High spatial-temporal resolution mapping reveals hotspots of non-CO ₂ emissions from wastewater treatment plants in China

Emissions of non-CO2 greenhouse gases, represented by CH4 and N2O, are critical drivers of climate change. In China, the wastewater treatment sector ranks as the fourth-largest source of CH4 and N2O emissions. Hence, developing high–spatiotemporal-resolution inventories of CH4 and N2O emissions from the wastewater treatment sector is a necessary prerequisite for China to achieve its non-CO2 greenhouse-gas mitigation targets. This study develops a 0.1°×0.1° spatial resolution inventory of CH4 and N2O emissions from wastewater treatment plants across China spanning the period 2000-2024. Using an integrated approach combining top-down and bottom-up methodologies, the inventory establishes a refined emission factor database that distinguishes among technical processes and wastewater types. The results show that from 2000 to 2024, the non-CO2 greenhouse gas emissions of China's wastewater treatment plants increased exhibited a general increasing trend until 2015, followed by a decline thereafter. Emission hotspots have expanded from the eastern region to the central region, with top 10% of the wastewater treatment plants accounting for over 60% of total emissions. Our datasets provide a scientific basis for region-specific emission-reduction policy design.