3.6 Landfills
The point source emissions in the EPA’s Landfill dataset includes CO and 28 HAPs, as shown in Table 3.5. This set of pollutants was included in the 1999 NEI, and we continue to use the same set of pollutants each year for a consistent time series. To estimate emissions, we used the 2023 methane emissions reported by landfill operators in compliance with Subpart HH of the Greenhouse Gas Reporting Program (GHGRP) as a “surrogate” activity indicator. We converted the methane as reported in Mg CO2 equivalent to Mg as actual methane emitted by dividing by 23 (the Global Warming Potential of methane believed to be used in the version of the 2023 GHGRP facility inventory) to get Mg methane emitted and then multiplied by 1.1023 to get tons methane emitted3. We created emission factors for CO and the 28 HAPs on a per ton of methane emitted basis using the default concentrations (ppmv) in AP-42 Section 2.4 (final section dated Jan 1998), Table 2.4-1. The concentrations for toluene and benzene were taken from Table 2.4-2 of AP-42, for the case of “no or unknown” co-disposal history. Per Equation 4 of that AP-42 section, \(\text{M}_{p} = \text{Q}_{p} \times \text{MW}_{p} \times constant(k)\) (at any given temperature). Writing this equation twice, for the mass of any pollutant “P” and for methane (CH4), and dividing Mp by MCH4 yields:
\[\begin{equation} \frac{\text{M}_{p}}{\text{M}_{\text{CH}_{4}}} = \frac{\big(\text{Q}_{p} \times \text{MW}_{p} \times \text{k}\big)} {\big(\text{Q}_{\text{CH}_{4}} \times \text{MW}_{\text{CH}_{4}} \times \text{k}\big)} = \frac{\text{Q}_{p}} {\text{Q}_{\text{CH}_{4}}} \times \frac{\text{MW}_{p}} {\text{MW}_{\text{CH}_{4}}} \tag{3.1} \end{equation}\]
in units of pounds pollutant “P” per pound CH4.
A rearrangement of Equation 3 of that AP-42 section provides \(\frac{\text{Q}_{p}}{\text{Q}_{CH4}} = 1.82 \times \frac{\text{C}_{p}}{1,000,000}\), where the 1.82 is based upon a default methane concentration of 55% (550,000 ppm). Plugging this expression for \(\frac{\text{Q}_{p}}{\text{Q}_{CH4}}\) into the first expression yields:
\[\begin{equation} \frac{\text{M}_{p}}{\text{M}_{\text{CH}_{4}}} = \big(1.82 \times \frac{\text{C}_{p}}{1,000,000}\big) \times \frac{\text{MW}_{p}} {\text{MW}_{\text{CH}_{4}}} \times 2000 \tag{3.2} \end{equation}\]
in units of pounds pollutant “P” per ton CH4.
\[\begin{equation} \frac{\text{M}_{p}}{\text{M}_{\text{CH}_{4}}} = \big(1.82 \times \frac{\text{C}_{p}}{1,000,000}\big) \times \frac{\text{MW}_{p}} {16} \times 2000 =\text{C}_{p} \times \frac{\text{MW}_{p}} {4395.6} \tag{3.3} \end{equation}\]
| Pollutant code | Pollutant description | MW | ppmv | MW x ppmv | lbs/Ton CH4 |
|---|---|---|---|---|---|
| 71556 | 1,1,1-Trichloroethane (methyl chloroform) | 133.41 | 0.48 | 64 | 0.015 |
| 79345 | 1,1,2,2-Tetrachloroethane | 167.85 | 1.1 | 1.9e+02 | 0.042 |
| 75343 | 1,1-Dichloroethane (ethylidene dichloride) | 98.97 | 2.3 | 2.3e+02 | 0.053 |
| 75354 | 1,1-Dichloroethene (vinylidene chloride) | 96.94 | 0.2 | 19 | 0.0044 |
| 107062 | 1,2-Dichloroethane (ethylene dichloride) | 98.96 | 0.41 | 41 | 0.0092 |
| 78875 | 1,2-Dichloropropane (propylene dichloride) | 112.99 | 0.18 | 20 | 0.0046 |
| 107131 | Acrylonitrile | 53.06 | 6.3 | 3.4e+02 | 0.076 |
| 71432 | Benzene | 78.11 | 1.9 | 1.5e+02 | 0.034 |
| 75150 | Carbon disulfide | 76.13 | 0.58 | 44 | 0.01 |
| CO | Carbon monoxide | 28.01 | 1.4e+02 | 3.9e+03 | 0.9 |
| 56235 | Carbon tetrachloride | 153.84 | 0.004 | 0.62 | 0.00014 |
| 463581 | Carbonyl sulfide | 60.07 | 0.49 | 29 | 0.0067 |
| 108907 | Chlorobenzene | 112.56 | 0.25 | 28 | 0.0064 |
| 75003 | Chloroethane (ethyl chloride) | 64.52 | 1.2 | 81 | 0.018 |
| 67663 | Chloroform | 119.39 | 0.03 | 3.6 | 0.00081 |
| 74873 | Chloromethane | 50.49 | 1.2 | 61 | 0.014 |
| 106467 | Dichlorobenzene | 147 | 0.21 | 31 | 0.007 |
| 75092 | Dichloromethane (methylene chloride) | 84.94 | 14 | 1.2e+03 | 0.28 |
| 100414 | Ethylbenzene | 106.16 | 4.6 | 4.9e+02 | 0.11 |
| 106934 | Ethylene dibromide | 187.88 | 0.001 | 0.19 | 4e-05 |
| 110543 | Hexane | 86.18 | 6.6 | 5.7e+02 | 0.13 |
| 7783064 | Hydrogen sulfide | 34.08 | 36 | 1.2e+03 | 0.28 |
| 7439976 | Mercury (total) | 200.61 | 0.00029 | 0.059 | 1e-05 |
| 108101 | Methyl isobutyl ketone | 100.16 | 1.9 | 1.9e+02 | 0.043 |
| 127184 | Perchloroethylene (tetrachloroethylene) | 165.83 | 3.7 | 6.2e+02 | 0.14 |
| 108883 | Toluene | 92.13 | 39 | 3.6e+03 | 0.82 |
| 79016 | Trichloroethylene (trichloroethene) | 131.4 | 2.8 | 3.7e+02 | 0.084 |
| 75014 | Vinyl chloride | 62.5 | 7.3 | 4.6e+02 | 0.1 |
| 1330207 | Xylenes | 106.16 | 12 | 1.3e+03 | 0.29 |
For more information on CO2 equivalent and global warming potential, please refer to EPA’s page “Understanding Global Warming Potentials”.↩︎