Food Waste or Fuel Source?

Hahvee…take out the gahbidge…it stinks!” my mom used to remind me of my household chore growing up in Pawtucket, R.I., in the ’60s. We had a 30-gallon can for food waste in the back corner of our lot waiting to be collected by the city and delivered to pig farmers for feed. Neighboring Providence did it a little differently: It had to be bundled in newspapers and set out for collection, eventually to find its way to pig farmers.

Fast-forward to the new millennium. We are serious about increasing recycling even more by going after organics. The U.S. Environmental Protection Agency reports that food waste accounts for approximately 21 percent of landfilled municipal solid waste (MSW), or around 35 million tons per year (TPY). This waste is a resource that can be used to produce biogas, for power production or vehicle fuels, and compost. Communities and companies throughout the U.S. have recognized its value and include food waste diversion as a part of their sustainability plans.

States have started to support food waste diversion through regulatory initiatives and financial incentives. Landfill bans on food waste from commercial generators (grocery stores, cafeterias, restaurants and food manufacturing) are in place in Connecticut, Massachusetts and Vermont. California, Washington, Oregon and other locations have set up MSW landfill diversion goals as high as 75 percent that can be reached only by including food waste. Federal and state financial incentives are available to support communities and private entities looking to use food waste to produce renewable energy. When Massachusetts banned commercial food waste in 2013, its Department of Energy Resources offered $3 million in low-interest loans for private companies building anaerobic digestion (AD) facilities.

However, getting food waste from generators to processing facilities can be a challenge. Residential food waste can be collected separately or commingled with yard waste. Separate collection of food waste is more expensive, so an increasing number of communities are instituting food waste collection programs that combine food and yard waste.

Local wastewater treatment infrastructure also can play an important role in residential food waste reclamation. Food waste has three times the methane potential of biosolids, and its potential for renewable energy generation can be captured by wastewater treatment facilities with AD components. With some 1,200 wastewater treatment plant digesters around the U.S., according to BioCNG, a producer of biogas-based fuel for vehicles, areas with excess digester capacity can encourage households with garbage disposals to use them more and see an uptick in organics flow to their existing or expanded AD systems.

Commercial food waste collection is less challenging. At least one major supermarket chain, Kroger, has decided to manage some food waste in-house. Kroger opened a 55,000-TPY AD facility for food waste at its distribution center in Compton, Calif. The biogas produced is used to power on-site production operations. (For more on this system, see “Good Faith Efforts,” beginning on page 33.)

Meanwhile, much of the food waste collected around the U.S. is processed at 500 (out of around 2,300) composting plants (Source: Biocycle). Significant composting infrastructure can be changed to take cocollected residential yard waste and food waste. However, the product here is compost, not energy.

Food waste that reaches AD can produce renewable energy or fuel. For example, a stream of 50 to 75 tons per day of food waste has the potential to produce 200 cubic feet per minute (cfm) of biogas with 60 percent methane content. BioCNG estimates this 200 cfm of biogas has the fuel production potential of 320,000 diesel gallon equivalents (DGEs) per year, enough fuel for 50 to 60 light-duty vehicles, with annual fuel savings of $640,000 over diesel, based on current fuel pricing. If we extrapolated this to 50 percent of the food waste disposed now, that would be enough for about 40,000 vehicles!

Perhaps as food-waste-to-fuel systems become more common, people will think differently about throwing out their leftovers— instead of feeding pigs, we could be fueling cars!

GBB Consultant II Elizabeth Rice provided research support.

Harvey Gershman, hgershman@gbbinc.com, is president of Gershman, Brickner & Bratton Inc., solid waste management consultants.