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A comprehensive study for characteristics, acidogenic fermentation, and anaerobic digestion of source separated organics

Bazyar Lakeh, A.A., Azizi, A., Hosseini Koupaie, E., Bekmuradov, V., Hafez, H., Elbeshbishy, E.
Journal of cleaner production 2019 v.228 pp. 73-85
anaerobic digestion, biogas, chemical oxygen demand, cost benefit analysis, eating habits, fermentation, food waste, hydrolysis, income, methane, methane production, operating costs, summer, total suspended solids, volatile fatty acids, winter
In this research, the physiochemical characteristics of source separated organics (SSO) throughout a long-term period, along with their possible effects on anaerobic digestion (AD), acidogenic fermentation, and hydrolysis processes were investigated. Seasonal characteristics of SSO revealed significant differences in some factors demonstrating that eating habits, waste handling, and collection techniques would lead to the variation in SSO characteristics. The SSO collected during the summer months revealed a significantly higher yield for soluble COD based on the mass of volatile suspended solids (VSS) (428 mg/g-VSS) and volatile fatty acids (VFAs) production (292 mg COD VFAs/g-VSS) compared to those of the winter samples. The results revealed that 65–68% of the produced SCOD during the acidogenic fermentation process belonged to VFAs. It was also revealed that 85% of the VFAs was produced during the first two days of the fermentation process. The mesophilic batch AD process achieved based on the mass of volatile solids (VS) an average methane yield of 555 mL CH4/g VS, which was significantly higher than the range of 350–480 mL CH4/g-VS reported for food waste in the literature. Considering the results of the present study, the SSO has a significant potential to produce biomethane and VFAs at the industrial scale. The cost-benefit analysis of a full-scale AD plant with a capacity of processing 75,000 tonnes SSO/year revealed that the revenue from selling the SSO-derived CH4 (∼400,000 $/year) could compensate for about 20% of the operating cost of the plant.