“We have to deal with this waste somehow.”
Meltem Urgun Demirtas
For companies interested in anaerobic digestion, however, methane production is the goal. Because these facilities are closed, biogas, a mixture of methane and carbon dioxide produced by microorganisms called biogas, is captured and refined into biomethane, which can be used as a substitute for natural gas.
Some producers burn this biomethane (also called renewable natural gas) or on-site raw biogas to heat their facilities. Others are sold to utilities, so it’s piped into existing natural gas pipelines and used to generate electricity in power plants or used for heating or cooking in homes.
Anaerobic digestion generally benefits the climate, but how much the process reduces emissions depends heavily on the details, says Troy Hawkins of Argonne National Laboratory, who studies the environmental impact of energy systems.
Divert works with more than 5,000 retail stores across the U.S. to collect food waste and process it using anaerobic digestion. The company currently operates 10 food processing stations in the U.S. and uses tracking systems to understand why some food goes to waste in the first place, Begin added.
Deploying anaerobic digesters is not cheap: a full-scale facility can cost tens or hundreds of millions of dollars. Designing new utilities can be time-consuming, as most are tailored for specific processing tasks. An on-site facility for an ice cream factory may look different than one that can accept everything from grocery waste like expired frozen pizzas and old apples to restaurants’ cooking oils, McKiernan says.
More than 11,000 additional sites in the US are ripe for the deployment of anaerobic digesters, from wastewater facilities to food waste sites, according to a 2014 report by US federal agencies. If all these facilities were built, they could generate enough energy to power 3 million homes. The American Biogas Council, an industry trade group, puts the number at 15,000 sites, which would require about $45 billion to build in total.
It won’t be cheap and it won’t be fast, but anaerobic digesters could be a significant destination for food waste in the future, helping to turn one person’s table into another person’s energy.
Correction: An earlier version of this article misstated a quote from Sean Kreloff.