Cuihong Song

Abstract The wastewater sector is now increasingly targeting fugitive CH4 and N2O emissions. National inventory reports (NIRs) are central to tracking these non-CO2 emissions, yet the extent to which NIRs capture sector-wide wastewater emissions remain unclear due to inconsistent accounting methodologies, complex systems and large fluctuations across regions and time.

National greenhouse gas inventories systematically undercount methane and nitrous oxide emissions from wastewater due to outdated methods and incomplete coverage. Addressing these discrepancies is essential to strengthen transparency in global climate efforts and improving the effectiveness of national mitigation strategies. Recommendations for policy Expand inventory coverage to include all wastewater pathways, including septic systems, effluent discharges and decentralized systems.

Abstract Population growth and urbanization are driving the demand for centralized wastewater treatment, a primary source of N2O and CH4 emissions. We have conducted the first comprehensive assessment of CH4, N2O and NH3 emissions across diurnal, day-to-day and seasonal scales at 96 US water resource recovery facilities (WRRFs) that collectively treat 9% of US centralized wastewater. Facility-level emissions were scaled to the national level using a probabilistic approach.