With methane a climate worry, landfill captures gas for energy
The 550-acre Speedway Landfill is a mountain of decomposing food, plastic and other trash in Concord. It's right off U.S. 29 next to Charlotte Motor Speedway and rises more than 100 feet above the surrounding area.
And it grows daily with deliveries by trucks from Mecklenburg, Cabarrus and surrounding counties.
"Every day we have hundreds of trucks run in here, whether it's Republic Services trucks, third-party trucks, city of Charlotte, and they run in to dispose of their waste," said Tim Ginn, who manages the landfill for its owner, Republic Services, the nation's second-largest trash hauler.
Ginn said 3,500 to 4,000 tons of trash are added every day, in an area they refer to as the "working face."
"And every night, once the trucks are out, we cover up the working face with six to eight inches of soil. And then the next day we're either working very close to that location, or jump right next to it," Ginn said.
Once all that trash is covered, it starts to decompose. That creates methane, a powerful greenhouse gas that's 28 to 36 times better than carbon dioxide at trapping heat in the atmosphere, according to the United Nations Intergovernmental Panel on Climate Change.
In the U.S. landfills are the third-largest source of human-generated methane emissions.
Before modern regulations, all that landfill methane escaped into the atmosphere. But in 1996, the EPA began requiring most landfills to install methane capture systems.
"Usually, that involves some kind of cap that has a membrane, and then a system of piping that will collect the methane and bring it to a single point. And from that point, you can basically process it," said Isaac Panzarella, associate director of the North Carolina Clean Energy Technology Center at NC State University. "Those regulations are in place because we don't want landfills to be emitting this methane just freely into the atmosphere."
The EPA estimates these systems capture between 60% and 90% of the methane in most landfills. But some experts think it's not that high.
Whatever the amount, what gets captured can be used to fuel vehicles or generate electricity, Panzarella said.
"Methane, it's a form of renewable energy. So we can basically use that to help displace fossil fuels and for generating, you know, power or thermal energy," Panzarella said.
The Speedway Landfill opened in 1992 and the first gas collection system was installed four years later. Mike Gurley, the landfill's environmental manager, said that as the landfill expands, so does the network of gas collection wells - which now numbers more than 260.
"After the garbage has been in the landfill for about six months to a year, we come in and actually continue to drill these vertical wells into the foot into the actual garbage footprint. And then at that point, we start extracting the methane as it decomposes," Gurley said.
The wells are up to 140 feet deep. Methane is sent through 18- or 24-inch pipes to the west side of the landfill. Here a contractor called Opal Fuels turns it into electricity, Ginn said as he led a tour.
"Where we're at now is we're at Opal Fuels' plant on site. It receives the methane gas that we essentially vacuum off the hill and get it to this site to be processed for energy," Ginn said.
Water, carbon dioxide and impurities are filtered out before the gas is burned in three turbines. Opal sells the electricity to Duke Energy and sends it onto the power grid. The plant's capacity of 15 megawatts can power the equivalent of 5,000 to 6,000 homes.
So that's how methane becomes a revenue source for Republic Services and a way to reduce the need for fossil fuels. The company operates 77 gas-to-energy facilities and plans to add 18 more nationwide in the next few years. A spokesperson said Republic has brought in about $50 million in revenue since it started installing the systems, and that could double by 2027.
"One of our values is being environmentally responsible, and (it's) always a good thing to let people know that, yeah, there may be a mound of trash sitting outside of Charlotte, in Concord, but there's, there's some pretty good purpose that can be derived and driven from it," Ginn said.
While capturing landfill gas is a good solution, the best climate defense ultimately may be keeping food and other organic waste out of the landfill in the first place, said NC State's Panzarella.
"That's what's producing the methane through its decomposition," he said. "This organic matter could be composted. And, and then at the end of that process actually you could have something that could be used as fertilizer."
Reducing waste also could extend the life of landfills, he added.
Federal climate scientists say increases in atmospheric methane have set records the past two years. They say finding more ways like these to reduce methane emissions are critical to slowing global warming.