Production of Biomethane from Cafeteria, Vegetable and Fruit Wastes by Anaerobic Co-Digestion Process

Abstract

Alleviate energy crisis and global climate change, the world is need of a green, efficient, carbon-neutral renewable energy source to replace fossil fuels. This study was designed to determine the optimal mixing ratio of cafeteria, vegetable and fruit wastes in biogas production and methane yields using batch anaerobic digesters at mesophilic (25 to 34℃) temperature. The mixing ratio used were CW:VW:FW (0.5:1.0:1.5, 1.0:1.5:0.5, 1.5:0.5:1.0 and 1.0:1.0:1.0) for cafeteria waste (CW), vegetable waste (VW) and fruit waste (FW) respectively. The fermentation was carried out in 200 L polypropylene digesters. The results showed that the co-digestion significantly affected the biogas production rate. At four mixing ratio tested, after 35 days of digestion, the biogas yield was determined to be CW:VW:FW (0.5:1.0:1.5, 1.0:1.5:0.5, 1.5:0.5:1.0 and 1.0:1.0:1.0) were 13.38, 15.85, 17.03 and 19.43 L/day, respectively. The cumulative average biogas productions from CW:VW:FW (0.5:1.0:1.5, 1.0:1.5:0.5, 1.5:0.5:1.0 and 1.0:1.0:1.0) were 225, 279, 305 and 332 L/day, respectively. The biogas yields obtained in the work for the cafeteria (CW), vegetable (VW) and fruit wastes (FW) mixture were in the order of (1.0:1.0:1.0 > 1.5:0.5:1.0 > 1.0:1.5:0.5 > 0.5:1.0:1.5). The higher methane contents and yields were obtained from the CW:VW:FW (1.0:1.0:1.0) mixture ratio than those from the CW:VW:FW (1.5:0.5:1.0, 1.0:1.5:0.5, and 0.5:1.0:1.5). Thus, optimum mixing ratio suggested by the study which gave maximum yields within 35 day hydraulic retention time without inoculums added. 