Table 1 Contribution of domestic wastewater treatment emissions to national US emissions

From: Comprehensive assessment of the contribution of wastewater treatment to urban greenhouse gas and ammonia emissions

Gas

Total domestic emissions (kt)

EPA-estimated domestic WRRF emissions (kt)

EPA-estimated domestic WRRF emissions (%)

This study domestic WRRF emissions (kt)

This study domestic WRRF emissions (%)e

CH4

25,084a

270a

1.1

639

2.5

N2O

1,471a

61a,c

4.1

119

8.1

NH3

5,482b

<1d

<0.1d

87

1.6

  1. aObtained from ref. 10. bObtained from US EPA National Emissions Inventory (NEI; accessed 26 July 2023 at https://www.epa.gov/air-emissions-inventories/2020-nei-supporting-data-and-summaries). cExcludes emissions from wastewater effluent and septic systems. dCentralized wastewater is not reported as a separate category in the NEI database, so we used an EF of 0.169 lbNH3 per million gallons, taken from the NEI documentation33 in table II-5 of ref. 50, assuming 34,000 MGD (1.24 × 1013 gallons yr−1)24. eAssuming that the national emission estimate is correct and that the sector allocation is incorrect.
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