Effects of slurry concentration and co-digestion on biogas yields from unseeded Phaseolus vulgaris (bean) peels chaff and unseeded Musa paradisiaca (plantain) peels chaff

This study explored converting agricultural wastes of Bean peel chaff (Bu) and Plantain peel chaff (Pu) into biogas, an eco-friendly biofuel, without cow rumen liquor. By digesting these wastes anaerobically in various combinations and slurry concentrations, the study assessed their individual and combined biogas yields. Bean and plantain peels were digested alone and in two mixtures: BP1u (bean-to-plantain ratio 0.691:1) and BP2u (1:1 ratio). Three waste-to-water slurry concentrations (1:6, 1:11, and 1:16) were used, with anaerobic digestion lasting 37 days in triplicate 1000ml mini digesters. Biogas production was measured via water displacement. The study found total solids percentages of 96.03% for Bu, 90.12% for Pu, 84.15% for BP1u, and 84.94% for BP2u. The carbon/nitrogen (C/N) ratios ranged from 9.04 to 15.3. Average biogas yields showed BP1u produced the highest (11.12 ml/day), followed by Bu (9.8 ml/day), BP2u (7.5 ml/day), and Pu (0.55 ml/day). Among slurry concentrations, 1:6 (C1) yielded the most biogas (17.45 ml/day), followed by 1:11 (C2) and 1:16 (C3). ANOVA indicated significant effects from both slurry concentration and co-digestion on biogas yield, along with a notable interaction between both factors. In conclusion, both bean and plantain peels can generate biogas effectively, especially when combined and digested in higher slurry concentrations for improved yield. This approach supports waste management and renewable energy goals by transforming agricultural residues into valuable biofuel.