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Turning Landfill Methane into Power

Every week groups from close by and around the world tour a landfill facility in DeKalb County to see a huge example in the latest technology that is turning trash into clean energy and an income source.

DeKalb County operates one of the United States’ largest permitted municipal landfills, and the methane released by decomposing organic waste was a potential energy source the county wanted to tap into. So the county developed a green energy project to capture the methane and burn it to generate electricity.

Billy Malone, DeKalb County director of sanitation, explains that after drilling into the massive hillside, dozens of pipes allowed methane to be drawn into a facility where two Cat® G3520C landfill gas low-emission generator sets burn it and generate 3.2 megawatts of electricity per hour, which a Cat®XLM2 utility paralleling switchgear puts up on the grid. That’s enough electricity to power about 3,000 homes.

“The electricity goes to a substation about a mile and a half away, and then into homes where moms and dads can read to their children with light made from their garbage,” Malone says.

The project has succeeded both financially and environmentally. The DeKalb County Public Works Department, Division of Sanitation invested $5 million in the Seminole Green Energy Project and is selling electricity for about $100,000 per month. After five years the project had paid for itself and was generating a profit for the sanitation division. Environmentally, the project will offset fossil fuel greenhouse gas emissions of 17,100 metric tons of carbon dioxide equivalents per year, the equivalent to removing emissions from 3,300 vehicles from roads, reducing oil consumption by 40,000 barrels, or planting 4,700 acres of forest. Georgia Power says the more electricity that is generated from sources like methane, the less needs to come from other sources like coal and other fossil fuels. Landfill gas is the only renewable form of energy that directly reduces the amount of pollution released into the atmosphere.

Additionally, the Caterpillar equipment held NOx emission levels at half the level allowed by the Georgia Environmental Protection Division permit.

The project has earned sanitation division awards from the Solid Waste Association of North America (SWANA).

Outside, the 1,100-acre landfill itself is one of the first impressions that millions of people have of Atlanta every year. The flight path for planes landing at Hartsfield-Jackson Atlanta International Airport takes them directly over the Seminole Road facility—the only landfill operated by DeKalb County. Every day, some 2,000 tons of waste materials arrive, some disposed and some recycled on site, but people looking down from arriving planes don’t see acres of refuse. Instead, they see a grassy hillside with a gazebo on top, several areas of manicured Georgia clay, and one smaller area where operators are using Caterpillar compactors and excavators along with D6 and D8 dozers to compact and cover that day’s garbage.

At the base of the landfill is a “liner” constructed of clay covered with 60-mil plastic and covered with two feet of sand. By the end of each day another 2,000 tons of waste has been delivered, bulldozed into place, compacted, and covered with six inches of dirt, so that no garbage is visible and no smell detected by nearby residents.

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