From Grease to Green: Two Case Studies of FOG Receiving, Co-Digestion and Combined Heat and Power Generation

Increasingly, wastewater treatment utilities are considering the dual benefits associated with fats, oils, and grease (FOG) receiving. Receiving this material can help to address the removal of a problematic material from the collection system by facilitating periodic grease trap cleaning and maintenance at food service establishments (FSEs) in their service areas. Through co-digestion of this material with traditional wastewater solids in anaerobic digesters, the utility can simultaneously realize benefits from increased digester gas production. Two case studies are presented, the F. Wayne Hill Water Resources Center (FWHWRC) in Gwinnett County, Georgia and the Henrico County (Virginia) Water Reclamation Facility (HCWRF), to demonstrate the unique driving factors, design concerns and economic benefits from receiving FOG for co-digestion. The various drivers for the projects include both internal (collection and treatment system impacts from FOG, economics) and external (changing regulations, available grant funding opportunities) to the wastewater utility. Design concerns span the FOG receiving facilities, the use of existing anaerobic digesters for co-digestion and operation of the CHP system. Economic benefits include direct benefits from the electricity and heat produced by the CHP system and indirect benefits from the removal of the FOG from the collection and treatment systems.