With the acceleration of economic development and urbanization in China, sewage sludge generation has sharply increased. To maximize energy regeneration and resource recovery, it is crucial to analyze the environmental impact and sustainability of different sewage sludge recycling systems based on life cycle assessment. This study analyzed four sewage sludge recycling systems in China through life cycle assessment using the ReCipe method, namely aerobic composting, anaerobic digestion and biomass utilization, incineration, and heat utilization and using for building materials. In particular, the key pollution processes and pollutants in sewage sludge recycling systems were analyzed. The results demonstrated that aerobic composting is the most environmentally optimal scenario for reducing emissions and energy consumption. The lowest environmental impact and operating costs were achieved by making bricks and using them as building materials; this was the optimal scenario for sludge treatment and recycling. In contrast, incineration and heat utilization had the highest impact on health and marine toxicity. Anaerobic digestion and biomass utilization had the highest impact on climate change, terrestrial acidification, photochemical oxidant formation, and particulate matter formation. In the future, policy designers should prioritize building material creation for sludge treatment and recycling.
Environmental & economic life cycle assessment of current & future sewage sludge to energy technologies
