Optimisation of Biogas Production from Plantain (Musa paradisiaca) Lignocellulosic Residues using Anaerobic Digestion

Abstract

The increasing generation of plantain (Musa paradisiaca) residues presents both a waste-management challenge and an opportunity for renewable-energy recovery. This study investigated the anaerobic digestion of plantain residues for biogas production and optimised the process using response surface methodology. Plantain peel and mixed plantain residues were characterised for physicochemical and microbiological properties before digestion. The effects of substrate concentration, inoculum concentration, pH and digestion time on biogas production were evaluated using a response surface experimental design. Biogas volume, methane concentration, volatile-solids reduction and other process parameters were determined during digestion. The results showed that the plantain residues contained substantial biodegradable organic matter, with volatile solids of 88.64–90.21% of total solids and carbon-to-nitrogen ratios of 37.00–39.41. The highest cumulative biogas production was obtained from the mixed plantain residue supplemented with cow-dung inoculum. The corresponding biogas yield was 0.61 L/g volatile solids, with a methane concentration of 62.30% and volatile-solids reduction of 74.52%. COD, BOD₅, total solids and organic carbon were reduced by 76.78%, 79.57%, 65.06% and 58.11%, respectively. The response surface model was statistically significant (p < 0.001), with an R² of 0.9970 and a non-significant lack of fit (p = 0.975). The predicted optimum conditions were a substrate concentration of 9.2%, inoculum concentration of 18.4%, pH of 6.72 and digestion time of 24.6 days, giving a predicted biogas yield of 0.63 L/g volatile solids. Experimental validation produced 0.61 L/g volatile solids, representing a prediction error of 3.17%. The findings demonstrate the potential of plantain residues as substrates for renewable biogas production and provide optimised conditions for improving digestion efficiency.