Unlocking sludge co-firing synergies between thermal power and wastewater treatment plants

Co-firing municipal wastewater treatment plant (MWWTP) sludge in thermal-fired power plants (TFPPs) offers a low-carbon circular strategy. However, its adoption is constrained by spatio-temporal supply–demand mismatches and economic feasibility. Here we show that an optimized, plant-level monthly allocation framework can overcome these barriers, powered by a high-resolution database of 5,218 MWWTPs and 1,990 TFPPs across China. We find that surplus sludge from 3,735 MWWTPs (~87% capacity) can stably substitute coal on a monthly basis across 421 qualified TFPPs. This symbiotic network reduces total sludge volume by 79% (95% CI 55–88%) and mitigates 15.25 (10.53–17.39) MtCO₂eq annually (50% of MWWTP emissions), while yielding median incremental profits of 369.41 (4.18–1,250.46) million CNY yr^‒1. Scenario analysis reveals that rising fuel prices can amplify environmental and economic benefits by 11% and 135%. Crucially, despite a shrinking coal-power sector under future energy transitions, long-term co-firing network resilience is sustained through a 35–67% expansion in collaborative TFPPs. These insights provide a scalable framework for implementing cross-sectoral circular strategies tailored to regional sustainability.