Spatiotemporal pattern of greenhouse gas emissions in China's wastewater sector and pathways towards carbon neutrality

Greenhouse gas (GHG) emissions from the wastewater sector are a major contributor to the overall GHG emissions of all countries, however, there is currently a lack of global, national-scale, detailed spatiotemporal emission data. In this study we elaborated dynamic plant-resolved emission factor values based on the case-specific operating parameters of each municipal wastewater treatment plant (WWTP) and the associated sewers and sludge disposal utilities in China, contrasting with previous estimations that typically focused on WWTP operation without differentiating their spatiotemporal discrepancies. We demonstrate here that China's municipal wastewater industry generated 53.0 MtCO2e in total GHG emissions in 2019, with the northern and southern areas exhibiting noticeably higher GHG intensities. Due to improved wastewater treatment, the national average wastewater GHG intensity grew by 17.2% between 2009 and 2019, although it is anticipated that the intensity will begin to fall starting in 2020 at rates dependent on the chosen treatment methods. A net-zero emission by the entire sector may be achieved as early as 2044 with continually increasing decarbonized energy and a progressive shift to resource-oriented operations, compared with just a 23.7% decrease by 2050 under the baseline scenario. Joint efforts at the scientific, economic and policy level will be required to make this happen. This study may serve as a roadmap for developing carbon-neutral wastewater management policies and technologies in China and the rest of the globe.