Enhanced biogas production from food waste via enzymatic hydrolysis and fermentation : a comprehensive study

Abstract

Food waste requires sustainable management to reduce environmental impacts and enhance economic value, with anaerobic fermentation being a reliable solution. Enzymatic hydrolysis can further improve these processes, boosting biofuel production efficiency. This study investigates the potential of mixed food waste (MFW), spent coffee grounds (SCG), and fruit waste (FrW) to maximize biomethane and biohydrogen output by identifying effective enzymes for hydrolysis, with a focus on sugar recovery from SCG. Biomethane potential tests were conducted for MFW and SCG, while biogas tests were performed for FrW. Biogas composition was analysed using a biogas analyser, and the effects of pH and time on methane yield were studied using Response Surface Methodology (RSM). Substrates and digestates were characterized using proximate analysis, monosaccharide analysis with GC, and thermal and chemical profiling with TGA and FTIR. The BE enzyme achieved the highest sugar yield (6930 mg/L) in SCG, while the XC enzyme achieved a record methane yield of 400 mL CH₄/gVS with a 39% energy yield, significantly reducing the lag phase and optimizing methane production at a pH range of 4.19–4.39 in SCG within 12–48 hours. FrW showed strong biohydrogen potential (54%). Future research should focus on scaling up these findings, evaluating the economic and energy feasibility of using XC and BE enzymes in large-scale biomethane and biohydrogen production, and exploring the potential of digestates for Hydrothermal Carbonization (HTC) to produce hydrochar for soil or energy use.