A Full-Scale Demonstration Food Waste and Sewage Sludge Co-Digestion Project at the Joint Water Pollution Control Plant

The Los Angeles County Sanitation Districts (Districts) and Waste Management (WM) are conducting a multi-year demonstration project to study the collection, processing, delivery and anaerobic digestion of processed food waste. This study is being conducted at the Districts’ Joint Water Pollution Control Plant to help determine if handling food waste in anaerobic digesters can be a commercially viable alternative to using landfills. Co-digestion of food waste with primary and thickened waste activated sludges in one of the Districts’ anaerobic digesters has been performed for over a 16 month period. After an initial ramp-up period to acclimate a test digester, approximately 30 tons/day of processed food waste was fed for over an eight month period. The test digester operation was compared to control digesters for operational parameters such as volatile acids, alkalinity and volatile solids destruction. Although the amount of food waste was added to the test digester at about 3% of the total volumetric feedstock flow, it increased digester gas production by 25 to 30 percent.