Co-digestion of Food Waste and Human Excreta for Biogas Production

Abstract

The ever increasing cost of fossil fuels and its attendant pollution menace has provided the pedigree to consider alternative sources of energy. An investigation was launched into the design and construction of an Anaerobic Digester system from locally available raw materials using local technology and the production of biogas from food wastes and Human excreta generated within a University campus. The experiment lasted for 60 days using a 40-liters laboratory scale anaerobic digester. The volume of gas generated from the mixture was 84,750cm3 and comprised of 58% CH4, 24% CO2, and 19% H2S and other impurities. The physico-chemistry of the feedstock in the digester revealed an initial drop in pH to more acidic range and a steady increase 4.52 – 6.10. The temperature remained relatively constant at mesophilic range: 22.0ºC– 30.5ºC throughout the study. The Carbon/Nitrogen (C/N) ratio of the feedstock before digestion was within 139:1. Population distributions of the microflora show aerobic and anaerobic bacteria to include Klebsiella spp, Bacillus spp, Escherichia coli, Clostridium spp and a methanogen of the genera Methanococcus. In most developing nations of Sub-Saharan Africa where biomass is abundant, and where biogas technology is in its infant stage, the anaerobic digestion system could be the much awaited solution.