A Duke Energy power plant is using renewable natural gas from North Carolina-based hog farms to produce electricity.

Also called directed biogas, the Optima KV project captures methane gas from the hog waste of five farms. Using more than 42,000 feet of in-ground piping, the methane is moved to a central location where the gas is cleaned and converted to pipeline-quality natural gas.

The project injects the renewable natural gas into the Piedmont Natural Gas system, which transports it to Duke Energy's Smith Energy Complex where it is used to produce electricity.

The Duplin County location for the facility is in the heart of Smithfield Foods' pork operations.

The project stems from North Carolina's Renewable Energy Portfolio Standard, which required the utility to meet specific compliance targets for swine and poultry waste.

Under a 15-year contract, Optima KV is expected to produce about 80,000 mmbtus of pipeline-quality captured methane a year. Duke Energy should yield about 11,000 megawatt-hours of renewable energy annually, enough to power about 880 homes for a year. The renewable energy credits generated by the effort will help meet state mandates.