Underestimation of Sector-Wide Methane Emissions from United States Wastewater Treatment.

ABSTRACT: An increasing percentage of US waste methane (CH₄) emissions come from wastewater treatment (10% in 1990 to 14% in 2019), although there are limited measurements across the sector, leading to large uncertainties in current inventories. We conducted the largest study of CH₄ emissions from US wastewater treatment, measuring 63 plants with average daily flows ranging from 4.2 × 10^-4 to 8.5 m³ s^-1 (<0.1 to 193 MGD), totaling 2% of the 62.5 billion gallons treated, nationally. We employed Bayesian inference to quantify facility-integrated emission rates with a mobile laboratory approach (1165 cross-plume transects). The median plant-averaged emission rate was 1.1 g CH₄ s^-1 (0.1-21.6 g CH₄ s^-1; 10th/90th percentiles; mean 7.9 g CH₄ s^-1), and the median emission factor was 3.4 × 10^-2 g CH₄ (g influent 5 day biochemical oxygen demand; BOD₅)^-1 [0.6-9.9 × 10^-2 g CH₄ (g BOD₅)^-1; 10th/90th percentiles; mean 5.7 × 10^-2 g CH₄ (g BOD₅)^-1]. Using a Monte Carlo-based scaling of measured emission factors, emissions from US centrally treated domestic wastewater are 1.9 (95% CI: 1.5-2.4) times greater than the current US EPA inventory (bias of 5.4 MMT CO₂-eq). With increasing urbanization and centralized treatment, efforts to identify and mitigate CH₄ emissions are needed.

SUBMITTER: Moore DP 

PROVIDER: S-EPMC10018768 | biostudies-literature | 2023 Mar

REPOSITORIES: biostudies-literature