Abstract: Municipal sludge incineration is the development direction of sludge reduction in China, which produces 40-50% incinerated sewage sludge ash（ISSA）.The ISSA is rich in silicon, aluminum and phosphorus. How to realize the near-zero landfill and high-value utilization of ISSA is a research hot-spot of resource recycling at home and abroad. In this paper, the material flow method and life cycle assessment method are combined to analyze the environmental impact of three disposal scenarios, including ISSA to landfill, ISSA instead of clay, phosphorus recovery from ISSA and then residue instead of clay. The cost-benefit method compares the economic benefits of the three disposal scenarios. The results show that ISSA utilization is superior to ISSA to landfill in abiotic depletion potential elements, acidification potential, eutrophication potential, freshwater aquatic ecotoxicity, global warming potential, photo hem ozone creation potential. In addition, phosphorus recovery from ISSA and then residue instead of clay is the best disposal scenarios with a net income of 141.21 yuan/ton ISSA. If the disposal path is extended to all sewage treatment plants in China, 262,600 tons of phosphorus can be extracted and 2,092,300 tons of struvite can be produced each year.

Key words: incinerated sewage sludge ash, disposal modes, phosphorus recovery, life cycle environmental assessment, economic benefits