OPTIMIZATION OF BIOGAS PRODUCTION FROMTHEBLENDOFCASSAVA, YAM, AND POTATO PEELS

This study aim to optimize biogas production from the co-digestion of cassava, yam, and potato peels with cow dung as inoculum, addressing the dual challenges of agricultural waste management and renewable energy generation in Nigeria. The research sought to determine the most effective substrate mixing ratios and associated process conditions that enhance biogas yield and methane content while providing sustainable solutions for converting abundant agricultural residues into clean energy. The optimization was conducted through batch anaerobic digestion at laboratory scale using asimplex lattice mixture design approach. The study involved three consecutive batches with four experimental runs each, totaling twelve runs over an 8-day hydraulic retention time per batch. Fresh cattle rumen was obtained from Abattoir Oluku, while cassava peels were sourced from the Ogba community, and yam and potato peels were collected from Ekosodin, Ugbowo community, all in Edo State, Nigeria. The feedstocks underwent systematic pre treatment including washing, oven drying at 100 - 130°C for 18 hours, grinding usingmortar and pestle followed by manual hand grinding, and sieving through 500-micromeshtoachieve uniform particle size. Proximate analysis determine moisture content, ash content, volatile matter, and fixed carbon, while ultimate analysis using Energy – Dispersive X-ray Fluorescence (EDXRF) spectrometry establish elemental composition including carbon-nitrogen ratios. A fixed mass of 50g cow dung dissolved in 150ml water served as inoculum for each experimental run. The biogas volume was measured using the water displacement method with Buchner flask setups, and statistical analysis was performed using Response Surface Methodology and Analysis of Variance (ANOVA) through Design Expert software to evaluate model significance and develop predictive equations. The results revealed that pure yam peel produced the highest biogas yield of 180ml/50g.week with excellent methane concentration of 88.2%, significantly outperforming cassava peel (98.4 ml/50g.week, 86.7% CH₄) and potato peel (70 ml/50g.week, 82.5%CH₄). The binary blend of yam and cassava peels demonstrated synergistic effects with147.5ml/50g.week yield and 87.9% methane content, while yam-potato combinations exhibitedstrong antagonistic interactions producing only 25 ml/50g.week. Statistical validation confirmed excellent model fit with R² values of 0.9982 for biogas yield (Special Quartic model) and 0.9523 for methane concentration (Quadratic model), both significant at p<0.001. The cow dung characterization revealed substantial nutrient content including calcium(36.20%), potassium (14.65%), phosphorus (9.62%), and nitrogen (3.89%), confirming its suitability as an effective inoculum. These findings demonstrate that strategic substrate blending, particularly yam-cassava combinations, can optimize biogas production from agricultural waste while providing practical guidelines for small-scale biogas system sin resource-limited settings.