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.

Keywords:

• anaerobic co-digestion
• fat
• oil
• and grease
• biogas production
• mesophilic
• thermophilic
• semi-continuous digester

Acknowledgements

The authors acknowledge the Natural Sciences and Engineering Research Council of Canada Strategic Project Grant and Discovery Grant programmes, the Ontario Ministry of Research Innovation and Early Researcher Award programme that funded this work, as well as Ravensview Water Pollution Control Plant, Utilities Kingston (Kingston, Canada) for site assistance, including reactor operation and sludge collection throughout the project.