Electricity and Carbon Offsets from Hog Waste

A system constructed by Duke University and Duke Energy on a hog finishing facility converts hog waste into electricity and creates carbon offset credits. Google, which invests in carbon offsets to fulfill its own carbon neutrality goals, announced its endorsement of the project this week.

By capturing greenhouse gases from hog waste and burning them to run a turbine, the $1.2 million prototype system produces enough electricity to power 35 homes for a year. It is expected to be able to prevent the release of greenhouse gases equivalent to nearly 5,000 metric tons of CO2 per year.

Open waste lagoons currently in use on most North Carolina hog finishing farms are prolific producers of methane gas, which is 21 times more potent than carbon dioxide, pound-for-pound, as a greenhouse gas.

The system was built at Loyd Ray Farms, a 9,000-head hog finishing operation northwest of Yadkinville, NC. Though it is an established farm, the system meets North Carolina's environmental standards for new and expanded hog farms. The system includes a lined and covered anaerobic digester and a lined aeration basin. Methane gas is collected under a thick plastic dome over the digester. Gas which isn't burned in the turbine is burned in a flare to prevent its release.

Duke University and Duke Energy have been developing the pilot project for almost three years, with additional grant funding from the U.S. Department of Agriculture and the North Carolina Department of Environment and Natural Resources Lagoon Conversion Program. Duke Energy and the university will share operational and maintenance costs for the first ten years of operation. Google will assume a share of the university's portion of the costs in return for a portion of the carbon offsets for a five-year term.

The project is expected to yield many benefits beyond renewable energy production and greenhouse gas reductions - including improved water and air quality; reduced odors, pathogens, and nutrients; and increased farm productivity.

Capturing the methane creates carbon offset credits for Duke University and Google and using it to generate electricity creates renewable energy credits for Duke Energy. Loyd Ray Farms will use surplus electricity on-site.

(Duke University)