Predicting sludge generation patterns and carbon reduction potential under Shared Socioeconomic Pathways

Abstract

Sludge management accounts for a large share of economic costs and energy consumption in wastewater treatment and has become an important challenge for urban sustainability. Accurately predicting regional sludge generation by incorporating spatial characteristics to find carbon reduction potential can help improve the sustainability of wastewater treatment and formulate tailored mitigation strategies. This is especially true in China, which along with the world's largest wastewater treatment capacity, also faces rapid growth in sludge generation, insufficient disposal capacity, and low recycling rates. In this study, data from 3,495 wastewater treatment plants were used to screen sludge driving factors in 338 Chinese cities, and a random forest regression model was used to predict future sludge generation and associated carbon emissions at the provincial level under Shared Socioeconomic Pathways. The results showed that GDP, built-up area, and carbon content of foods had relatively high q-values (above 0.5). Indicating that economic development, urban form, and food consumption were the major factors influencing sludge generation. By 2060, total sludge generation in China is expected to be between 195% and 241% of the 2017 total in the five SSP scenarios. Improved disposal methods should be implemented to reduce carbon emissions in regions that have stable sludge growth, while fast-developing areas should focus on sludge reduction. In Central and Western China, it may be possible to control sludge generation at the source given expected changes in dietary structure and urban compact development change, while in Eastern China greater use of anaerobic digestion and sludge-to-resource treatment may be more effective. Combining anaerobic digestion and low carbon disposal methods could reduce about 50 Mts GHG emissions in China by 2060.