A review-based estimation of GHG emissions of China's wastewater management system.

Under China's "Dual Carbon Goal", the wastewater treatment system plays a crucial role in the country's efforts to reduce greenhouse gas (GHG) emissions. However, a lack of baseline emissions data poses challenges for decarbonization efforts. This study aims to profile and diagnose the GHG emissions of China's entire wastewater system and identify key contributing factors. Our findings show that China's wastewater system, including wastewater treatment plants (WWTPs) and septic tanks, is responsible for significant emissions, with baseline estimates at 108.26 ± 47.37 Mt CO2-eq/a. Septic tanks and WWTPs emerged as the major GHG hotspots, contributing the most to the total emissions. This study highlights the variability in emission results from previous literature, stressing the need for consistent accounting methods and scientific emission factors. Additionally, current on-site monitoring practices in China show gaps, which hinder the accurate determination of baseline emissions. To guide future emission reduction strategies, regulatory frameworks and improved monitoring practices are recommended for the wastewater sector in China.