More than $250,000 a year - for years - had been going up in flames at the Ada County landfill.

But for the past two years, the county has been turning trash into cash and into enough electricity to power a small town.

"It is a win-win-win situation," said Fred Tilman, Ada County Commission chairman.

Federal requirements and safety concerns require the county to get rid of its landfill-produced gas - a mostly methane and carbon dioxide byproduct of decomposing solid waste.

But instead of burning it off, as it used to do, the county has tapped it as a renewable energy source. And because a private company is converting the gas into electricity, it costs the county nothing to run the system, Tilman said, and the county's share of the profits keeps increasing.

FROM NUISANCE TO RESOURCE

Landfills and livestock are the two largest human-related sources of methane in the U.S., according to the Environmental Protection Agency. Each accounts for about 23 percent of all human-related methane emissions.

If it is not captured, landfill methane becomes a greenhouse gas at least 20 times more potent than carbon dioxide, the principal greenhouse gas.

Uncaptured landfill gas also poses a threat because it can contaminate groundwater or even explode.

Because of the danger to safety and health, municipal landfills are required to capture and destroy the harmful gas. In Ada County, the gas was collected and burned off in a flare.

When Tilman first became a commissioner, one of his first official duties was to go to the landfill and cut the ribbon on the two big flares that burn off landfill gas.

"I was so amazed standing there when they fired those things up. As I watched millions of BTUs going up in the air I thought, what a waste. That is what prompted me to say 'We've got to be able to figure out how to do something with that,' " Tilman said.

$600,000 IN REVENUE AND COUNTING

In late 2006, the county partnered with Georgia company G2 Energy LLC, which purchased and installed two engines at the landfill to convert the gas into electricity.

Earlier this year, G2 was purchased by Fortistar, which owns more than 50 landfill power plants across the U.S. and represents about 12 percent of the landfill gas-to-energy market.

The company sells the energy to Idaho Power, according to Dave Neal, director of Ada County's solid waste management department. Each engine generates about 1.6 megawatts of electricity - enough to power 2,400 average homes.

The company owns and operates the equipment, so all the county must do is divert the gas from the flare to the engines.

"Not only has it not cost us anything, but over the last two years the county has received about $600,000," Tilman said. "It has been a terrifically successful project. I fail to see a downside to it."

Fortistar pays the county 89 cents for every 1,000 BTUs of gas it takes from the landfill. In addition, Fortistar gives the county 40 percent of the annual tax and green credits the company receives for the project.

The money goes back into the county landfill, which is a self-supporting department funded by fees, not property taxes.

In 2007, the project's first year, the engines ran at 75 percent capacity while the system was fine-tuned. The company paid the landfill $266,147 - $157,872 in gas sales and $108,276 in tax and green credits.

In 2008, the machines ran at full capacity, and the landfill received $334,346 - about 2 percent of the landfill's total revenue - for selling the nuisance gas that otherwise would have been burned up in the flare or polluted the environment.

Currently, the landfill gas is collected via a network of 88 wells and several miles of pipes. The county needs to add more wells as the landfill expands. Soon, the county may collect enough gas to bring on a third engine, which could generate another 1.6 megawatts of electricity and another $150,000 a year for the landfill.

"It is quite the mining operation up there," Tilman said.

Ada County is the only landfill in Idaho converting its methane gas into electricity. More than 400 landfills around the country are doing the same thing.

"All landfills produce gas. They all should consider doing this," Neal said.

Like landfill gas, sewage gas generated at wastewater treatment plants is primarily methane and must be captured and destroyed. It, too, can be converted into electricity.

Boise burns off much of its sewage gas, but it wants to start converting it to electricity within the next five years, said public works director Neal Oldemeyer. The city plans to install a 1-megawatt generator at its West Boise wastewater treatment plant and sell the electricity to Idaho Power.

The city already uses some of its captured sewage gas to operate some of the equipment and to heat some of the buildings at both the West Boise and Lander Street plants.

Cynthia Sewell: 377-6428