Bench- and Full-Scale Anaerobic Co-Digestion of Fats Oil and Grease, Food Waste, and Vegetable Cooking Oil for Enhanced Biogas Production

Anaerobic co-digestion can improve energy recovery during wastewater treatment by enhancing biogas production from primary sludge (PS), thickened waste activated sludge (TWAS), and other substrates. In this study, an initial full-scale investigation of the anaerobic co-digestion of PS, TWAS, vegetable cooking oil (VCO), and food waste was conducted at the Hyperion Wastewater Treatment Plant (wwtp; Los Angeles, CA) to evaluate improvements in digester performance. In a parallel study, co-digestion of PS, TWAS, fats oils and grease (FOG), and food waste were evaluated using bench-scale anaerobic respirometry. At the full-scale, co-digestion of PS, TWAS, and either VCO or food waste negligibly improved reactor performance. However, co-digestion of all substrates increased biogas production by 15% when VCO and food waste were added at only 2 and 5% volatile solid loading (VSL), respectively. Ongoing bench-scale respirometry experiments suggest that FOG addition results in a lag time in biogas production. We expect these experiments to inform decisions at the full-scale regarding substrate mixtures and maximum organic loading rates.