Methodology
Overview
We created our Carbon Dioxide Emissions by Fuel table by using information in our Monthly Energy Review as well the U.S. Environmental Protection Agency’s (EPA) Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2021 and Greenhouse Gas Emissions Factor Hub. In this document, we outline the steps for creating the values shown in the table.
Step 1: Obtain emissions factors
Unless noted otherwise, we take the carbon dioxide (CO2) emissions factors in this table from Appendix Tables A-19, A-24, A-31, and A-215 of EPA’s Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2021. Factors are provided in terms of million metric tons of carbon per quadrillion British thermal units (quads), which is equivalent in value to kilograms of carbon per million British thermal units (MMBtu). To convert from carbon to CO2, we multiply this factor by 44/12, the weight ratio of CO2 to carbon.
Emissions factors for municipal solid waste, tire-derived fuels, and waste oil are not listed in the greenhouse gas inventory, so we collect them from EPA’s Greenhouse Gas Emissions Factor Hub. Other fuels have emissions factors listed in both the greenhouse gas inventory as well as the emissions factor hub. Occasionally, these factors differ from one another. In such cases, because the factors in the emissions factors hub aren’t always updated on a regular basis, we treat the factors presented in the greenhouse gas inventory as the official values.
We adjust the emissions factor for finished motor gasoline based on its ethanol content, which we explain in detail later in this document.
Step 2: Convert CO2 weights from kilograms to pounds
We use the weight ratio of 2.20462 pounds per kilogram to convert each fuel’s emissions factor from kilograms per MMBtu to pounds per British thermal units (Btu).
Step 3: Apply heat rates for fuels
We calculate emissions by mass (or volume) by multiplying the emissions factor of each fuel (in pounds per MMBtu) by its associated heat rate. We collect heat rates from Appendix A of our Monthly Energy Review. For petroleum products with heat rates expressed in terms of MMBtu per barrel, we divide this value by 42 to convert from barrels to gallons. Table 1 shows heat rates for each fuel.
| Fuel | Value | Units |
|---|---|---|
| For homes and businesses | ||
| Propane | 3.841 | MMBtu per barrel |
| Diesel and home heating fuel (distillate fuel oil) | 5.770 | MMBtu per barrel |
| Kerosene | 5.670 | MMBtu per barrel |
| Coal (all types) | 18.399 | MMBtu per short ton |
| Natural Gas | 1.037 | MMBtu per thousand cubic feet |
| Finished motor gasoline | 5.050 | MMBtu per barrel |
| Motor gasoline (not including fuel ethanol) | 5.222 | MMBtu per barrel |
| Residual heating fuel (businesses only) | 6.287 | MMBtu per barrel |
| Other transportation fuels | ||
| Jet fuel | 5.670 | MMBtu per barrel |
| Aviation gas | 5.048 | MMBtu per barrel |
| Industrial fuels and others not listed above | ||
| Petroleum coke | 6.135 | MMBtu per barrel |
| Nonfuel uses | ||
| Asphalt and road oil | 6.636 | MMBtu per barrel |
| Lubricants | 6.065 | MMBtu per barrel |
| Naphthas for petrochemical feedstock use | 5.248 | MMBtu per barrel |
| Other oils for petrochemical feedstock use | 5.825 | MMBtu per barrel |
| Special naphthas (solvents) | 5.248 | MMBtu per barrel |
| Waxes | 5.537 | MMBtu per barrel |
| Coals by type | ||
| Anthracite | 25.090 | MMBtu per short ton |
| Bituminous | 23.270 | MMBtu per short ton |
| Subbituminous | 17.490 | MMBtu per short ton |
| Lignite | 12.970 | MMBtu per short ton |
| Coke | 28.666 | MMBtu per short ton |
| Other fuels | ||
| Geothermal (steam) | NA | NA |
| Geothermal (binary cycle) | NA | NA |
| Municipal solid waste | 14.210 | MMBtu per short ton |
| Tire-derived fuel | 28.000 | MMBtu per short ton |
| Waste oil | 5.796 | MMBtu per barrel |
| Data source: U.S. Energy Information Administration Note: MMBtu = million British thermal units |
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Step 4: Convert CO2 weights from pounds to kilograms
We use the weight ratio of 2.20462 pounds per kilogram to convert each fuel’s emissions from kilograms to pounds per unit of mass (or volume).
Motor gasoline adjustments
This table adjusts the heat rate and carbon factor of motor gasoline to distinguish between finished motor gasoline, which contains some portion of fuel ethanol, and raw motor gasoline, which does not.
The carbon factor for raw motor gasoline, not taking into account fuel ethanol, appears in Table A-22 of EPA’s Inventory of U.S. Greenhouse Gas Emissions and Sinks. Finished motor gasoline contains a blend of both raw motor gasoline, which is emissive, and fuel ethanol, which we treat as non-emissive in this calculation.
We calculate the carbon factor of finished motor gasoline by weighting the carbon factor of raw motor gasoline by the annual share of raw motor gasoline present in finished motor gasoline on an energy basis (Table 2). Energy consumption values appear in Tables 3.6 and 10.3 of our Monthly Energy Review.
| Year | Motor gasoline supplied (trillion Btu) | Fuel ethanol, excluding denaturant, losses, and co-products (trillion Btu) | Percentage share of motor gasoline in finished motor gasoline | Percentage share of ethanol in finished motor gasoline |
|---|---|---|---|---|
| 2010 | 16,631.51 | 725.97 | 95.82% | 4.18% |
| 2011 | 16,175.04 | 753.99 | 95.55% | 4.45% |
| 2012 | 16,085.45 | 709.13 | 95.78% | 4.22% |
| 2013 | 16,332.11 | 711.24 | 95.83% | 4.17% |
| 2014 | 16,472.65 | 764.22 | 95.57% | 4.43% |
| 2015 | 16,941.49 | 788.34 | 95.55% | 4.45% |
| 2016 | 17,237.81 | 818.06 | 95.47% | 4.53% |
| 2017 | 17,201.35 | 844.34 | 95.32% | 4.68% |
| 2018 | 17,209.27 | 851.96 | 95.28% | 4.72% |
| 2019 | 17,166.23 | 831.94 | 95.38% | 4.62% |
| 2020 | 14,883.26 | 731.95 | 95.31% | 4.69% |
| 2021 | 16,249.54 | 786.48 | 95.38% | 4.62% |
| Data source: U.S. Energy Information Administration Btu = British thermal units |
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