Producing green energy from post-consumer solid food wastes at a wastewater treatment plant using an innovative new process

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ABSTRACT

More than 246 million tons of municipal solid waste (MSW) was generated in the United States in 2005, and this tonnage is expected to increase every year. The third highest component of MSW is food waste, but less than 3% of food waste is recycled. In an effort to meet the U.S. Environmental Protection Agency’s national 35% MSW recycling goal, and many states’ and local governments’ more stringent recycling goals, food waste recycling could become increasingly more important. Anaerobic digesters at wastewater treatment plants could be a good fit for recycling food wastes and creating green energy at the same time. Food waste, however, is a solid waste (25-35% total solids) with many contaminants that can impede or harm wastewater treatment plant processes. East Bay Municipal Utility District in Oakland, CA, developed a (patent pending) food waste recycling process that creates a food waste pulp from pre-sorted food wastes that is easily digested in wastewater treatment plant anaerobic digesters. The process has received 20-ton food waste loads, and has been successfully tested at processing rates of 20 tons/h. Bench-scale testing has shown that the food waste pulp is highly biodegradable in anaerobic digesters, with good methane gas production achieved at less than half the digester volume needed and less than half the biosolids produced compared to municipal sludges.

KEYWORDS

Food waste, anaerobic digestion, EBMUD food waste recycling process, pulp, pomace, green energy

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