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2. Coal Distribution and Sulfur Content

In 1997, total shipments of domestic coal to coke plants, manufacturers, electricity generators, and residential/commercial consumers increased to 995 million short tons from 854 million short tons in 1988. This increase was driven by the demand for coal by the electric generators (utilities and independent power producers (1)). By 1997, electric utility generators were receiving 88 percent of the total domestic coal shipments.


Coal Demand by Region

The coal receipts by electric utility generators and all consumers vary widely across the U.S. Census Divisions (Figure 1). The share of coal received in each region, as a percent of the U.S. total, is directly related to the share of electric utility owned coal-fired generating capacity in the region (Table 1). For example, seven of the nine Census Divisions contain 98 percent of the coal-fired generating capacity and received almost 99 percent of the coal shipped to electric utility generators in 1997. New England and the Pacific Division are the two regions with less than 1 percent of the coal-fired capacity and coal receipts. The focus of this chapter is on the seven regions that account for most of the coal receipts.


Figure 1. Coal Demand Regions (Census Divisions)
Figure 1. Coal Demand Regions (Census Divisions)

Table 1. Coal Demand Regions and Relevant Characteristics, 1988, 1993, and 1997
Demand Region Total Domestic Coal Receipts Domestic Coal Received by
Electric Utility Generators		 Electric Utility Coal-Fired
Generating Net Summer Capability
Thousand Short Tons Percent of U.S. Total Thousand Short Tons Percent of U.S. Total Capability (Gigawatts) Percent of U.S. Total
1988 1993 1997 1988 1993 1997 1988 1993 1997 1988 1993 1997 1988 1993 1997 1988 1993 1997
New England 6,696 4,141 6,414 0.8 0.5 0.6 6,325 4,555 5,324 0.9 0.6 0.6 2.7 2.6 2.7 0.9 0.9 0.9
Middle Atlantic 70,253 64,421 76,487 8.2 7.3 7.7 51,532 46,511 53,687 7.1 6.1 6.1 23.0 23.0 22.9 7.8 7.6 7.6
East North Central 193,389 196,343 237,757 22.6 22.2 23.9 155,300 165,684 202,401 21.4 21.7 23.1 74.5 77.0 75.4 25.3 25.6 24.9
West North Central 112,365 116,337 131,862 13.2 13.2 13.3 99,540 101,896 120,150 13.7 13.3 13.7 34.5 34.9 35.3 11.7 11.6 11.7
South Atlantic 141,606 141,701 166,234 16.6 16.0 16.7 120,058 118,366 146,847 16.5 15.5 16.8 62.9 64.6 67.4 21.4 21.5 22.2
East South Central 85,737 97,057 108,478 10.0 11.0 10.9 73,868 86,610 102,352 10.2 11.3 11.7 35.9 36.6 36.2 12.2 12.2 11.9
West South Central 126,542 139,664 143,816 14.8 15.8 14.5 117,144 130,848 135,759 16.1 17.1 15.5 30.4 31.4 31.8 10.3 10.4 10.5
Mountain 104,271 109,200 113,046 12.2 12.4 11.4 97,184 103,137 103,539 13.4 13.5 11.8 28.4 28.8 29.3 9.7 9.6 9.7
Pacific 8,661 10,791 9,596 1.0 1.2 1.0 5,856 6,917 5,657 0.8 0.9 0.6 1.8 2.0 2.0 0.6 0.7 0.7
U.S. Total 853,930 883,934 995,181 100.0 100.0 100.0 726,806 764,524 875,717 100.0 100.0 100.0 294.2 300.9 302.9 100.0 100.0 100.0
   Notes: U.S. total coal receipts include those for which destination is unknown. U.S. total coal-fired generating capacity in Pacific Region includes non-contiguous States. Totals may not equal sum of components because of independent rounding. Domestic coal accounted for 92.3 percent of total distribution in 1997.
   Sources: Total Domestic Coal Receipts - 1988: Coal Distribution Report 1988, Table 8. Total Domestic Coal Receipts - 1993: Coal Industry Annual 1993, pp. 101-102. Total Domestic Coal Receipts - 1997: Coal Industry Annual 1997, Table 61, pp. 104-105. Coal Received By Electric Generators - 1988: Coal Distribution Report 1988, Table 8. Coal Received By Electric Generators - 1993: Coal Distribution Report 1993, (Internal), Table 8. Coal Received By Electric Generators - 1997: Coal Distribution Report 1997, (Internal), Table 8. Capacity 1997 - Inventory of Power Plants in the United States, as of January 1, 1998, Table 16.

The growth in coal receipts by electric utility generators in 1988, 1993, and 1997 is primarily due to the increased utilization of the existing electric utility owned coal-fired generating units rather than construction of new coal-fired power plants. The national average utilization rate for electric utility coal-fired power plants increased from 59.8 percent in 1988, to 62.2 percent in 1993, and 67.4 percent in 1997.(2) This increased utilization is in response to growth in the demand for electricity, as well as changes in electricity generation from other sources. The South Atlantic Division, however, did have four new electric utility owned coal-fired units come online in 1996.

Electric utilities experienced an average annual growth in retail sales of 2.2 percent between 1988 and 1997. (3) Coal-fired generation increased with this demand for electricity and maintained a national average share of total electric utility generation of 57 percent over this time period. The coal share of total electricity generation, including nonutility generation, was also constant at approximately 53 percent. (4) However, regional differences in the share of electricity produced by coal did occur between 1993 and 1997 due to changes in use of petroleum, nuclear power, and hydroelectric generation. Nuclear-powered generation declined significantly in 1997 from the previous year, because several nuclear units were shut down for all or part of 1997. In the East North Central Division, the nuclear generation was even lower in 1997 than it was in 1993, 36 billion kilowatt-hours less.(5) As a result, the coal share of total electric utility generation increased from 73 to 80 percent in that region and coal receipts by electric generators increased commensurately. In the East South Central Division, the opposite occurred. Nuclear generation increased by 36 billion kilowatthours between 1993 and 1997. Coal receipts by electric generators continued to increase, however, due to increases in demand for electricity, even as the coal share of total electric utility generation declined from 79 percent to 70 percent. In the Middle Atlantic Division, decreased oil-fired generation created more demand for coal in 1997.

This increased utilization of existing coal-fired power plants occurred at the same time that utilities were required to comply with Phase I of the CAAA90. The emission allowances allocated to each plant for Phase I are based on an emission rate of 2.5 pounds of SO2 per million British thermal units(6) consumed and the historical average fuel consumption by the plant in 1985 through 1987. During 1985, utilization rates were much lower, approximately 56 percent(7) as compared to 67 percent in 1997. Since more coal was being consumed by the coal-fired power plants in 1997 than in 1985 through 1987, additional actions had to be taken to reduce emissions to the allowance levels. Most of the coal-fired power plants affected by Phase I are located in the following five regions--Middle Atlantic, East North Central, West North Central, South Atlantic, and East South Central. A few additional coal-fired units, that were substituted for the original units named in the legislation, are located in Massachusetts and Wyoming.(8)

Figure 2. SO2 Emissions from Electric Utility Coal-Fired Steam Units, 1988-1997
Figure 2. SO2 Emissions from Electric Utility Coal-Fired Steam Units, 1988-1997

In the five key Census Divisions mentioned above, the SO2 emissions from all coal-fired plants, not just those affected by Phase I, were lower in 1995 than they were in 1988 (Figure 2). Reductions in emissions were observed even before Phase I began in 1995, as some utilities started testing lower sulfur coals in their power plants.

After 1995 the emissions from coal-fired power plants in the East North Central and the South Atlantic Divisions began to rise, however, as coal-fired generation increased to satisfy greater demand for electricity and to replace the reduced generation from nuclear plants. Although the SO2 emissions were higher, all utilities had the necessary emission allowances and were in compliance with the Phase I requirements.

The reduction in SO2 emissions has occurred, in part, through a change in the type of coal contracted for and received by electric utilities. Nationwide, the sulfur content of the coal receipts, expressed as pounds of sulfur per million Btu, declined by 13 percent between 1988 and 1997 (Table 2). Most of that decline occurred by 1993 as utilities were beginning to test new or blended coals in their plant boilers. The decline was greatest in the East North Central and West North Central Divisions, where the average sulfur content fell by 22 and 47 percent, respectively, from 1988 to 1997. The sulfur content of coal received by electric utilities in the South Atlantic and East South Central Divisions also went down over those years. The sulfur content of coal receipts in the West South Central and Mountain regions did not decline, but it was already lower than the national average. In general, those regions were not affected by the Phase I requirements, except through a few substitution units located in Wyoming. Coal-fired power plants in the Middle Atlantic region met the requirements of Phase I by installing flue gas desulfurization equipment on some of the coal-fired power plants and by obtaining additional allowances for most of the others. Although a few plants did shift to a lower sulfur coal, the average sulfur content of all coal receipts in the region did not decline from the 1988 levels.


Table 2. Average BTU and Sulfur Content of Domestic Coal Received by Electric Utilities, 1988, 1993, and 1997
Demand Region Receipts
(Thousand Short Tons)		 Average BTU
Per Pound		 Avg Sulfur Content
(Pounds Per MM BTU)
Middle Atlantic
1988 51,532 12,403 1.63
1993 46,511 12,556 R1.56
1997 53,687 12,430 1.66
East North Central
1988 155,300 11,127 R1.64
1993 R165,684 R10,886 R1.48
1997 202,401 10,588 1.28
West North Central
1988 99,540 8,710 1.16
1993 101,896 8,366 R0.75
1997 120,150 8,394 0.61
South Atlantic
1988 R120,058 R12,480 1.21
1993 R118,366 R12,482 R1.13
1997 146,847 12,329 1.05
East South Central
1988 73,868 11,912 R1.73
1993 R86,610 11,988 R1.60
1997 102,352 11,584 1.58
West South Central
1988 117,144 7,717 0.78
1993 R130,848 R7,642 R0.84
1997 135,759 7,763 0.82
Mountain
1988 97,184 9,737 0.56
1993 103,137 9,751 R0.55
1997 103,539 9,723 0.58
United States
1988 R726,806 R10,449 R1.26
1993 R764,524 R10,305 R1.15
1997 875,717 10,266 1.09
   R = Data revised since 1995 Interim Report. Revisions exclude receipts of imported coal and use an updated weighted averaging calculation.
   Notes: United States total includes the New England, Pacific Contiguous, and Pacific Noncontiguous Demand regions and coal for which the destination is unknown. Domestic coal accounted for 92.3 percent of total distribution in 1997.
   Sources: Energy Information Administration, Cost and Quality of Fuels for Electric Utility Plants 1997, DOE/EIA-0191(97) (Washington, DC, May 1998) and Cost and Quality of Fuels for Electric Utility Plants 1993, DOE/EIA-0191(93) (Washington, DC, July 1994), Tables 1, 15, and 22; Cost and Quality of Fuels for Electric Utility Plants 1988, DOE/EIA-0191(88) (Washington, DC, August 1989), Table 48.



The national average Btu per pound of coal received, i.e. the heat content of the coal, declined slightly over these years, less than 2 percent. However, this decline in the heat content of coal receipts accounts for approximately 10 percent of the increase in the tonnage of reported coal receipts. The largest decreases in heat content, of 4.8, 3.6, and 2.8 percent, occurred in three regions, East North Central, West North Central, and East South Central, respectively, between 1988 and 1997. Since coal characteristics vary across the supply regions, these changes indicate that the sources of coal supplied to the electric generators have changed. The supply and distribution patterns are described in the following sections.


Coal Supply By Region


Regions Defined

The Nation's coal supply regions are illustrated in Figure 3 and their respective contributions to 1997 total supply are contained in Table 3. Compared with coal demand regions, which are based upon State boundaries and Census Divisions, definitions of the Nation's coal supply regions are somewhat more complex. They evolved from producing district boundaries defined in the Bituminous Coal Act of 1937 and, especially in the East, were based upon the location of mining districts and their associated river and rail transportation infrastructure.

Figure 3. Coal Supply Regions
Figure 3. Coal Supply Regions


Table 3. Coal Supply Regions and Their Domestic Coal Distribution Shares, 1997
Region Coal Distribution
(Thousand Short Tons)		 Percent of
U.S. Total
Northern Appalachia 139,425 14.0
Central Appalachia 227,346 22.8
Southern Appalachia 20,875 2.1
Illinois Basin 108,282 10.9
Texas & Louisiana Lignite 57,008 5.7
Other Western Interior 2,532 0.2
Powder River Basin 318,618 32.0
North Dakota Lignite 29,172 2.9
Southwest 38,396 3.9
Rockies 48,302 4.9
Northwest 5,224 0.5
U.S. Total 995,181 100.0
   Notes: Totals may not equal sum of components because of independent rounding.
   Source: Energy Information Administration, Coal Industry Annual 1997, DOE/EIA-0584(97) (Washington, DC, December 1998), Table 61.

Regional Coal Characteristics

Despite its apparent simplicity, coal is a complex substance with myriad chemical characteristics that determine its suitability for use as a fuel and as a key ingredient in the manufacture of steel and other products. Among the most important distinguishing characteristics of coal are heat content, sulfur content, and ash content.

While a detailed examination of the Nation's coal characteristics by supply region is beyond the scope of this report, general observations about the characteristics of the Nation's coal supplies provide a useful framework for this analysis.

The Powder River Basin of Wyoming is the Nation's leading source of low-sulfur, low-Btu subbituminous coal. Coal from this region typically has a heating value in the range of 8,500 to 8,900 Btu per pound with a sulfur content of 0.3 to 0.5 pounds of sulfur per million Btu.

The Central Appalachian region, comprising roughly Virginia, the eastern portion of Kentucky, and the southern portion of West Virginia, is the Nation's primary source of bituminous coal that is relatively low in sulfur. Heat content is significantly higher than Wyoming coal. Heating values for Central Appalachian coal average approximately 12,500 Btu per pound, with a sulfur content averaging 0.85 pounds of sulfur per million Btu.

Similarly, coal from the Southern Appalachian Region, which includes Alabama and Tennessee, features an average heat content of about 12,500 Btu per pound, but a moderately higher sulfur content in the range of 0.8 to 1.2 pounds of sulfur per million Btu.

By comparison, coal from Northern Appalachia (Maryland, Ohio, northern West Virginia, and the bituminous coal regions of Pennsylvania) and from the Illinois Basin (western Kentucky, Illinois and Indiana) has a relatively high sulfur content, ranging from 1.4 to 3.5 pounds sulfur per million Btu, with heating values in the range of 11,000 to 13,000 Btu per pound.

Coals being produced from the Rockies (including primarily Colorado and Utah) and from the Southwest region are similar in sulfur content to Wyoming coal but have a substantially higher range of heating values. Southwest region subbituminous and bituminous coals range from 9,000 to 12,000 Btu per pound. Colorado and Utah bituminous coals are typically in excess of 11,000 Btu per pound. The coal-producing regions of Texas, Louisiana, and North Dakota are characterized by lignite, a brownish-black coal of low rank with a high moisture content. Heating values for currently mined lignites average about 6,500 Btu per pound.(9)

Coal Distribution Shares By Supply Region

Unlike shares of total coal demand by region, the domestic coal distribution shares attributable to the various coal supply regions changed significantly between 1988 and 1997. As shown in Figure 4, the supply regions most affected by these changes have been Northern Appalachia, the Illinois Basin, and Powder River Basin.

Figure 4. Supply Region Shares of Domestic Coal Distribution
Figure 4. Supply Region Shares of Domestic Coal Distribution

Nationwide, the share of coal from Northern Appalachia declined from 16.5 in 1988 to 13.5 percent in 1993, before rising to 14.0 percent in 1997. Similarly, the share attributable to coal fields in the Illinois Basin declined from 15.2 percent in 1988 to 10.9 percent in 1997. Concurrently, the share of distributed coal originating in the Powder River Basin increased from 24.3 percent in 1988 to 32.0 percent in 1997.

Overall, the following trends emerge from the information presented in Table 4.

  • Nationwide, the origin of domestic coal receipts by all consumers (electric utilities, independent power producers, industrial and residential/commercial users) clearly shifted from the characteristically higher sulfur Northern Appalachian and Illinois Basin regions to the lower sulfur Powder River Basin and the Rockies regions as coal consumers implemented CAAA90 compliance strategies based upon fuel switching and blending. This trend occurred in four of the five demand regions that had power plants affected by Phase I of the CAAA90.


  • In the East North Central demand region, which accounted in 1997 for nearly one-quarter of U.S. coal receipts, coal consumers shifted from Central Appalachian and Illinois Basin coal, and to a lesser extent from Northern Appalachian coal, to coal supplied from the Powder River Basin and the Rockies. The share of coal receipts supplied by Northern Appalachia declined from 20.4 percent in 1988 to 17.2 percent in 1997, while the shares supplied by Central Appalachia and the Illinois Basin declined from 28.9 percent to 22.9 percent and from 31.9 percent to 23.6 percent, respectively.

Table 4. Percentage of Demand Region Coal Receipts Coming from Each Supply Region, 1988, 1993, and 1997
Demand Region Supply Region
Northern Appalachia Central Appalachia Illinois Basin Powder River Basin Rockies Othera Total Coal
Receivedb
(Thousand
Short Tons)
Middle Atlantic
1988 87.7 12.3 0.0 0.0 0.0 0.0 70,253
1993 79.5 19.7 0.0 0.0 0.0 0.8 64,421
1997 80.0 19.5 0.0 0.0 0.0 0.5 76,487
East North Central
1988 20.4 28.9 31.9 18.7 0.1 0.0 193,389
1993 18.3 26.3 26.0 27.2 1.5 0.7 196,343
1997 17.2 22.9 23.6 34.6 1.4 0.3 237,757
West North Central
1988 0.1 1.2 16.9 50.0 0.2 31.6 112,365
1993 0.3 0.6 8.1 61.1 1.1 28.8 116,337
1997 0.2 0.6 3.5 70.5 2.3 22.9 131,862
South Atlantic
1988 22.9 65.7 11.0 0.0 0.0 0.4 141,606
1993 18.4 72.4 8.1 0.7 0.1 0.3 141,701
1997 17.9 71.7 6.3 4.0 0.0 0.1 166,234
East South Central
1988 3.7 34.2 38.3 0.0 0.0 23.8 85,737
1993 1.9 40.3 34.9 0.5 0.7 21.7 97,057
1997 3.5 30.1 33.1 10.2 4.5 18.6 108,478
West South Central
1988 0.1 0.2 0.1 52.3 1.8 45.5 126,542
1993 0.1 0.1 0.1 54.9 1.9 42.9 139,664
1997 0.2 0.1 0.8 56.1 1.6 41.2 143,816
Mountain
1988 0.0 0.3 0.0 41.1 26.9 31.7 104,271
1993 0.2 0.2 0.0 37.9 26.5 35.2 109,200
1997 0.2 0.5 0.0 38.4 27.9 33.0 113,046
United States
1988 16.5 22.8 15.2 24.3 3.9 17.3 853,930
1993 13.5 23.9 12.0 27.9 4.5 18.2 883,934
1997 14.0 22.8 10.9 32.0 4.9 15.3 995,181
   aThe principal "other" coal supply sources are: North Dakota, for the West North Central Region; Alabama, for the East South Central Region; Texas, for the West South Central Region; and Arizona and New Mexico, for the Mountain Region.
   bTotal coal includes domestic coal receipts only. Imported coal accounted for 7.7 percent of total distribution in 1997.
   Notes: United States total includes the New England and Pacific Coal Demand regions and coal for which the destination is unknown. Totals may not equal sum of components because of independent rounding.
   Sources: Energy Information Administration, Coal Industry Annual 1997, DOE/EIA-0584(97) (Washington, DC, December 1994), Table 61; and Coal Distribution January-December 1988, DOE/EIA-0125(88/4Q) (Washington, DC, March 1989), pp. 43-49.

Concurrently, the combined portion of coal supplied by the Powder River Basin and the Rockies soared from 18.8 percent in 1988 to 36 percent in 1997.

  • In the West North Central demand region, the combined share of coal demand satisfied by coal from the Illinois Basin and from indigenous sources (mostly North Dakota lignite) declined sharply (from 42.6 percent in 1988 to 26.4 percent in 1997) as the region's coal consumers turned increasingly to the Powder River Basin and the Rockies to satisfy increased coal demand and comply with the CAAA90.


  • In the East South Central region, shares of coal from Central Appalachia, the Illinois Basin, and other indigenous sources (mostly Southern Appalachia) declined in favor of sharply increased shares from the Powder River Basin and the Rockies (0 percent in 1988 to 14.7 percent in 1997).


  • In the South Atlantic demand region, the shares of coal coming from Northern Appalachia and the Illinois Basin declined while the share from the Central Appalachia increased from 65.7 percent in 1988 to 71.7 percent in 1997 and the Powder River Basin share increased from 0 to 4 percent.


  • Coal receipts in the Middle Atlantic region show a decline in the share coming from Northern Appalachia and an increase in the share coming from Central Appalachia. This shift was not caused by electric utilities complying with CAAA90, but was related more to growth in coal demand by independent power producers. In 1988, 12.3 percent of the coal shipped to Mid-Atlantic consumers came from Central Appalachia and by 1997 this share had increased to 19.5 percent. Over the same period, the share from Northern Appalachia declined from 87.7 percent to 80.0 percent.


  • In the West South Central region, increased coal demand (primarily in Texas) was satisfied with Powder River Basin coal, reducing the share attributable to indigenous sources. This region did not have any plants affected by Phase I of the CAAA90.

Transportation Mode

Table 5 presents information on the shares of coal shipments by transportation mode. As shown, railroads are the leading transporters of coal in all demand regions, accounting in 1997 for nearly 62 percent of all coal shipments. Barge and truck shipments collectively accounted for slightly more than one-quarter of coal shipments in 1997, with the balance attributable to other transportation modes, including tramways and conveyors, as well as water-borne shipments on the Great Lakes and by tidewater.

Table 5. Domestic Coal Distribution by Demand Region and Transportation Mode, 1988, 1993, and 1997
Region/Year Total
(Thousand
Short Tons)		 Percent of Total
Rail Bargea Truck Othera
Middle Atlantic
1988 70,253 37.7 25.8 21.6 14.9
1993 64,421 43.3 23.9 25.9 6.9
1997 76,486 37.9 27.8 27.0 7.3
East North Central
1988 193,389 58.0 18.1 12.5 11.4
1993 196,343 58.3 18.2 13.9 9.6
1997 237,756 63.4 14.5 13.1 9.0
West North Central
1988 112,365 65.0 6.3 6.6 22.0
1993 116,337 67.0 4.8 5.8 22.4
1997 131,682 67.3 8.2 5.2 19.3
South Atlantic
1988 141,606 71.2 15.3 5.4 8.1
1993 141,701 71.4 16.8 5.5 6.3
1997 166,235 73.8 15.8 4.9 5.5
East South Central
1988 85,737 40.2 32.9 21.5 5.3
1993 97,057 39.9 36.2 22.1 1.8
1997 108,477 47.2 33.6 15.7 3.5
West South Central
1988 126,542 69.4 4.2 10.5 15.9
1993 139,664 68.8 4.8 12.0 14.4
1997 143,816 70.2 5.1 12.3 12.4
Mountain
1988 104,271 48.2 0.0 17.7 34.1
1993 109,200 58.8 0.0 17.1 24.1
1997 113,045 56.6 0.0 17.9 25.5
U.S. Total
1988 853,930 57.5 13.5 12.3 16.1
1993 883,934 59.8 13.9 13.1 13.2
1997 995,181 61.8 13.7 12.3 12.2
   a"Barge" includes river and inland waterway shipments. "Other" includes Great Lakes and tidewater barges and colliers, tramways, conveyors, and slurry pipelines.
   Notes: U.S. total includes the New England and Pacific Census Divisions and coal for which the destination is unknown. Totals may not equal sum of components because of independent rounding.
   Source: Energy Information Administration, Coal Industry Annual 1997, DOE/EIA-0584(97) (Washington, DC, December 1998), Table 65, pp. 126-127.

Between 1988 and 1997, the most pronounced shifts in mode occurred in the East South Central, Mountain, and East North Central demand regions. In the East South Central region, the rail share of total shipments increased from 40.2 percent in 1988 to 47.2 percent in 1997. This shift occurred mostly at the expense of truck shipments, which declined in share from 21.5 percent to 15.7 percent, reflecting the shift in coal sources from Central and Southern Appalachia and the Illinois Basin to the Powder River Basin and the Rockies.

Similarly, the share of coal moving by rail to the East North Central region increased from 58 percent in 1988 to 63.4 percent in 1997, clearly reflecting the region's increased reliance upon coal from the Powder River Basin and the Rockies.

In the Middle Atlantic Region, the shares of coal moved by rail and by truck gained sharply between 1988 and 1993, largely as a result of decreased shipments by conveyor in the region. By 1997, however, the share of coal moving to the region by rail returned to roughly the level observed in 1988 as shipments by barge, and to a lesser extent by truck, gained market share.

In the Mountain region, the share of coal supplied by rail increased from 48.2 percent in 1988 to 56.6 percent in 1997 while the share supplied by other modes (primarily tramway) declined from 34.1 percent in 1988 to 25.5 percent in 1997. Most of this shift occurred between 1992 and 1993 and was attributable to a shift from tramway to rail for New Mexico coal supplied to power generators in New Mexico.

1.    Independent power producers are defined in this report as nonutility wholesale producers of electricity that are not included in the industrial or commercial sectors. They have an industrial classification code of NAICS 22 and account for approximately 2 percent of the coal consumed by electric generators in 1997.

2.    Energy Information Administration, Annual Energy Review 1999, DOE/EIA-0384(99) (Washington, DC, July 2000), Tables 8.3 and 8.6.

3.    Ibid., Table 8.9.

4.    Ibid., Tables 8.2 and 8.3.

5.    Energy Information Administration, Electric Power Annual 1993, DOE/EIA-0348(93) (Washington, DC, December 1994), Table 13. Energy Information Administration, Electric Power Annual 1997 Volume I, DOE/EIA-0348(97/1) (Washington, DC, July 1998), Table 10.

6.    British thermal unit is a measure of the heat content of a quantity of coal or other fuel. It is the quantity of heat needed to raise the temperature of 1 pound of water by 1 F at or near 39.2 F. Also,2.5 pounds of SO2 emissions are equivalent to 1.25 pounds of sulfur. In the coal (assumingcomplete combustion).

7.  Energy Information Administration, Inventory of Power Plants in the United States 1985, DOE/EIA-0095(85) (Washington, DC, August 1986), Table 1. Energy Information Administration, Annual Energy Review 1999, DOE/EIA-0384(99) (Washington, DC, July 2000), Table 8.3.

8.  Energy Information Administration, The Effects of Title IV of the Clean Air Act Amendments of 1990 on Electric Utilities: An Update, DOE/EIA-0582(97) (Washington, DC, March 1997), Table B1.

9.  Sulfur and Btu values based on coal delivered to electric utilities. Energy Information Administration,Cost and Quality of Fuels for Electric Utility Plants 1998 Tables, DOE/EIA-0191 (Washington, DC, June 1999), Table 23.