Energy, environment and economy assessment of sewage sludge incineration technologies in China

Sludge incineration attracts increasing interests in China. Different sludge incineration modes, incinerator types, auxiliary fuel and sludge drying heat sources can cause various energy, environmental and economic performances. In this study, seven sludge incineration technologies (i.e., rotary kiln incineration with coal or natural gas fuel, fluidized bed incineration with natural gas or biomass fuel, co-incineration in coal-fired power plant (CFPP), and co-incineration in waste-incineration power plan (WIPP) by electric drying or steam drying) were evaluated and compared via energy flow analysis (EFA), life cycle assessment (LCA), and life cycle cost (LCC) methods. EFA results show that energy utilization efficiency of individual incineration without full utilization of waste heat is lower than 28%. LCA results show that comprehensive environmental indicator of coal and natural gas are approximately 100 times as large as biomass. For different drying heat sources, steam instead of electricity shows superior environmental impact. LCC results demonstrate that individual incineration technologies are 2–4 times that of co-incineration technologies in investment cost. The results of decision alternative ratia evaluation showed that co-incineration in CFPP is the best in seven technologies, followed by co-incineration in WIPP with steam drying.