UPGRADED BIOMETHANE PRODUCTION FROM PILOT SCALE CO-DIGESTION OF FOOD WASTE AS A RENEWABLE SOURCE OF FUEL FOR ELECTRICITY
Abstract
This project was conceived to utilize the mounting food and other solid organic wastes arising from the recent increase in students’ population in Kaduna Polytechnic campus for electricity generation. This study investigated the construction, operation and performance evaluation of a pilot-scale anaerobic biodigester for the production of Biomethane from the co-digestion of institutional food waste and cow dung. A high-density polyethylene biodigester was fabricated and operated under mesophilic conditions (32 – 38 oC) with a hydraulic retention time of 30 days. Food waste collected from Kaduna Polytechnic cafeterias was characterized through proximate and ultimate analyses before digestion. The prepared substrate consisted of food waste and cow dung mixed at an optimum carbon-to-nitrogen ratio of approximately 25:1and a total solids concentration of 8%. Raw biogas generated from the digestion process was upgraded a locally fabricated alkaline water-scrubbing system for carbon dioxide and hydrogen sulphide removal. Gas composition before and after purification was determined using a digital gas analyzer. The methane concentration increased from 58% in raw biogas to 92.4% after upgrading, while carbon dioxide decreased from 38% to 7.2% and hydrogen sulphide from 3% to 0.4%. The upgraded biometane successfully powered a modified 2.5 kVA generator, producing a stable electrical output of approximately 1.8 kW., which supplied electricity computers, lighting facilities and fans for about 6 hours daily. The system also demonstrated significant economic and environmental benefits through waste reduction, fossil fuel substitution, and greenhouse gas emission mitigation. The findings demonstrated that locally fabricated biomethane system provide a technically feasible, environmentally sustainable and economically attractive solution for institutional organic waste management and decentralized electricity generation in developing countries.