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Anaerobic Digestion's Role in Dealing with America's Food Waste

Last month, the U.S. Department of Agriculture (USDA) and Environmental Protection Agency (EPA) jointly announced the nation’s first food waste reduction goal: a 50 percent reduction in food waste sent to landfills by 2030. “By reducing wasted food in landfills, we cut harmful methane emissions that fuel climate change, conserve our natural resources, and protect our planet for future generations” EPA Administrator Gina McCarthy said of the new goal. Based on EPA’s 2013 numbers, nearly 18 million tons food waste must be diverted each year to meet the target. This is certainly no small task, and questions remain as to how the goal will be achieved.

Much of the initial discussion has focused on the donation of post-consumer food waste to combat food insecurity across the country. Post-consumer streams include discards from homes, restaurants, schools, and grocery stores. According to recent studies by the Food Waste Reduction Alliance and the U.K.-based WRAP, nearly half of post-consumer food waste comes from households and less substantial portions are sourced from restaurant, school and grocery store food wastes.

However, it is estimated that most of these food wastes are spoiled or otherwise unfit for donation, which suggests that donating post-consumer food waste could play a relatively minor role in achieving this goal unless different strategies are developed to deter spoilage. Inedible food waste will almost certainly end up curbside, even with a drastic increase in food donation. Once curbside, what can be done with this portion to help meet the goal? A number of waste management options exist to divert this material, as well as pre-consumer food waste, from landfills.

The most common waste management alternative for food waste is composting. Recent work by the Institute for Local Self-Reliance identified 374 composting facilities in the United States that include food waste as part of their feedstock. Roughly 5 percent of food waste was recovered through these facilities in 2013, based on EPA estimates.

In addition to composting, other management alternatives exist to process this material. One technology that has received increasing interest in recent years is anaerobic digestion (AD), which has the ability to manage organic wastes including: post-consumer food waste, food processing solids and liquids, and fats oils and grease (FOG). Food waste can serve as the main feedstock at stand-alone AD facilities, or added to farm or wastewater organics at co-digestion facilities.

In August, the Environmental Research and Education Foundation published a study on the management of MSW through AD. The Foundation identified 153 AD facilities accepting pre- or post-consumer food waste and estimates an additional 2 percent of the nation’s food waste was diverted from landfills to these facilities in 2013. Diversion to AD is expected to increase in the coming years, as many facilities are currently in planning, permitting, or construction phases. If all AD projects planned through 2017 come online, stand-alone facility capacity will increase by over 4.5 times. This could provide a potential endpoint for one-fifth of the food waste that must be diverted to meet the new landfill reduction goal.

The USDA and EPA’s goal seeks to engage private sector, charitable and faith-based organizations to increase food donation for the 48.1 million people affected by food insecurity in the United States. Given that not all food waste is suitable for consumption, this suggests that the solid waste industry will play an integral role; and a combination of management options such as composting, anaerobic digestion, and others could be used to provide the required capacity.

Debra Kantner is the Internal Research Program Manager at the Environmental Research and Education Foundation (EREF), and co-author of the recent EREF report “Anaerobic Digestion of Municipal Solid Waste: Report on the State of Practice.” More information on the study, including access to the final report, can be obtained at the Foundation’s website

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