expanded MACT pool (those sources using MACT floor control)
with the highest arithmetic mean. If that source had unusually high
emissions variability, then the log mean could be substantially higher
than the arithmetic mean, resulting in an unusually high emission level
to which the variability factor was added.
Because of these concerns, the Agency invites comment on
alternative approaches that may identify a more reasonable floor level.
One approach could be to add the average variability factor for the
data set to the arithmetic mean, rather than the log mean, of the
highest test condition in the expanded MACT pool. In addition, if this
still resulted in a calculated floor level greater than any emission
level in the database, irrespective of hazardous waste MTEC for total
chlorine, the floor level could be capped at the highest emission level
in the database--220 ppmv.
b. Beyond-the-Floor Considerations. BTF control is being defined as
a wet scrubber in conjunction with the floor control for hazardous
waste chlorine feedrate. As discussed earlier for existing systems,
more stringent HCl and Cl2 control based on use of wet scrubbers
is readily achievable. The Agency is aware of two cement kilns (not
burning hazardous waste) that employ a wet and dry scrubber,
respectively, capable of HCl/Cl ![[logo] US EPA](http://www.epa.gov/epafiles/images/logo_epaseal.gif){kind=logo}