Biogas Recovery and Waste Reduction from Kitchen Food Waste by Using Anaerobic Digestion

Abstract

Kitchen food waste is defined as food that is left over or wasted during the production, processing, distribution, procurement, preparation, and consumption processes. About 50% of all food waste is reportedly to originate from kitchens and since it can decompose, food waste is regarded as degradable kitchen waste. In Malaysia, about 15,000 tonnes per day kitchen food waste generated and has the potential to produce hazardous gases, leachate, air pollution from food decay and quickly expanding landfills. In this study, kitchen food waste was used to recover biogas using anaerobic digestion. Additionally, the volume of waste reduced was also investigated to prove that anaerobic digestion is not only to recover resources, but also to reduce waste generation. The anaerobic digestion was performed at pH value of pH6.8-7.2 and temperature 37^oC for 15 days. Two (2) different samples of kitchen waste were used namely, shallots and cabbage. The biogas recovery was determined using water displacement technique. Kitchen food waste was also characterized before and after anaerobic digestion in terms of total solids, volatile solids and pH value. It is found that the percentage of total solids for shallots and cabbage before anaerobic digestion were 19.9% and 16.8%, respectively, and the percentage of volatile solids before anaerobic digestion were 88.1% and 95.6%, respectively. After anaerobic digestion, the percentage of total solids for shallots and cabbage were 15.5% and 13.6%, respectively, and the percentage of volatile solids were 21.0% and 15.2%, respectively. This suggests that the total and volatile solids of shallots and cabbage were reduced with 22.11% and 19.5%, and 76.14% and 84.14%, respectively, after performing anaerobic digestion. While 168mL and 52mL of biogas can be recovered from shallots and cabbage, respectively, throughout 15 days anaerobic digestion. This shows that anaerobic digestion is not only to recover biogas but also to reduce waste.