Anaerobic digestion of agricultural wastes and comparison between conventional and automated biochemical methane potential performance

Abstract

Biogas potential assessment of organic waste is an interesting practice exploited to enhance sustainable energy recovery while mitigating the environmental burdens associated with waste disposal. However, there are still some incongruences regarding the method's accuracy. The biogas potential of four agro-wastes, i.e., banana peel, banana pulp, cocoa, and coffee mucilages, via the conventional and automated method, was established, and the characteristics between them were determined. The highest biogas yield was observed with the automated and the conventional methods under continuous mixing, which were roughly 27% higher than those obtained with the conventional method under intermittent mixing. Among the substrates, the most significant biogas production was recorded for coffee (1067 mL·g_TVS⁻¹), followed by cocoa mucilage (748 mL·g_TVS⁻¹). The biogas collection values from the automated method were similar to those from the stirred method, but the automated method showed earlier stabilized methane formation. For cocoa mucilage, the time to reach 80% of the maximum biogas (T₈₀) was the shortest, denoting its fast hydrolysis in fermentation. An apparent biodegradability index was estimated by relating the experimental biogas volume (L_{experimental biogas} per g _{digested TVS}) to the theoretical biogas potential of the substrate’s volatile solids (L_{theoretical biogas} per g _{digested TVS}), with coffee mucilage identified as the most apparently biodegradable biomass.