Converting Food Waste to Renewable Energy: Greg Williams

The U.S. Department of Agriculture (USDA) estimated in 2010 that between 30-40 percent of the food supply is wasted each year. To put a dent in food waste that enters landfills regionally, Agri-Cycle, a Maine-based food waste collection service, has been turning it into a valuable resource since 2012, creating clean energy and healthy soil through an anaerobic digestion processor. Since then, the business has expanded to include partner sites and collection routes from rural northern Maine, throughout New England, and the Mid-Atlantic, including food waste from local transfer stations, grocery stores, restaurants, and colleges, powering roughly 3,000 homes annually and growing.

Located on a fifth-generation dairy farm near Exeter, Agri-Cycle works with partners like Exeter Agri-Energy, which processes the food waste effectively using a large-scale system of three anaerobic digesters to mix the collected food waste with manure from the nearby dairy barn. They can then extract the methane gas for energy with a 24/7 continuous feed system. A large press squeezes out the liquid from the mixed waste, which is spread on the fields while the solid byproduct is used as bedding for the dairy cows next door.

“Once the farm has the opportunity to use whatever energy it needs on a daily basis for electricity, the rest, which is a substantial amount, goes into the grid,” said Greg Williams, Director of Organics at Agri-Cycle. “The farm doesn’t use that much compared to what’s being generated.”

The Exeter site can generate 70,000 kWh of electricity daily, enough to power as many as 2,500 households annually.

“The reason why we’re doing all this is food waste. If it were just 124 thrown in the municipal solid waste stream with typical garbage, it would primarily end up in a landfill, with some exceptions like ecomaine. And when you bury food waste, it generates methane that’s released into the atmosphere without any control,” said Williams.

Even food scraps redirected from ecomaine, a sustainable food waste management nonprofit, have an impact.

“Even though it’s not going to a landfill and creating methane [at ecomaine], it’s still very wet, so it’s like putting soup on your campfire. It’s really hard to burn through because it’s just so wet.”

Agri-Cycle also has a system to extract food waste that’s not fit for human consumption and still in packaging, like cans, bags and plastic containers. That makes it easier and cheaper for large-scale food sites to dispose of their food waste for an efficient use.

Williams sees the diversion of food waste as an opportunity for climate action for individuals and systems alike. “Not everyone can afford an electric car necessarily, but maybe food waste diversion is one of those things that everybody can do,” he said. “Anybody can divert their food if they have the space, so it’s taken hold pretty quickly, and it’s an empowering opportunity to make real change in small doses and collectively.”

“It makes no sense when we can do something much more practical with it by capturing methane in a controlled way and making renewable electricity from it.”