Operational Parameters Affecting Methane Yield and Volatile Solids Removal in Food Waste Anaerobic Digestion: A Review

Abstract

Food waste is a biodegradable resource with potential for energy recovery through anaerobic digestion. However, digestion performance varies with substrate characteristics, reactor configurations, and operating conditions. This review evaluates the effects of feed-to-inoculum ratio, organic loading rate, hydraulic retention time, temperature, pH, and mixing, and compares mono-digestion and co-digestion systems using methane yield and volatile solids (VS) removal. Among studies reporting methane yield on a VS basis, values ranged from 0.260 to 0.392 m³ CH 4 kg –1 VS, while reported VS reduction ranged from 60 to 82%. Excessive substrate loading may increase treatment capacity but reduce methane yield through volatile fatty acid accumulation, whereas sufficient inoculum and retention time support stable conversion. Co-digestion is most effective when co-substrates improve the C/N ratio and buffering capacity, although slowly biodegradable solids may reduce methane recovery. These findings demonstrate that effective optimisation requires balancing methane yield, organic matter removal, process stability, and reactor capacity.