Sustainable management strategies for low-organic matter sludge from a life cycle perspective

Abstract

Sludge quality is a critical factor influencing the economic and environmental performance of treatment and disposal processes. In many regions, sludge is typically characterized by a low organic matter content. Consequently, the selection of sludge treatment and disposal routes should be tailored to the specific characteristics of sludge in each region, considering its dual attributes of “resource” and “pollution”, and aiming to maximize environmental, economic, and social benefits. Using the current sludge treatment and disposal situation in Wuhan, China, this study conducted a quantitative assessment of carbon emissions, environmental risks, and economic benefits associated with several existing treatment and disposal routes from a life cycle perspective. The results suggest that for sludge characteristics with low organic matter content, co-incineration in coal-fired power plants or cement production processes is the most favorable option. Specifically, when the organic matter content of the sludge falls below approximately 40%, cement production is deemed the preferred process, whereas co-incineration with coal is favored when the organic matter content exceeds 40% but is less than 50%. Owing to the relatively low organic matter and nutrient contents of sludge, optimization of existing anaerobic digestion and aerobic composting processes can be achieved through collaborative treatment with other solid wastes. Moreover, the prevailing carbon trading prices in the Chinese carbon market are relatively low and do not significantly impact the selection of current sludge treatment processes. This study aids in the development of sustainable management strategies for sludge characterized by low resource and pollution attributes in the future.

Graphical abstract