Anaerobic co-digestion of coffee waste and sewage sludge

摘要

The feasibility of the anaerobic co-digestion of coffee solid waste and sewage sludge was assessed. Five different solid wastes with different chemical properties were studied in mesophilic batch assays, providing basic data on the methane production, reduction of total and volatile solids and hydrolysis rate constant. Most of the wastes had a methane yield of 0.24--0.28 m~3 CH_(4(STP))/kg VS_(initial) and 76-89 percent of the theoretical methane yield was achieved. Reduction of 50-73 percent in total solids and 75-80 percent in volatile solids were obtained and the hydrolysis rate constants were in the range of 0.035-0.063 d~(-1). One of the solid wastes, composed of 100 percent barley, achieved a methane yield of 0.02 m~3 CH_(4(STP))/kg VS_(initial) reductions of 31 percent in total solids, 40 percent in volatile solids and achieved only 11 percent of the theoretical methane yield. However, this waste presented the highest hydrolysis rate constant. Considering all the wastes, an inverse linear correlation was obtained between methane yield and the hydrolysis rate constant, suggesting that hydrolysis was not the limiting factor in the anaerobic biodegradability of this type of waste.