Various organizations are pursuing and implementing uses for grease waste materials. This is driven largely by rising prices for fuels and electric power, but also from the need to minimize the problems of sewer blockages, sewer overflows, and odor problems caused by such grease when discharged to local sewers. Using grease-source fuels to replace conventional fuels can also reduce greenhouse gas emissions and reduce conventional air pollutant emissions. Information collected by the authors on several recent projects is used in this paper to review the innovations, successes and problems that are occurring. Urban waste grease resources are primarily of two types (yellow grease and brown grease), and this paper discusses both in terms of energy value and energy products.

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DC WASA provides water distribution and wastewater collection and treatment services to the greater Washington, DC metropolitan area serving a population of approximately 2.1 million people. Wastewater is treated at the 370-million-gallon-per-day (mgd) Blue Plains Advanced Wastewater Treatment Plant (AWTP). DC WASA will soon replace the aging lime stabilization sludge-treatment process at the AWTP with Class-A anaerobic digestion using Cambi™ thermal hydrolysis. This upgrade will produce electricity and process heat from a renewable fuel (digester gas) while reducing the mass of produced biosolids by 50 to 60 percent. This paper will document DC WASA's GHG inventories for 2007 and 2008 and show how the proposed digestion upgrades will reduce the utility's overall inventory by an estimated 28 to 39 percent or 46,816 to 73,340 MT of CO 2 e per year.

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