Spatio-temporal distribution of sewage sludge, its methane production potential, and a greenhouse gas emissions analysis

With ongoing economic development and population growth in China, large quantities of wastewater are discharged and substantial amounts of sewage sludge are generated, which is a potential biomass resource for methane production. This study used data from statistics yearbooks and literatures to evaluate the spatio-temporal distribution of sludge generation, potential and distribution of methane production from sludge, and the potential of greenhouse gas (GHG) emissions reduction (PGER) from sludge treatment and disposal in provinces in mainland China. The results showed that a total of 6.03 Mt of dry solids in 2015. The eastern part of the country produced more sludge than that the western part. The standard coal equivalence of sludge was 3.5 Mt, ranged from 0.7 to 399.8 Kt, among the 31 provinces of mainland China. Total sludge could produce 1.27 billion m(3) of methane per year through anaerobic digestion (AD). The distribution of methane density exhibited that the east part was higher than the west part in China. The GHG emissions totaled 18.82 Mt CO2-eq as a baseline for the current sludge disposal methods without AD technology. The PGER was 10.77 Mt CO2-eq for the sludge disposal routes with AD technology. The sludge disposal for the project route of building material exhibited the highest PGER of 4.24 Mt CO2-eq among the disposal methods. As the least GHG emissions method, sludge treated by AD and the residue disposed for land using as fertilizer should be recommended. Our findings provide a sludge disposal reference for the government and industries. For further study, it is suggested to take the co-digestion technology into consideration for sewage sludge to produce methane, which would perform a higher methane production and GHG emissions reduction potential. (C) 2019 Elsevier Ltd. All rights reserved.