High-solids fermentation of food wastes for biogas recovery by using horizontal anaerobic reactor

Abstract

The biogas recovery from food wastes by anaerobic digestion was considered to be a feasible way for waste treatment. The system performance of high-solid anaerobic digestion of canteen food wastes by a horizontal reactor (8l) was investigated in this study. The TS of the reaction system was kept at 15%. The results indicated that biogas remained stable at about 650 ml/gTS when the volumetric loading rate (VLR) increased from 2 gTS/l.d to 8 gTS/l.d; however, it decreased at the VLR of 11 gTS/l.d. It suggested that VLR of 8 gTS/l.d was the optimal rate for this horizontal anaerobic reactor. After the adjustment of the running operation, the reactor remained stable with the accumulative biogas yield of 484 ml/gTS. The concentration of soluble chemical oxygen demand, ammonia nitrogen, volatile fatty acid, and alkalinity sharply increased to 41 024 mg/l, 2711 mg/l, 16 366 mg/l, and 14 250 mg/l at day 65 which reflected at the instable stage of the reactor, respectively. The maximum values of amylase and protease enzyme occurred at the initial stage of the reaction system with 1.42 U/ml (day 10) and 1.53 × 10−3 U/ml (day 17), respectively. After that, the two enzymes remained stable.