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Alternatives to Traditional Transportation Fuels 1994
Volume 2
Greenhouse Gas Emissions
Volume 2
Greenhouse Gas Emissions
In the United States, transportation is a multimodal system of highway, mass transit, air, rail, waterborne, and pipeline transport. Light trucks [39] are becoming a greater proportion of the surface transportation fleet, accounting for almost 40 percent of new vehicle purchases. These vehicles, as well as conventional automobiles (collectively known “light-duty” vehicles), are the basis in this report for GHG emissions resulting from fuel combustion.
In 1990, highway travel accounted for 85 percent of total passenger miles traveled, air travel for 11 percent, and rail and bus travel for 4 percent. In addition, more than 3.1 trillion ton-miles of freight are moved in the United States each year. A 50-percent increase in vehicle miles traveled since 1969 has been partly offset by a 34 percent decrease (equivalent to an increase in efficiency of 7 miles per gallon) in the amount of fuel consumed per mile. Fossil fuels account for approximately 85 percent of U.S. energy consumed, with the remaining 15 percent coming from renewable and other energy sources [40].
Motor vehicle greenhouse gas (GHG) emissions are projected to grow in the United States and throughout the world as the result of increasing vehicle miles traveled (VMT). EIA projects a 1.4 percent VMT growth per year from 1994 to 2015 in the U.S. compared with a 5.5 percent growth rate between 1980 and 1990 [41]. The 1990 Nationwide Personal Transportation Survey (NPTS) [42] suggests that vehicle miles traveled will increase at a rate about double the population growth. The greatest growth in vehicle miles traveled is expected to come from non-work-related trips and increases in commuting distances, which are associated with suburban sprawl. These trends are occurring not only in the United States but also in all major cities around the world and promise to continue even if economic growth is minimal. Moreover, the rate of increase in vehicle ownership in Asia and Africa is greater than in the United States and elsewhere (Table 4). Removing the 55 mile-per-hour speed limit will also add to GHG emissions' growth.
| Table 4. Worldwide Vehicle Ownership Trends (Vehicles per Person) | |||
|---|---|---|---|
| Area | 1980 | 1990 | Percent Change |
| Africa | 0.013 | 0.021 | 61.5 |
| Asia | 0.019 | 0.033 | 73.7 |
| United States | 0.588 | 0.769 | 30.8 |
| South America | 0.067 | 0.083 | 23.9 |
| Europe | 0.217 | 0.278 | 28.0 |
| Source: Decision Analysis Corporation, Measurement of Emissions: Greenhouse Gas Estimates for Alternative Transportation Fuels, unpublished final report prepared for the Energy Information Administration (Vienna, VA, December 1995). | |||
The transportation sector contributes about one-third of total carbon dioxide emissions in the United States and other countries that belong to the Organization for Economic Cooperation and Development [43]. Annual worldwide carbon dioxide produced from motor vehicle use is estimated at around 0.32 trillion moles (14 trillion grams), or about 20 percent of total carbon dioxide production [44].
GHGs contribute to the greenhouse effect through different amplification rates (effectivenesses) over varying time periods (Table 5). These total effects are referred to as “weighted,” or the GWP of each GHG. One of the main reasons for weighting GHGs is that each gas absorbs radiation at a different energy level, with a different coefficient of absorption, and has a different residence time, or decay time, in the atmosphere. Although weighting is the best way to estimate the actual effect of various GHGs, the assumptions needed to arrive at GWP values for some GHGs (e.g., methane and nitrogen oxides) are at best very approximate. Recent data on atmospheric methyl chloroform concentrations indicate that hydroxyl radical (OH*) concentrations are about 20 percent greater than previously estimated, and the revision of these data leads to the projection of a shorter atmospheric methane lifetime than previously estimated [45] [46]. These findings suggest that the actual greenhouse effects for methane, nonmethane hydrocarbons, and oxides of nitrogen are probably lower than the values presently used because the residence times for these GHGs were developed based on lower estimates of hydroxyl radical concentration in the atmosphere.
| Table 5. Greenhouse Gases and Their Potential Contribution to Global Warming | |||||
|---|---|---|---|---|---|
| Greenhouse Gas | Relative Effectivenessa | Decay Timeb (years) | Relative Contributionc in 100 Years | ||
| per Kilogram | per Mole | per Kilogram | per Mole | ||
| Carbon Dioxide (CO2) | 1 | 1 | 120-500d | 1 | 1 |
| Methane (CH4) | 70 | 25 | 7-14.5 | 15-30 | 5-10 |
| Nitrous Oxide (N2O) | 210 | 210 | 120 | 320 | 320 |
| Ozone (O3) | 1,800 | 2,000 | 0.01 | 3 | 4 |
| CFC-11 | 4,000 | 12,000 | 50 | 4,000 | 11,000 |
| CFC-12 | 6,000 | 15,000 | 102 | 8,500 | 21,250 |
| aThe greenhouse
effectiveness of a gas in the atmosphere depends, in part, on its
concentration. As the atmospheric concentration of a gas increases,
the effectiveness of additional gas decreases. The relative effectiveness
means the effectiveness of a greenhouse gas relative to carbon dioxide.
The relative effectiveness refers to global warming potential (GWP)
of a gas relative to carbon dioxide GWP. bThe decay time is a rough measure of how long the greenhouse gas remains in the atmosphere. If the decay time is 150 years, one-half of the initial amount remains in the atmosphere after 150 years. cThe relative contribution is the accumulated greenhouse effect as the integral of the greenhouse effect over time, when each gas is undergoing an exponential decrease, while at the same time being added to by continuing industrial emissions. dH. Rhode, “A Comparison of the Contribution of Various Gases to the Greenhouse Effect,” Science 248 (1990):1217-1219. U.S. Department of Energy, A Primer on Greenhouse Gases, DOE/NBB-0083 (Washington, DC, March 1988). CFC-11 = CCl3F. CFC-12 = CCl2F2. Note: Global warming potential for water vapors is not available. Sources: David M. Gates, Climate Change and Its Biological Consequences (Sunderland, MA: Sinauer Associates Publishers, Inc. 1993), p. 9; Energy Information Administration, Emissions of Greenhouse Gases in the United States 1987-1994, DOE/EIA-0573(87-94) (Washington, DC, October 1995), p. 6. |
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The two most important variables in calculating the GWP of a greenhouse gas are its “instantaneous radiative forcing” and atmospheric residence time (see Appendix A for details). Radiative forcing values greatly depend not only on GHG concentrations (including absorption bands overlap and reactivity of GHGs), but also on the vertical (altitude) and horizontal distribution of GHGs (see Appendix D for details about the overlap of the absorption bands of GHGs). Except for carbon dioxide, all other major GHG vertical and horizontal (i.e., altitude and surface area, respectively) distribution profiles vary greatly. The radiative forcing may be a function of horizontal and vertical distribution of greenhouse gases, leading to variable GWPs at different locations. The variable GWP values will actually be very useful in estimating or forecasting regional impacts of GHGs.
The estimates presented in Table 1 show both unweighted and weighted GHG emissions [47], while Tables 7 through 12 show only unweighted emissions. (To obtain weighted estimates, apply the GWPs from Table 5.) The unweighted estimate measures contributions from all GHGs simply as moles and grams of emissions for the fuel consumed per VMT. The unweighted estimate is a good place to begin GHG analysis, particularly because the GWPs of methane, nitrogen oxides, and water vapor are subject to considerable uncertainty and require scientific investigation beyond the scope of the Energy Information Administration (EIA).
Greenhouse Gas Emissions From Alternative Transportation Fuels and Gasoline
EIA began its effort to estimate GHG emissions from replacement fuels in 1993 by examining existing literature on the subject and developing information specific to alternative transportation fuels (ATFs) across the fuel cycle [48]. In general, this work paralleled the framework established by Delucchi [49]. Estimates of GHGs are not based upon actual measurements from operating vehicles, but rather on the simplified chemistry of hydrocarbon combustion in automotive engines as formalized in the U.S. Environmental Protection Agency (EPA) “Mobile 5a” emission model [50]. A brief overview of the combustion chemistry of alternative and traditional transportation fuels is presented in Appendix C.
EIA uses the Decision Analysis Corporation (DAC) emissions model [51] for the estimation of greenhouse gases emitted from the end-use of alternative and traditional transportation fuels because the Mobile 5a model does not provide fully for alternative transportation fuels. EIA then combines this result with its previous estimates [52] based on Delucchi's model to obtain the emissions from the remaining stages of the total fuel cycle. The DAC emissions model first calculates theoretical amounts of CO2 and water emitted from vehicles per million Btu of fuel consumption, assuming perfect combustion. Carbon dioxide and water emissions per million Btu are then converted to emissions in grams and/or moles [53] per VMT based on assumptions about miles per gallon, relative efficiencies of different fuels, and the density of gasoline. EIA then estimates criteria pollutant emissions in grams and/or moles per VMT for the different alternative fuels, based on the average emission rate observed in an alternate transportation fuel vehicles database [54]. Criteria pollutants from gasoline are provided in the model. Evaporative emissions obtained from EPA's Mobile 5a model for different liquid fuels are then added to arrive at total vehicle emission estimates [55]. The DAC emissions model then adjusts the theoretical water and carbon dioxide emissions to account for all criteria pollutants and evaporative emissions.
Carbon dioxide and water vapor account for more than 97 percent of alternative and traditional transportation fuel combustion products (Tables 6, 7, and 8). Water vapor production from gasoline-fueled vehicle combustion is of the same magnitude as carbon dioxide; that is, they are roughly equimolar combustion products, each totaling approximately 17.34 x 1012 moles per year in the world and 5.63 x 1012 moles per year in the United States [56].
| Table 6. Gasoline Exhaust Products per Vehicle Mile Traveled (Grams and Moles) | ||||
|---|---|---|---|---|
| Exhaust Product | Emissions | |||
| Grams | Percent of Total | Moles | Percent of Total | |
| Carbon Dioxide (CO2) | 272.38 | 69.38 | 6.19 | 49.01 |
| Water Vapor (H2O) | 109.42 | 27.88 | 6.08 | 48.14 |
| Methane (CH4) | 0.08 | 0.02 | <0.01 | 0.07 |
| Nitrogen Oxides (NOx) and Nitrous Oxide (N2O) | 0.87 | 0.22 | 0.02 | 0.16 |
| Carbon Monoxide (CO) | 9.00 | 2.29 | 0.32 | 2.53 |
| Nonmethane Hydrocarbons (CnHm) | 0.86 | 0.21 | 0.01 | 0.09 |
| Notes: Gasoline refers to
unleaded gasoline in this report. Estimates are based on the Environmental
Protection Agency's Mobile 5a model for emissions produced by hydrocarbon
combustion in automotive engines. Nitrogen oxides include primarily
nitric oxide and nitrogen dioxide. One mole of gas is equal to the
amount of substance that contains as many elementary units (6.023
x 1023 molecules or atoms as there are atoms in 12 grams
of carbon-12. Normally, emissions are reported in grams per vehicle
mile traveled. However, reporting in moles is preferable because greenhouse
gas heat absorption is directly related to the number of molecules
of gas. Source: Decision Analysis Corporation, “Measurement of Emissions: Greenhouse Gas Estimates for Alternative Transportation Fuels,” unpublished final report prepared for the Energy Information Administration (Vienna, VA, December 1995). |
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Table 7 and Figure 3 show the total carbon dioxide emissions per VMT for the entire fuel cycle for different fuels. For the entire fuel cycle, CNG produces the lowest carbon dioxide emissions, or 5.64 moles (248.2 grams) per VMT, closely followed by liquefied petroleum gas (LPG) at 6 moles (263.5 grams) per VMT. Compressed natural gas (CNG) and LPG follow similar trends in the vehicle stage [57]. Alcohol fuels emit less carbon dioxide in the vehicle stage than gasoline. Total carbon dioxide emissions for the fuel cycle from corn-based ethanol is smaller than from gasoline. Ethanol from corn produces the lowest amount of carbon dioxide emissions in the pre-vehicle stage at 0.56 moles (24.4 grams) per VMT due to the sequestration carbon dioxide credit of 6.8 moles (299.1 grams), followed by LPG at 0.65 moles (28.1 grams) and CNG at 0.99 moles (43.5 grams).
Total fuel cycle water vapor emissions are the lowest for gasoline at 7.75 moles (139.5 grams) followed by LPG at 8.18 moles (147.3 grams) and CNG at 10.93 moles (196.8 grams) (Table 8 and Figure 3). Currently, however, water vapor from fuel combustion is not believed to have a significant impact on atmospheric water vapor concentrations.
All other emissions are best represented by millimoles (one-thousandth of a mole) and milligrams (one-thousandth of a gram) rather than moles and grams. LPG emits the least methane, 17.2 millimoles (271 milligrams) per VMT, followed by gasoline at 22 millimoles (349 milligrams) per VMT (Table 9, Figure 4). CNG tops the list for methane emissions, producing 56.3 millimoles (900 milligrams) per VMT in the vehicle stage and 35 millimoles (559 milligrams) per VMT in other stages. Corn-based ethanol emits the largest amount of nitrous oxide, 9.3 millimoles (410 milligrams) per VMT, largely due to fertilizer use (7.41 millimoles or 327 milligrams per VMT) (Table 10 and Figure 4). Because actual measurements of nitrous oxide in the vehicle stage vary greatly, the regulatory maximum of 1.6 millimoles (70 milligrams) per VMT is used to calculate nitrous oxide emissions.
Table 11 shows the carbon monoxide emissions for the various fuels as being identical--321.4 millimoles (9,000 milligrams) per VMT in the vehicle stage. The reason is that the value shown is the regulatory maximum set within the model with a value of 321.4 millimoles (9,000 milligrams) per VMT. These emissions are not measured values due to the huge range of values reported in the alternative-fueled vehicles (AFVs) database. Ethanol has the lowest total fuel cycle carbon monoxide emissions at 258.3 millimoles (7,232 milligrams) per VMT (Figure 5).
Total fuel cycle nitric oxide and nitrogen dioxide emissions for LPG and CNG are lowest at 22.9 millimoles (870 milligrams) and 24.2 millimoles (919 milligrams), respectively, per VMT, mainly because the vehicle stage uses the regulatory maximum value of 21.1 millimoles (800 milligrams) per VMT (Table 12 and Figure 5). Ethanol from corn emits the most nitrogen oxides--37.2 millimoles (1,417 milligrams) per VMT-- due to large releases during the corn-growing and fuel production (fermentation) processes. At 1.8 millimoles (70 milligrams) per VMT, LPG emits the least nitrogen oxides prior to the vehicle stage of the fuel cycle.
An evaluation of available data on total fuel cycle emissions for five fuel types (namely, gasoline, CNG, LPG from oil and gas, methanol from natural gas, and ethanol from corn) and combustion chemistry results in certain conclusions with respect to existing information on GHGs in the transportation sector. First, ATFs would produce minimal, if any, weighted GHG reductions if water vapor were taken into account. For a variety of reasons, however, most current analyses of GHGs do not include water vapor as a greenhouse gas in analyzing fuel emissions. For instance, some analysts question whether the marginal addition of water vapor from fuels, except emissions from high-flying aircraft [58], has a measurable impact, compared with the impact of “background” levels of water vapor in the atmosphere. The relation between surface sources and atmospheric concentrations of water vapor is complicated and indirect. Second, CNG produces the lowest level of carbon dioxide emissions across the total fuel cycle, followed by LPG and ethanol from corn. Third, CNG produces the largest methane emissions across the total fuel cycle. Finally, ethanol from corn produces the largest nitrous oxide emissions across the total fuel cycle.
| Table 7. Fuel Cycle Carbon Dioxide Emissions per Vehicle Mile Traveled (Grams and Moles) | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Fuel Cycle Stage | Gasoline | Methanol From Natural Gas | Ethanol From Corn | Compressed Natural Gas | LPG From Oil and Gas | |||||
| Grams/ VMT |
Moles/ VMT |
Grams/ VMT |
Moles/ VMT |
Grams/ VMT |
Moles/ VMT |
Grams/ VMT |
Moles/ VMT |
Grams/ VMT |
Moles/ VMT |
|
| CO2 From Natural Gas Wells | 0.0 | 0.00 | 6.3 | 0.14 | 0.0 | 0.00 | 4.5 | 0.10 | 2.9 | 0.07 |
| Gas Leaks and Flaresa | 3.5 | 0.08 | 0.0 | 0.00 | 0.0 | 0.00 | 0.0 | 0.00 | 0.9 | 0.02 |
| Fertilizer Manufacture | 0.0 | 0.00 | 0.0 | 0.00 | 57.0 | 1.30 | 0.0 | 0.00 | 0.0 | 0.00 |
| N2O, NOx, CO2 From Fertilizer | 0.0 | 0.00 | 0.0 | 0.00 | 0.0 | 0.00 | 0.0 | 0.00 | 0.0 | 0.00 |
| Feedstock Recovery | 10.0 | 0.23 | 15.9 | 0.36 | 10.8 | 0.25 | 6.2 | 0.14 | 6.4 | 0.15 |
| Feedstock Transmission | 8.7 | 0.20 | 4.8 | 0.11 | 13.7 | 0.31 | 0.0 | 0.00 | 2.2 | 0.05 |
| Fuel Production | 47.8 | 1.09 | 62.5 | 1.42 | 226.1 | 5.14 | 5.4 | 0.12 | 10.0 | 0.23 |
| Sequestrationb | 0.0 | 0.00 | 0.0 | 0.00 | -299.1 | -6.80 | 0.0 | 0.00 | 0.0 | 0.00 |
| Fuel Distribution | 4.9 | 0.11 | 23.2 | 0.53 | 15.9 | 0.36 | 8.7 | 0.20 | 5.7 | 0.13 |
| Compression or Liquefaction | 0.0 | 0.00 | 0.0 | 0.00 | 0.0 | 0.00 | 18.7 | 0.43 | 0.0 | 0.00 |
| Subtotal | 74.9 | 1.71 | 112.7 | 2.56 | 24.4 | 0.56 | 43.5 | 0.99 | 28.1 | 0.65 |
| Vehiclec,d,e | 272.4 | 6.19 | 270.4 | 6.15 | 301.1 | 6.84 | 204.7 | 4.65 | 235.4 | 5.35 |
| Total | 347.3 | 7.90 | 383.1 | 8.71 | 325.5 | 7.40 | 248.2 | 5.64 | 263.5 | 6.00 |
| aAssumes that
flared gas is burned completely to CO2 and water vapor
with no methane, nonmethane organic components, or carbon monoxide. bSequestration refers to the fixation process of greenhouse gases emitted (e.g., carbon dioxide and water vapors are sequestered through photosynthesis). cDecision Analysis Corporation, “Measurement of Emissions: Greenhouse Gas Estimates for Alternative Transportation Fuels,” unpublished final report prepared for the Energy Information Administration (Vienna, VA, December 1995). dGreenhouse gas (GHG) emission values from vehicle end-use are revised. eThe total GHG emission values are revised because vehicle end-use values are revised. CO2 = Carbon dioxide. LPG = Liquefied petroleum gases. N2O = Nitrous oxide. NOx = Nitrogen oxides. VMT = Vehicle mile traveled. Notes: Gasoline refers to unleaded gasoline in this report. • Table was derived using a vehicle with gasoline efficiency of 30 miles per gallon. • Emissions from manufacturing the vehicles are not included. • Nitrogen oxides include primarily nitric oxide and nitrogen dioxide. One mole of a gas is equal to the amount of substance that contains as many elementary units (6.023 x 1023 molecules or atoms) as there are atoms in 12 grams of carbon-12. Normally, emissions are reported in grams per VMT. However, reporting in moles is preferable because GHG heat absorption is directly related to the number of molecules of a gas. Sources: Derived from GHG emissions spreadsheet provided to the Energy Information Administration, July 1994. Spreadsheet is an unpublished revision of Argonne National Laboratory, Center for Transportation Research, Emissions of Greenhouse Gases From the Use of Transportation Fuels and Electricity, ANL/ESD/TM-22, prepared by Dr. Mark Delucchi, Vol. 1 (Argonne, IL, November 1991) and Vol. 2 (Argonne, IL, November 1993). Also see Energy Information Administration, Alternatives to Traditional Transportation Fuels 1993, EIA/DOE-0585(93) (Washington, DC, January 1995). |
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| Table 8. Fuel Cycle Water Vapor Emissions per Vehicle Mile Traveled (Grams and Moles) | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Fuel Cycle Stage | Gasoline | Methanol From Natural Gas | Ethanol From Corn | Compressed Natural Gas | LPG From Oil and Gas | |||||
| Grams/ VMT |
Moles/ VMT |
Grams/ VMT |
Moles/ VMT |
Grams/ VMT |
Moles/ VMT |
Grams/ VMT |
Moles/ VMT |
Grams/ VMT |
Moles/ VMT |
|
| CO2 From Natural Gas Wells | 0.0 | 0.00 | 2.5 | 0.14 | 0.0 | 0.00 | 1.8 | 0.10 | 1.2 | 0.7 |
| Gas Leaks and Flaresa | 1.4 | 0.08 | 0.0 | 0.00 | 0.0 | 0.00 | 0.0 | 0.00 | 0.4 | 0.02 |
| Fertilizer Manufacture | 0.0 | 0.00 | 0.0 | 0.00 | 22.9 | 1.27 | 0.0 | 0.00 | 0.0 | 0.00 |
| N2O, NOx, CO2 From Fertilizer | 0.0 | 0.00 | 0.0 | 0.00 | 0.0 | 0.00 | 0.0 | 0.00 | 0.0 | 0.00 |
| Feedstock Recovery | 4.0 | 0.22 | 6.4 | 0.36 | 4.3 | 0.24 | 2.5 | 0.14 | 2.6 | 0.14 |
| Feedstock Transmission | 3.5 | 0.19 | 1.9 | 0.11 | 5.5 | 0.31 | 0.0 | 0.00 | 0.9 | 0.05 |
| Fuel Production | 19.2 | 1.07 | 25.1 | 1.39 | 90.8 | 5.04 | 2.2 | 0.12 | 4.0 | 0.22 |
| Sequestrationb | 0.0 | 0.00 | 0.0 | 0.00 | -120.1 | -6.67 | 0.0 | 0.00 | 0.0 | 0.00 |
| Fuel Distribution | 2.0 | 0.11 | 9.3 | 1.29 | 6.4 | 0.36 | 3.5 | 0.19 | 2.0 | 0.13 |
| Compression or Liquefaction | 0.0 | 0.00 | 0.0 | 0.00 | 0.0 | 0.00 | 7.5 | 0.42 | 0.0 | 0.00 |
| Subtotal | 30.1 | 1.67 | 45.2 | 3.29 | 9.8 | 0.55 | 17.5 | 0.97 | 11.1 | 0.63 |
| Vehiclec,d,e | 109.4 | 6.08 | 232.9 | 12.94 | 301.1 | 16.73 | 179.3 | 9.96 | 135.9 | 7.55 |
| Total | 139.5 | 7.75 | 278.1 | 16.23 | 310.9 | 17.28 | 196.8 | 10.93 | 147.0 | 8.18 |
| aAssumes that
flared gas is burned completely to CO2 and water vapor
with no methane, nonmethane organic components, carbon monoxide, NOx,
or N2O. bSequestration refers to the fixation process of greenhouse gases emitted (e.g., carbon dioxide and water vapors are sequestered through photosynthesis). Water vapor sequestration through photosynthesis is the only process considered in this report. There may be other processes that merit consideration. cDecision Analysis Corporation, “Measurement of Emissions: Greenhouse Gas Estimates for Alternative Transportation Fuels,” unpublished final report prepared for the Energy Information Administration (Vienna, VA, December 1995). dGreenhouse gas (GHG) emission values from vehicle end-use are revised. eThe total GHG emission values are revised because vehicle end-use values are revised. CO2 = Carbon dioxide. LPG = Liquefied petroleum gases. N2O = Nitrous oxide. NOx = Nitrogen oxides. VMT = Vehicle mile traveled. Notes: Gasoline refers to unleaded gasoline in this report. • Table was derived using a vehicle with gasoline efficiency of 30 miles per gallon. • Emissions from manufacturing the vehicles are not included. • Nitrogen oxides include primarily nitric oxide and nitrogen dioxide. One mole of a gas is equal to the amount of substance that contains as many elementary units (6.023 x 1023 molecules or atoms) as there are atoms in 12 grams of carbon-12. Normally, emissions are reported in grams per VMT. However, reporting in moles is preferable because GHG heat absorption is directly related to the number of molecules of a gas. Sources: Derived from GHG emissions spreadsheet provided to the Energy Information Administration, July 1994. Spreadsheet is an unpublished revision of Argonne National Laboratory, Center for Transportation Research, Emissions of Greenhouse Gases From the Use of Transportation Fuels and Electricity, ANL/ESD/TM-22, prepared by Dr. Mark Delucchi, Vol. 1 (Argonne, IL, November 1991) and Vol. 2 (Argonne, IL, November 1993). Also see Energy Information Administration, Alternatives to Traditional Transportation Fuels 1993, EIA/DOE-0585(93) (Washington, DC, January 1995). |
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| Table 9. Fuel Cycle Methane Emissions per Vehicle Mile Traveled (Milligrams and Millimoles) | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Fuel Cycle Stage | Gasoline | Methanol From Natural Gas | Ethanol From Corn | Compressed Natural Gas | LPG From Oil and Gas | |||||
| mg/ VMT |
mmol/ VMT |
mg/ VMT |
mmol/ VMT |
mg/ VMT |
mmol/ VMT |
mg/ VMT |
mmol/ VMT |
mg/ VMT |
mmol/ VMT |
|
| CO2 From Natural Gas Wells | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 |
| Gas Leaks and Flaresa | 178 | 11.1 | 367 | 22.9 | 0 | 0.0 | 490 | 30.6 | 169 | 10.6 |
| Fertilizer Manufacture | 0 | 0.0 | 0 | 0.0 | 100 | 6.3 | 0 | 0.0 | 0 | 0.0 |
| N2O, NOx, CO2 From Fertilizer | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 |
| Feedstock Recovery | 16 | 1.0 | 3 | 0.2 | 0 | 0.0 | 1 | 0.1 | 5 | 0.3 |
| Feedstock Transmission | 9 | 0.6 | 30 | 1.9 | 16 | 1.0 | 0 | 0.0 | 2 | 0.1 |
| Fuel Production | 62 | 3.9 | 37 | 2.3 | 405 | 25.3 | 1 | 0.1 | 7 | 0.4 |
| Sequestration | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 |
| Fuel Distribution | 4 | 0.0 | 30 | 1.9 | 20 | 1.3 | 40 | 2.5 | 7 | 0.4 |
| Compression or Liquefaction | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 27 | 1.7 | 0 | 0.0 |
| Subtotal | 269 | 16.6 | 467 | 29.2 | 541 | 33.9 | 559 | 35.0 | 190 | 11.8 |
| Vehicleb,c,d | 80 | 5.4 | 80 | 5.4 | 80 | 5.4 | 900 | 56.3 | 80 | 5.4 |
| Total | 349 | 22.0 | 547 | 34.6 | 621 | 39.3 | 1,459 | 91.3 | 270 | 17.2 |
| aAssumes that
flared gas is burned completely to CO2 and water vapor
with no methane, nonmethane organic components, carbon monoxide, NOx,
or N2O. bDecision Analysis Corporation, “Measurement of Emissions: Greenhouse Gas Estimates for Alternative Transportation Fuels,” unpublished final report prepared for the Energy Information Administration (Vienna, VA, December 1995). cGreenhouse gas (GHG) emission values from vehicle end-use are revised. dThe total GHG emission values are revised because vehicle end-use values are revised. CO2 = Carbon dioxide. LPG = Liquefied petroleum gases. mg = Milligrams. mmol = Millimoles. N2O = Nitrous oxide. NOx = Nitrogen oxides. VMT = Vehicle mile traveled. Notes: Gasoline refers to unleaded gasoline in this report. • Table was derived using a vehicle with gasoline efficiency of 30 miles per gallon. • Emissions from manufacturing the vehicles are not included. • Nitrogen oxides include primarily nitric oxide and nitrogen dioxide. One mole of a gas is equal to the amount of substance that contains as many elementary units (6.023 x 1023 molecules or atoms) as there are atoms in 12 grams of carbon-12. Normally, emissions are reported in grams per VMT. However, reporting in moles is preferable because GHG heat absorption is directly related to the number of molecules of a gas. Sources: Derived from GHG emissions spreadsheet provided to the Energy Information Administration, July 1994. Spreadsheet is an unpublished revision of Argonne National Laboratory, Center for Transportation Research, Emissions of Greenhouse Gases From the Use of Transportation Fuels and Electricity, ANL/ESD/TM-22, prepared by Dr. Mark Delucchi, Vol. 1 (Argonne, IL, November 1991) and Vol. 2 (Argonne, IL, November 1993). Also see Energy Information Administration, Alternatives to Traditional Transportation Fuels 1993, EIA/DOE-0585(93) (Washington, DC, January 1995). |
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| Table 10. Fuel Cycle Nitrous Oxide Emissions per Vehicle Mile Traveled (Milligrams and Millimoles) | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Fuel Cycle Stage | Gasoline | Methanol From Natural Gas | Ethanol From Corn | Compressed Natural Gas | LPG From Oil and Gas | |||||
| mg/ VMT |
mmol/ VMT |
mg/ VMT |
mmol/ VMT |
mg/ VMT |
mmol/ VMT |
mg/ VMT |
mmol/ VMT |
mg/ VMT |
mmol/ VMT |
|
| CO2 From Natural Gas Wells | 0 | 0.0 | 0 | 0.00 | 0 | 0.00 | 0 | 0.00 | 0 | 0.00 |
| Gas Leaks and Flaresa | 0 | 0.0 | 0 | 0.00 | 0 | 0.00 | 0 | 0.00 | 0 | 0.00 |
| Fertilizer Manufacture | 0 | 0.0 | 0 | 0.00 | 2 | 0.05 | 0 | 0.00 | 0 | 0.00 |
| N2O, NOx, CO2 From Fertilizer | 0 | 0.0 | 0 | 0.00 | 327 | 7.41 | 0 | 0.00 | 0 | 0.00 |
| Feedstock Recovery | 0 | 0.0 | 1 | 0.02 | 0 | 0.00 | 0 | 0.00 | 0 | 0.00 |
| Feedstock Transmission | 0 | 0.0 | 0 | 0.00 | 1 | 0.02 | 0 | 0.00 | 0 | 0.00 |
| Fuel Production | 4 | 0.1 | 3 | 0.07 | 10 | 0.20 | 0 | 0.00 | 0 | 0.00 |
| Sequestration | 0 | 0.0 | 0 | 0.00 | 0 | 0.00 | 0 | 0.00 | 0 | 0.00 |
| Fuel Distribution | 0 | 0.0 | 1 | 0.01 | 1 | 0.02 | 0 | 0.00 | 1 | 0.02 |
| Compression or Liquefaction | 0 | 0.0 | 0 | 0.00 | 0 | 0.00 | 1 | 0.02 | 0 | 0.00 |
| Subtotal | 4 | 0.1 | 5 | 0.10 | 341 | 7.70 | 1 | 0.02 | 1 | 0.02 |
| Vehicleb,c,d | 70 | 1.6 | 70 | 1.60 | 70 | 1.60 | 70 | 1.60 | 70 | 1.60 |
| Total | 74 | 1.7 | 75 | 1.70 | 411 | 9.30 | 71 | 1.62 | 71 | 1.62 |
| aAssumes that
flared gas is burned completely to CO2 and water vapor
with no methane, nonmethane organic components, carbon monoxide, NOx,
or N2O. bDecision Analysis Corporation, “Measurement of Emissions: Greenhouse Gas Estimates for Alternative Transportation Fuels,” unpublished final report prepared for the Energy Information Administration (Vienna, VA, December 1995). cGreenhouse gas (GHG) emission values from vehicle end-use are revised. dThe total GHG emission values are revised because vehicle end-use values are revised. CO2 = Carbon dioxide. LPG = Liquefied petroleum gases. mg = Milligrams. mmol = Millimoles. N2O = Nitrous oxide. NOx = Nitrogen oxides. VMT = Vehicle mile traveled. Notes: Gasoline refers to unleaded gasoline in this report. • Table was derived using a vehicle with gasoline efficiency of 30 miles per gallon. • Emissions from manufacturing the vehicles are not included. • Nitrogen oxides include primarily nitric oxide and nitrogen dioxide. One mole of a gas is equal to the amount of substance that contains as many elementary units (6.023 x 1023 molecules or atoms) as there are atoms in 12 grams of carbon-12. Normally, emissions are reported in grams per VMT. However, reporting in moles is preferable because GHG heat absorption is directly related to the number of molecules of a gas. Sources: Derived from GHG emissions spreadsheet provided to the Energy Information Administration, July 1994. Spreadsheet is an unpublished revision of Argonne National Laboratory, Center for Transportation Research, Emissions of Greenhouse Gases From the Use of Transportation Fuels and Electricity, ANL/ESD/TM-22, prepared by Dr. Mark Delucchi, Vol. 1 (Argonne, IL, November 1991) and Vol. 2 (Argonne, IL, November 1993). Also see Energy Information Administration, Alternatives to Traditional Transportation Fuels 1993, EIA/DOE-0585(93) (Washington, DC, January 1995). |
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| Table 11. Fuel Cycle Carbon Monoxide Emissions per Vehicle Mile Traveled (Milligrams and Millimoles) | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Fuel Cycle Stage | Gasoline | Methanol From Natural Gas | Ethanol From Corn | Compressed Natural Gas | LPG From Oil and Gas | |||||
| mg/ VMT |
mmol/ VMT |
mg/ VMT |
mmol/ VMT |
mg/ VMT |
mmol/ VMT |
mg/ VMT |
mmol/ VMT |
mg/ VMT |
mmol/ VMT |
|
| CO2 From Natural Gas Wells | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 |
| Gas Leaks and Flaresa | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 |
| Fertilizer Manufacture | 0 | 0.0 | 0 | 0.0 | 119 | 4.3 | 0 | 0.0 | 0 | 0.0 |
| N2O, NOx, CO2 From Fertilizer | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 |
| Feedstock Recovery | 138 | 4.9 | 65 | 2.3 | -2,211 | -79.0 | 43 | 1.5 | 62 | 2.2 |
| Feedstock Transmission | 21 | 0.8 | 17 | 0.6 | 52 | 1.9 | 0 | 0.0 | 5 | 0.2 |
| Fuel Production | 75 | 2.7 | 9 | 0.3 | 218 | 7.8 | 2 | 0.1 | 14 | 0.5 |
| Sequestration | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 |
| Fuel Distribution | 16 | 0.6 | 69 | 2.5 | 54 | 1.9 | 25 | 0.9 | 19 | 0.7 |
| Compression or Liquefaction | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 7 | 0.3 | 0 | 0.0 |
| Subtotal | 250 | 9.0 | 160 | 5.7 | -1,768 | -63.2 | 77 | 2.8 | 100 | 3.6 |
| Vehicleb,c,d | 9,000 | 321.4 | 9,000 | 321.4 | 9,000 | 321.4 | 9,000 | 321.4 | 9,000 | 321.4 |
| Total | 9,250 | 330.4 | 9,160 | 327.1 | 7,232 | 258.3 | 9,077 | 324.2 | 9,100 | 325.0 |
| aAssumes that
flared gas is burned completely to CO2 and water vapor
with no methane, nonmethane organic components, carbon monoxide, NOx,
or N2O. bDecision Analysis Corporation, “Measurement of Emissions: Greenhouse Gas Estimates for Alternative Transportation Fuels,” unpublished final report prepared for the Energy Information Administration (Vienna, VA, December 1995). cGreenhouse gas (GHG) emission values from vehicle end-use are revised. dThe total GHG emission values are revised because vehicle end-use values are revised. CO2 = Carbon dioxide. LPG = Liquefied petroleum gases. mg = Milligrams. mmol = Millimoles. N2O = Nitrous oxide. NOx = Nitrogen oxides. VMT = Vehicle mile traveled. Notes: Gasoline refers to unleaded gasoline in this report. • Table was derived using a vehicle with gasoline efficiency of 30 miles per gallon. • Emissions from manufacturing the vehicles are not included. • Nitrogen oxides include primarily nitric oxide and nitrogen dioxide. One mole of a gas is equal to the amount of substance that contains as many elementary units (6.023 x 1023 molecules or atoms) as there are atoms in 12 grams of carbon-12. Normally, emissions are reported in grams per VMT. However, reporting in moles is preferable because GHG heat absorption is directly related to the number of molecules of a gas. Sources: Derived from GHG emissions spreadsheet provided to the Energy Information Administration, July 1994. Spreadsheet is an unpublished revision of Argonne National Laboratory, Center for Transportation Research, Emissions of Greenhouse Gases From the Use of Transportation Fuels and Electricity, ANL/ESD/TM-22, prepared by Dr. Mark Delucchi, Vol. 1 (Argonne, IL, November 1991) and Vol. 2 (Argonne, IL, November 1993). Also see Energy Information Administration, Alternatives to Traditional Transportation Fuels 1993, EIA/DOE-0585(93) (Washington, DC, January 1995). |
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| Table 12. Fuel Cycle Nitrogen Oxides Emissions per Vehicle Mile Traveled (Milligrams and Millimoles) | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Fuel Cycle Stage | Gasoline | Methanol From Natural Gas | Ethanol From Corn | Compressed Natural Gas | LPG From Oil and Gas | |||||
| mg/ VMT |
mmol/ VMT |
mg/ VMT |
mmol/ VMT |
mg/ VMT |
mmol/ VMT |
mg/ VMT |
mmol/ VMT |
mg/ VMT |
mmol/ VMT |
|
| CO2 From Natural Gas Wells | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 |
| Gas Leaks and Flaresa | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 |
| Fertilizer Manufacture | 0 | 0.0 | 0 | 0.0 | 476 | 12.5 | 0 | 0.0 | 0 | 0.0 |
| N2O, NOx, CO2 From Fertilizer | 0 | 0.0 | 0 | 0.0 | 210 | 5.5 | 0 | 0.0 | 0 | 0.0 |
| Feedstock Recovery | 38 | 1.0 | 26 | 0.7 | 45 | 1.2 | 13 | 0.3 | 18 | 0.5 |
| Feedstock Transmission | 52 | 1.4 | 37 | 1.0 | 57 | 1.5 | 0 | 0.0 | 13 | 0.3 |
| Fuel Production | 90 | 2.4 | 380 | 10.0 | 560 | 14.7 | 6 | 0.2 | 16 | 0.4 |
| Sequestration | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 |
| Fuel Distribution | 22 | 0.6 | 130 | 3.4 | 70 | 1.8 | 54 | 1.4 | 23 | 0.6 |
| Compression or Liquefaction | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 45 | 1.2 | 0 | 0.0 |
| Subtotal | 202 | 5.4 | 573 | 15.1 | 1,418 | 37.2 | 118 | 3.1 | 70 | 1.8 |
| Vehicleb,c,d | 800 | 21.1 | 800 | 21.1 | 800 | 21.1 | 800 | 21.1 | 800 | 21.1 |
| Total | 1,002 | 26.5 | 1,373 | 36.2 | 2,218 | 58.3 | 918 | 24.2 | 870 | 22.9 |
| aAssumes that
flared gas is burned completely to CO2 and water vapor
with no methane, nonmethane organic components, carbon monoxide, NOx,
or N2O. bDecision Analysis Corporation, “Measurement of Emissions: Greenhouse Gas Estimates for Alternative Transportation Fuels,” unpublished final report prepared for the Energy Information Administration (Vienna, VA, December 1995). cGreenhouse gas (GHG) emission values from vehicle end-use are revised. dThe total GHG emission values are revised because vehicle end-use values are revised. CO2 = Carbon dioxide. LPG = Liquefied petroleum gases. mg = Milligrams. mmol = Millimoles. N2O = Nitrous oxide. NOx = Nitrogen oxides. VMT = Vehicle mile traveled. Notes: Gasoline refers to unleaded gasoline in this report. • Table was derived using a vehicle with gasoline efficiency of 30 miles per gallon. • Emissions from manufacturing the vehicles are not included. • Nitrogen oxides include primarily nitric oxide and nitrogen dioxide. One mole of a gas is equal to the amount of substance that contains as many elementary units (6.023 x 1023 molecules or atoms) as there are atoms in 12 grams of carbon-12. Normally, emissions are reported in grams per VMT. However, reporting in moles is preferable because GHG heat absorption is directly related to the number of molecules of a gas. Sources: Derived from GHG emissions spreadsheet provided to the Energy Information Administration, July 1994. Spreadsheet is an unpublished revision of Argonne National Laboratory, Center for Transportation Research, Emissions of Greenhouse Gases From the Use of Transportation Fuels and Electricity, ANL/ESD/TM-22, prepared by Dr. Mark Delucchi, Vol. 1 (Argonne, IL, November 1991) and Vol. 2 (Argonne, IL, November 1993). Also see Energy Information Administration, Alternatives to Traditional Transportation Fuels 1993, EIA/DOE-0585(93) (Washington, DC, January 1995). |
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Proceed to Appendix A