County, co-op unveil methane power plant at landfill

In Flathead County anyway, one man's trash is power for the rest of us.

Last Friday Flathead Electric Cooperative and Flathead County unveiled Montana's first methane-fueled power plant at the county landfill that could generate enough electricity for 1,600 homes.

"We're all making garbage," said county public works director Dave Prunty. "We have an asset in this landfill, now we have a resource, too."

As trash breaks down inside the landfill, the microorganisms that are feeding on it give off methane and carbon dioxide. Methane is extremely flammable, so much so that the state Department of Environmental Quality mandates that municipalities find some way to mitigate the buildup or seepage of the gas at landfills. Up until last week, that meant siphoning it out of the ground and piping it to a flare that burned it off round the clock.

Now those same wells that dot the landfill are pulling the gas toward the power plant instead.

Flathead Electric Cooperative, which owns the facility and is paying to operate it, received no-interest Clean Renewable Energy Bonds to construct the $3.5 million project, which includes an enormous Caterpillar generator.

"The board of trustees took a leap of faith and had a lot of foresight," said Cheryl Talley, a co-op spokeswoman.

Talley said that though the generator is capable of producing up to 1,600 kilowatt hours of power — figure 1kWh powers a home — but that the amount of methane coming out of Flathead County's relatively small landfill right now will limit it to about 900kWh.

The 41 wells that are sunk across the landfill are actually 6-inch permeated plastic pipes. Prunty said a 24-inch hole is drilled out — to within 15 feet of the bottom of the landfill — and then the pipe is inserted and the remaining space is filled with pea gravel. Then the pipe system is connected to a vacuum pump that coaxes the methane out of the surrounding trash, into the pipes and eventually to the generator. The pumps also keep the flammable gas from seeping out of the landfill into groundwater or neighboring properties.

Prunty said the power plants aren't uncommon in larger cities around the country, but that they're extremely unusual at small landfills like Flathead County's.

"It's one of a kind in Montana," he said. "It's really stepping out of the box for a landfill of our size."

Since Prunty said the county's landfill won't fill up for another 45 or so years, the co-op was sure to plan for all that extra methane when they built their power plant.

"There is room for a second generator," Talley said.