“We need to manage this waste somehow.”
Meltem Urgun Demirtas
However, for companies interested in anaerobic digestion, the goal is methane production. Because these facilities are closed, the mixture of methane and carbon dioxide produced by microbes, called biogas, can be captured and purified into biomethane, which can be used as a substitute for natural gas.
Some producers use this biomethane (also called renewable natural gas) or raw biogas on-site, burning it to power their facilities. Others sell it to utilities, so it is fed into existing gas pipelines and used to generate electricity in power plants or used in homes for heating or cooking.
Overall, anaerobic digestion can benefit the climate, but exactly how much the process will reduce emissions will depend on the details, says Troy Hawkins, a research scientist at Argonne National Laboratory who studies the environmental impact of energy systems.
Divert works with more than 5,000 retail stores in the U.S. to collect food waste and process it through anaerobic digestion. The company currently operates 10 digesters in the U.S. and uses tracking systems to understand why certain food goes to waste in the first place, Begin adds.
Anaerobics are not cheap to deploy: a full-scale installation can cost tens or hundreds of millions of dollars. Designing new facilities can also take time because most are customized for specific processing tasks. According to McKiernan, the space for an ice cream factory can look different than a facility that can accept everything from grocery store waste, such as expired frozen pizzas and old apples, to used cooking oil from restaurants.
According to a 2014 report by US federal agencies, more than 11,000 additional facilities in the US are ripe for the deployment of anaerobic varieties, from sewage treatment plants to food waste landfills. 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 figure at 15,000 facilities, which would cost about $45 billion to build.
It won’t be cheap or fast, but in the future, anaerobic digesters could become a significant destination for food waste, helping to turn one person’s table scraps into another’s energy.