Life-cycle environmental and economic assessment of sewage sludge treatment in China

• LCA and LCC are used to assess the sewage sludge treatment in China.
• Anaerobic digestion is a suitable alternative for sewage sludge treatment.
• Landfill process had the highest environmental burden.
• The overall environmental burden was mainly generated from Hg and Pb emissions.
• Energy recovery can significantly reduce both environmental and economic burden.

A cost-combined life-cycle assessment was conducted to estimate the environmental and economic burdens of 13 sewage sludge-treatment scenarios in China. Results showed that anaerobic digestion was a suitable alternative to reduce both environmental and economic burdens because this approach reduced dry mass volume and applied energy recovery. Landfill and incineration technologies had the highest and lowest environmental burdens, respectively. Direct heavy metal emissions generated from landfill and incineration processes contributed significantly to human toxicity and marine ecotoxicity. However, energy recovery from the landfill and incineration stages was important to reduce both environmental and economic burdens. This study indicated that a sewage sludge-treatment scenario with anaerobic digestion, dewatering, and incineration technologies was the most environmentally and economically suitable method to treat sewage sludge because of energy recovery. All new sewage treatment plants should be constructed to operate according to this method, and existing plants should be retrofitted.