EXETER — A family dairy farm in central Maine is using a new system that converts cow manure and food waste into heat and electricity.

Maine’s top environmental, agriculture and economic development officials will be on hand today when the anaerobic digestion system is unveiled at the Stonyvale Farm in Exeter, which has about 1,000 cows.

Stonyvale Farm is selling the electricity to the region’s power grid. It has formed a new company, called Exeter Agri-Energy, to run the operation.

The excess heat from the system is being used to heat the farm’s own buildings.

The farm began producing electricity several months ago and produces enough to supply the power needs of 800 homes.