One of coal miners' deadliest enemies, highly flammable methane, could provide the United States with at least a 20-year natural gas supply, researchers say.

Methane - a colorless, odorless and volatile gas - forms naturally when plants and other organic matter decompose. It also is produced and trapped in underground coal and petroleum deposits.The presence of methane in a mine poses a constant danger because of the potential for explosion, said Joseph Hucka, a University of Utah professor of mining engineering.

"However, because methane is a clean source of energy and environmentally acceptable, it has the potential to become a major energy source easier to produce than other fuels available in large quantities," Hucka said.

In addition to its use as a fuel, methane also is important as a source of organic chemicals, carbon black and hydrogen.

The U.S. Bureau of Mines estimates more than 300 billion cubic feet of methane is released daily into the atmosphere from the nation's coal mines.

Mineable coal beds alone contain up to 400 trillion cubic feet of trapped methane, Hucka said. And the Gas Research Institute of Chicago claims America's known coal reserves may contain as much as 800 trillion cubic feet of methane.

"Recovery of only half that amount could provide the nation with a 20-year supply of natural gas, at current consumption rates," he said.

That doesn't mean homes and factories would be heated with methane, he said, but coal mining companies could use the gas for heating, drying coal, and running turbines and company vehicles.

"The first who could benefit from it is the coal company," Hucka said, and that would free the gasoline, fuel oil or electrical energy supplies they are using for other consumers.

Hucka and David Bodily, associate dean of the University of Utah's College of Mines and Earth Sciences, received a $200,000 Energy Department grant for a three-year study of how methane gas forms and remains in coal beds in western U.S. mines.

"To cope with the problem of gassy mines, it is imperative researchers improve their understanding of how methane forms and is retained in coal beds. We must develop a better grasp of the phenomenon of methane migration in coal beds," Bodily said.