4Waste Grease Biodiesel Production at a Wastewater Treatment Plant

East Bay Municipal Utility District (EBMUD) conducted a pilot study to demonstrate the production and use of biodiesel from interceptor grease waste. Bench-scale testing was followed by pilot-scale production of 200 to 400-L batches. Brown grease with a free fatty acid (FFA) content of 54-100% was obtained from interceptor grease hauled to EBMUD's wastewater treatment plant. Free fatty acids were converted using a one or two step acid esterification reaction and triglycerides were converted using a sodium methoxide catalyzed transesterification reaction, both at ambient temperatures. Impurities associated with the brown grease, such as sulfur, proved to be problematic. Biodiesel was used to fuel heavy duty diesel trucks as B20 and B100 for multiple weeks. No operational or performance problems were reported. Preliminary energy and economic comparison to anaerobic digestion show a more favorable energy balance for biodiesel and a potentially more favorable economic value for biodiesel, but with significant risk.