Valdosta Daily Times

May 11, 2014

The Power of Trash: Gas-to-Electricity Plant online at Pecan Row

Stuart Taylor
The Valdosta Daily Times

VALDOSTA — One man’s trash is another man’s treasure, or in this case, one landfill’s trash is the fuel to produce enough power to run 2,000 homes a year.

As trash decomposes, it emits gases. The methane gas released by a large-scale landfill is a potential power source.

It was a year-long process to convert Advanced Disposal’s Pecan Row Landfill into a gas-to-electricity facility. A high-density polyurethane composite liner was rolled across approximately 72 acres of Pecan Row.

The liner serves a few purposes. It seals the landfill, keeping further moisture and rainwater from seeping in and helps increase the amount of methane collected. Aesthetically, it acts as a foundation for the two feet of compacted clay being added on top of it. Grass will follow, turning mountains of refuse into green, rolling hills.

The liner is extensively quality tested to ensure the best seal before covering it. Sixty gas wells have been drilled throughout the landfill.

The wells are hooked into lateral connection lines that snake throughout Pecan Row. A 200-horsepower blower at the conversion plant keeps a constant vacuum on the landfill, pulling in the gas.

The collected gas goes through several vessels designed to clean it, pulling out hydrogen sulfides — which can be hard on the plant’s engines — and anything else that’s not methane gas.

The methane is chilled, lowering the temperature to pull the moisture from it. This allows for a better burn.

The plant has three engines, each one burning approximately 600 cubic feet of methane per minute.

“It burns pretty clean, not a lot of emissions,” said Advanced Disposal General Manager Greg Walk. “Methane is methane. It’s the same as natural gas.”

While Advanced Disposal owns Pecan Row, Energy Systems Group owns the plant, selling the power straight to Green Power EMC’s electric grid.

The plant went online in December. By January, operators found it was producing 20 percent more gas than expected, most likely due to the capturing effects of the liner.

The plant is expected to generate 4.8 megawatts of power, enough to power roughly 2,000 homes.

“It’ll produce gas for about 30 years,” said Walk. “It’s on a curve. It’ll peak out in about 10 years and start declining.”

Plans are already underway to design and implement the same conversion process for the nearby Evergreen landfill. To add Evergreen, the conversion plant would have to expand slightly, adding room for a fourth engine.

This addition to the conversion plant could extend its life by decades. Eventually the Evergreen landfill will also run out of gas, but that’s in the future.

“The plant could be here 40 or 50 years,” said Walk.