Synergistic Co-Digestion of Napier Grass, Banana Peel, and Cow Dung for Enhanced Biogas Yield

This study investigates an anaerobic co-digestion strategy combining Napier grass (Pennisetum purpureum), banana peel, and cow dung to enhance biogas production. Napier grass is highly lignocellulosic (high carbon-to-nitrogen ratio) and requires additional nitrogen to optimize digestion; cow manure provides nitrogen and inoculum, while banana peels contribute readily degradable carbohydrates and moisture. Three feedstock blends were tested, with Napier:banana ratios of 1:1, 2:1, and 1:2 (by weight), each including cow dung. These mixtures were loaded into 5-L batch digesters and incubated under mesophilic conditions (28–35 °C) for ~23–24 days. During each run, biogas volume was measured daily (via water displacement) and slurry pH was maintained near neutral (≈6.8–7.5) to support methanogenesis. The co-digestion approach achieved a highest cumulative gas yield of ~2.48 L (2,481 mL) from the 1:1 Napier:banana blend, significantly outperforming other ratios. Gas composition analysis revealed relatively low hydrogen sulfide (~6–7 ppm) and a methane content of ~20–23%, indicating that the equimass feedstock combination exploited complementary biodegradation pathways while minimizing H₂S. These results highlight the novelty of the approach. By valorizing abundantly available agricultural residues, this co-digestion scheme not only delivers renewable fuel with reduced contaminants, but also advances sustainable energy generation for rural communities and improved waste management.