Environmental and Economic Implication of Implementation Scale of Sewage Sludge Recycling Systems Considering Carbon Trading Price

Abstract

With China’s ongoing economic development and increasing emphasis on environmental protection, the number and treatment capacity of sewage plants is increasing annually. Simultaneously, sludge production is increasing. In recent years, researchers have investigated various approaches to the environmental and economic analysis of sludge treatment and recycling systems (STRS). These investigations did not take the universal law of different capacities for environmental impact and STRS economics into account. The aim of this study was to analyze the scale effect of STRS with different technologies (i.e., incineration, aerobic composting, used in material (brick), anaerobic digestion) on the environment and economy. Moreover, the cost–benefit impact of introducing a carbon- trading mechanism into the STRS to achieve carbon neutrality was analyzed. After reducing carbon emissions through by-products of STRS, the carbon emission quota can be sold, which will generate income. The results show that the break-even scales for incineration, anaerobic composting, used in building material (brick), and anaerobic digestion are 54,899, 6707, 48,775, and 4425 t/y, respectively. The break-even scale of each system decreased after the introduction of the carbon trading system into the STRS. These findings could provide critical technical information for superior decision-making in sewage sludge recycling systems.