EXETER, Maine — Exeter Agri-Energy deemed its first full year of operation a success.
The anaerobic digestion facility at Stonyvale Farm celebrated its first anniversary last month. The facility co-digests manure and food waste on a large scale to create heat and electricity.
“We combined about 7.3 million gallons of cow manure with food waste in our first year, allowing us to produce 5.2 million kilowatt-hours of electricity for the grid,” said Adam Wintle, managing partner for Biogas Energy Partners, the developing arm of Exeter Agri-Energy. “That’s good in itself, but our secret recipe, so to speak, is what has the industry taking notice.”
The farm sells all of its electricity to Bangor Hydro-Electric Co. Whatever electricity the farm needs it buys back from Bangor Hydro.
“If we were to use the energy here on site, we would probably consume about 5 percent of that on an annual basis,” Wintle said last June. “So that gives you a relative scale of production of Stonyvale Farms.”
The facility, which began operating Dec. 29, 2012, is the only one of its kind in New England that co-digests manure and food waste on a large scale, said Wintle.
In addition to producing electricity, Exeter Agri-Energy said the facility benefits the ecosystem through helping clean watersheds near the dairy farm, landfill conservation, reduced methane pollution and economic development.
The dairy farm, which has 1,800 livestock, produces a lot of waste. The waste is piped to two big digestion vessels where it is mixed with food waste. The biogas given off by the mixture fuels a 16-cylinder, 1,500-horsepower engine. The engine produces about 4 million Btu of heat per hour — enough to replace 700 gallons of heating oil per day.