The landfill off N.C. 55 that swallows tons of Wake County’s household trash every day is now also the site of a small power plant.
County officials and representatives of Duke Energy and INGENCO, the company that runs the South Wake Landfill Gas-to-Energy Facility, gathered Thursday to celebrate the plant, which began operating last September. Earplugs were required, because the sound of 14 turbocharged engines producing 4 megawatts of power is deafening.
INGENCO, a company based in Richmond, Va., that specializes in gas electricity generation, developed this system to convert landfill gas into electricity, which is then sold to Duke Energy Progress. The county receives 22 percent of the revenue.
“We take the gas that would otherwise be simply destroyed for no beneficial use, and we take it over to our facility here and we generate electricity that goes up and down the road to homes and businesses directly,” said Alan Petersen, INGENCO’s vice president of development.
At least 30 landfills in North Carolina, including the closed North Wake Landfill in Raleigh, generate power from the methane produced by rotting garbage, according to the U.S. Environmental Protection Agency.
Johnston County started burning landfill gas a year ago, producing enough electricity to power 1,500 homes.
Wake chose INGENCO for the South Wake Landfill project from a pool of seven proposals to reuse the landfill gas. The request for proposals went out in 2010, two years after the South Wake facility opened in February 2008.
Initially, the methane gas generated by waste in the landfill was burned off, through a process known as flaring, to minimize its impact on the environment. Methane is a greenhouse gas that traps heat in the atmosphere.
“The problem with methane is methane is 20-plus times more harmful to the environment than carbon dioxide, so you’re better to at least burn the methane,” said John Roberson, the county’s director of solid waste management.
But the county wanted to put the gas to use, by blending landfill gas comprised of about 50 percent methane with diesel fuel and using it to power the engines that generate electricity.
The rest of the gas is 35 percent carbon dioxide and about 15 percent nitrogen, volatile organic compounds and garbage.
Optimally, the facility can produce 6 megawatts of energy through 18 engines, with plans to expand to as many as 24. Though maintaining a 50 percent methane concentration is key, the system can burn down to about 32 percent methane, said Tom Hecmanczuk, INGENCO’s director of construction.
“Every two weeks someone goes down into the wells and, based on flow of air, monitors the methane percentage,” Hecmanczuk said. “If it’s producing 45 percent, they might reduce the flow by closing the valve a little bit. If it’s 55 percent, they may open the valve a little bit more so they can get more flow.”
Using landfill gas to create electricity is a good investment that will pay off for years to come, said Phil Matthews, chairman of the Wake County Board of Commissioners.
“We do have landfills, and there’s not going to be a shortage of them in Wake County,” Matthews said. “I don’t see why we can’t take this process to all of them and have them continue to work for us long, long after they’re filled up.”