Converting waste into wattage

Nov 14 - McClatchy-Tribune Regional News - Tiffeny Owens The Decatur Daily, Ala.

The Decatur-Morgan County Regional Landfill on Alabama 20 is not just in the trash business anymore.

For more than a year now, decades-old rotting garbage has been converted into methane gas, then electricity for the Tennessee Valley Authority's power grid.

Each day, around a million cubic feet of methane, a greenhouse gas, is captured before it can escape into the atmosphere. The city also is getting paid for helping generate this renewable energy source, to the tune of $60,000 annually for the sale of methane and $20,000 for the sale of electricity.

It stands to save another $15,000 to $20,000 this winter by heating its new recycling facility with hot water produced by its 1-megawatt methane-powered generator.

"Landfills are one of our most untapped resources for renewable, clean energy," said Tommy Orr, who operates Grainger's methane-to-electricity generator on site at the landfill.

Grainger collects methane gas pumped from 115 wells, which began drawing out gas from the landfill in 2004, and uses it to run the 1-megawatt engine that generates electricity. That power is then sold to TVA through Joe Wheeler Electric Membership Cooperative.

"It comes into us dirty and wet," Orr said of the landfill gas. "We clean it, dry it and cool it. Then its ready to use as a natural gas fuel for the two generators, one here at Grainger and the second one at the recycling center."

Grainger's generator began producing power in July 2010. A year later, the recycling center's generator came online. The city gets paid for the methane Grainger uses in its engine and for the power created by the one at the recycling center, said Rickey Terry, landfill director.

"After the first generator was installed, we could see that the landfill was producing enough methane to power a second. That's when we added the one at the recycling center, which was being built around the same time," Terry said.

Terry said the revenues from both generators go back into the landfill's budget, which the city classifies as an enterprise fund, meaning it's self-sustaining with every dollar coming in required to be reinvested in operations.

He said this year's budget is the tightest one he has seen, comparing revenues to expenses, which makes the income from the two generators that much more important. Officials project $4.9 million in landfill revenues for fiscal 2012, down from the $5.9 million in fiscal 2011.

"There's a lot of money to be made on methane produced by landfills," Orr said. "It can be sold at a cheaper rate than other natural gases, but like with all these renewable energy processes, it has to be cost effective to become widespread."

Companies passionate about reducing their environmental impact are opting to pay more to support renewable electricity creation through TVA's Green Power Switch program. This "green" electricity costs more to produce than traditional power generated by cheaper, but "dirtier" sources such as fossil fuels.

But for every $4 block of "green power" that companies purchase, TVA guarantees 150 kilowatt-hours of electricity is generated by a renewable resource in the Tennessee Valley. And once it's produced and hits TVA's power grid, there's no difference between it and the electricity created from non-renewable sources. Decatur, Hartselle and Athens Utilities, along with Joe Wheeler EMC, participate in the program.

So, the next time you're driving down Alabama 20 past the landfill, Orr invites you to stop in and see the energy conversion process in action.

"We do tours almost every day," he said. "People are amazed when they learn how their trash becomes power."

How garbage becomes electricity

Extracting methane from garbage and using it to generate power is a complex process. Below are the basics:

--Trash is covered at the Decatur-Morgan County Regional Landfill and left to decompose for years underground.

--Wells are dug deep into the levels of trash and pull methane and carbon dioxide gases released from the rotting trash.

--The gases are pumped into Grainger's facility where methane is separated and cleaned.

--Methane then fuels an engine that spins a generator, which creates electricity. Grainger's generator produces around 900 kilowatts per hour.

--The power is then fed to Joe Wheeler EMC's grid, which connects to TVA's power grid.

w w w . w a s t e r e c y c l i n g n e w s . c o m