Biogas production performance of mesophilic and thermophilic anaerobic co-digestion with fat, oil, and grease in semi-continuous flow digesters: effects of temperature, hydraulic retention time, and organic loading rate

Abstract

Anaerobic co-digestions with fat, oil, and grease (FOG) were investigated in semi-continuous flow digesters under various operating conditions. The effects of hydraulic retention times (HRTs) of 12 and 24 days, organic loading rates (OLRs) between 1.19 and 8.97 g TVS/Ld, and digestion temperatures of 37°C and 55°C on biogas production were evaluated. It was proposed that, compared to anaerobic digestion with wastewater treatment plant sludge (primary raw sludge), semi-continuous flow anaerobic co-digestion with FOG could effectively enhance biogas and methane production. Thermophilic (55°C) co-digestions exhibited higher biogas production and degradation of organics than mesophilic co-digestions. The best biogas production rate of 17.4±0.86 L/d and methane content 67.9±1.46% was obtained with a thermophilic co-digestion at HRT=24 days and OLR=2.43±0.15 g TVS/Ld. These were 32.8% and 7.10% higher than the respective values from the mesophilic co-digestion under similar operating conditions.