SC prison converts cow dung into natural gas • SC Daily Gazette

COLUMBIA — An inmate-run gas plant at a South Carolina prison will convert cow manure into renewable energy that can power major businesses in the state.

Charleston-based GreenGas USA plans to spend $14.5 million to build a natural gas plant on property at the Wateree River Correctional Institution in rural Sumter County.

The plant would convert cow manure from the prison's dairy farm and food scraps from the prison's kitchens into a renewable energy source, according to a proposal presented to lawmakers when they approved the project last month.

“It's a win-win situation,” said Senator Katrina Shealy (R-Lexington) at a meeting last month. “We get rid of the cow manure, generate energy and do something useful in the prison.”

Half of GreenGas' profits from the gas produced at the Wateree River plant would go to the Department of Corrections, and the company would pay the state $100,000 annually for 20 years to lease the land, the proposal says.

The state will not invest any money in the program.

“It means money for the state,” said Bryan Stirling, director of the Department of Corrections. “It means that the waste that comes from cow manure and ultimately chicken and food is sold and becomes renewable energy for big companies like BMW and Mercedes.”

The program will teach 20 inmates skills that could land them jobs paying more than $60,000 upon their release, Stirling told lawmakers.

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The tasks will mainly involve maintenance work, such as electrical wiring and repairing pumps and valves to ensure the plant runs smoothly, Marc Fetten, CEO of GreenGas, told the Daily Gazette, adding that he is not aware of any other prison in the country that has a similar program.

GreenGas will source the fertilizer from the prison's existing 1,200-cow dairy farm. Inmates already handle farm work by caring for the cows, Fetten said.

“I think it's a great way to go from a not-so-great situation that (inmates) ended up in to becoming productive members of society,” Fetten said.

GreenGas plans to build its 80,000-square-foot gas-fired power plant on 4.5 acres of the Wateree River Correctional's 6,000-acre farm, and it is expected to begin producing energy in early 2026, Fetten said.

The company will start with two sealed tanks in which microorganisms will decompose cow manure and food scraps from the prison system's kitchens. As the food and manure decompose, they will release methane and carbon dioxide, which will be trapped in the tanks.

The decomposition process takes place independently, but GreenGas cleans the gases and sells them to companies.

“Think of a traditional compost pile that some of us may have had in our backyard as children,” Fetten said.

After decompression, the gas will be transported to customers via existing pipelines. GreenGas has customers willing to buy, but Fetten declined to name them, citing confidentiality agreements.

These companies could benefit from a cleaner energy source that, unlike wind or solar power, does not require them to convert their entire electricity system, Fetten said.

Sources of waste large enough to make a difference, such as the state prison system and its large dairy farm, are hard to find, he said.

The methane produced at the prison facility will be enough to power factories. About a third of the byproduct will be carbon dioxide, which GreenGas can sell separately to customers for cooling and carbonation.

GreenGas also operates plants that convert waste into gas at McCall Farms in Effingham and Amick Farms in Batesburg. But those private farms can't meet the demand for natural gas, Fetten says.

“From an economic development perspective, these companies are crying out for renewable energy and we have frankly been desperate for sources,” Fetten told lawmakers.