EXPERIMENTAL INVESTIGATION OF BIOGAS QUALITY AND ENERGY POTENTIAL FROM SYNERGISTIC CO-DIGESTION OF CASSAVA PEELS AND COW DUNG
Abstract
The conversion of agricultural residues into renewable energy offers an environmentally sustainable solution to waste management and energy security. Cassava peels and cow dung are abundant biodegradable resources with considerable potential for anaerobic digestion; however, information on the influence of substrate blending on biogas quality and energy performance remains limited. This study investigated the effect of cassava peel–cow dung blending ratios on biogas composition, calorific value, and engineering performance to identify the optimum substrate combination for renewable energy generation. Biogas was produced using a 0.218 m³ laboratory-scale floating-drum anaerobic digester operated under batch mesophilic conditions. Five substrate blending ratios (100:0, 70:30, 50:50, 30:70, and 0:100, w/w) were evaluated. Methane (CH₄), carbon dioxide (CO₂), and hydrogen sulphide (H₂S) concentrations were measured in triplicate. The lower heating value (LHV) was estimated from methane concentration, while generator calibration was used to determine biogas consumption rate, substrate requirement, digester size, and carbon dioxide emission reduction. The 50:50 cassava peel–cow dung blend produced the highest methane concentration (63.4%), the lowest carbon dioxide concentration (35.0%), and the highest lower heating value (22.7 MJ m⁻³). The calibrated biogas consumption rate was 0.37 m³ h⁻¹, producing an average electrical output of approximately 1.5 kW. Continuous 24-hour operation required 8.88 m³ day⁻¹ of biogas, 33.84 kg day⁻¹ of substrate, and a 100.8 m³ digester. Replacing petrol with biogas reduced carbon dioxide emissions by up to 38.81 kg day⁻¹. Co-digestion of cassava peels and cow dung significantly improved biogas quality and energy potential. The 50:50 blending ratio produced the highest-quality biogas and demonstrated the feasibility of utilising agricultural residues as a sustainable feedstock for decentralised renewable energy generation.