Toward Net-Zero Wastewater Sludge Management in China: Life Cycle and Multidimensional Analysis of Optimized Thermal Treatment Pathways

China’s rapid urbanization boosts sewage sludge production, making sustainable, low-carbon management critical for carbon neutrality goals. To address the critical need for sustainable sludge management, this study develops an energy-normalized life cycle assessment model to evaluate sewage sludge treatment technologies from integrated energy, environmental, and economic perspectives. For the first time, provincial-level carbon-reduction potentials are estimated under this multidimensional framework. Results demonstrate that an integrated anaerobic digestion-pyrolysis system achieves net-negative carbon emissions, reducing cumulative provincial emissions by 269 million tonnes CO 2 —equivalent over 20 years compared to conventional incineration—equivalent to five times Singapore's total CO 2 emissions in 2024. The system also yields a net environmental benefit of –9.78 person-equivalents per tonne of dry sludge and an economic return of US$3.34 per tonne without subsidies. These findings identify anaerobic digestion coupled with pyrolysis as the optimal sustainable sludge management strategy, providing a methodological framework and policy-relevant insights into advancing net-zero carbon waste management in China and beyond.