Garbage to gas

Landfills and sewage treatment plants are an overlooked source of clean energy - but a boom in biomethane might be coming.

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What was once the I-95 landfill near Lorton, Virginia, is now dozens of acres of rolling green fields – dotted by more than 200 metal pipes emerging from the grass.

The pipes are wellheads for natural gas, and they are collecting the methane generated by more than 10 million tons of decomposing garbage dumped by Washington, D.C.-area residents over the course of 30 years.

A vacuum pump draws the gas from underground, through the wellheads, and connects it to roughly 14 miles of pipeline that run throughout the landfill. Under each wellhead, says Mike Malfitano, an environmental technical specialist for Fairfax County, “there’s a three-foot bore hole that goes 110 feet down into the waste mass.”

Although it closed in 1995, county officials expect the landfill to keep emitting gas for at least the next decade. On its best days, says Fairfax County environmental engineer Chris Meoli, the landfill generates 2,000 cubic feet per minute of gas – enough to create 4.9 megawatts of electricity. It’s more than enough to power the Noman M. Cole wastewater treatment plant three miles down the road, saving the county as much as $500,000 a year in power costs, according to a 2015 county report. What’s left over is sold to the grid.

According to the Environmental Protection Agency (EPA), landfills are among the nation’s largest sources of methane, accounting for nearly one-fifth of all methane emissions generated by human activity in 2012. That’s why advocates of landfill gas projects like the one in Fairfax County say these efforts have enormous environmental benefits – first, by capturing harmful methane emissions that would otherwise contribute to climate change and second, by replacing more carbon-heavy fuels for power and transportation.

Moreover, there’s no shortage of garbage. According to the group Energy Vision, Americans dump about 250 million tons of municipal solid waste per year – including 70 million tons of food and yard waste. It’s a clean energy opportunity the nation is literally throwing away.

Advances in waste management, along with recent changes in federal and state policy, are now prompting a potential boom in bio-methane opportunities – not just involving landfills but sewage treatment plants, dairy farms and other sources of organic waste. Companies are also showing greater interest in renewable natural gas as an alternative to gasoline and diesel, further stoking interest and demand.

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