Enhanced Biogas Production Using Banana Peels as Substrate and Rabbit Manure as Inoculum

Fossil fuels have long been essential in powering households and communities globally; however, their limited availability and significant environmental impacts, particularly greenhouse gas emissions, underscore the urgent need for sustainable fuel alternatives. Rising demand for cleaner energy sources has intensified interest in eco-friendly options, such as biogas production from organic residue. Utilizing materials like banana peels and rabbit manure offers a promising solution, addressing both renewable energy needs and residue disposal challenges. This study explored the potential of utilizing biomass resources, namely, banana peels (BP) and rabbit manure (RM), as feedstock for biogas generation. Due to the relatively low nutrient content and high lignin content found in BP, the use of RM, which is rich in microbial consortia with lignin-degrading microorganisms, as an inoculum in anaerobic digestion was employed to increase biogas production. This study focused on optimizing the operating variables, namely, the mass of the RM (45–105 g) and the hydraulic retention time or HRT (6 to 14 days). Design Expert 13 software was used for the central composite design of the response surface methodology. The batch experiments with 500 g of BP in each run yielded biogas ranging from 8.5 to 24.5 L, with an optimal volume of 22.45 ± 1.78 L achieved under the optimized conditions of 102 g of RM and a 10.5-day HRT. The analysis of variance indicated that a quadratic model could effectively predict biogas yield based on HRT and RM (p-value = < 0.0001), and revealing a synergistic interaction between HRT and RM mass (p-value = 0.0075) that enhances biogas yield. Under optimized conditions, gas chromatography analysis indicated a high methane concentration in the biogas yield at 70.56%, along with other detected gases: N₂ (14.33%), H₂ (9.61%), and O₂ (5.50%). Overall, this study underscores the potential of banana peels and rabbit manure as promising biomass sources for biogas production, offering an eco-friendly solution for their disposal while advancing sustainable energy alternatives.