Deadly Methane Is Viewed as Source of 20-Year Energy Supply
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.
Source of Hydrogen
In addition to its use as a fuel, methane is also 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 reports that 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 does not mean homes and factories would be heated with methane, he said, but coal 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 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.
“When coal is mined and broken into finer particles, the absorbed part of methane escapes into open areas of the mine,” Hucka said. “To prevent an explosion, the mine must be ventilated, which increases mine operating costs.
‘Improve Their Understanding’
“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.”
Added Bodily, “We want to know whether the pore structure of coal, the degree of coal maturation, the geologic strata of the mine or combinations of these and other possible factors determine the amount of gas in a mine.”
To protect underground miners, Bodily said, “the ideal situation would be to degas the coal bed before excavation actually begins.” Capturing that released gas could result in a significant energy source.
The researchers will collect coal samples in the Book Cliffs, Wasatch Plateau and Emery fields in east-central Utah and in the Dutch Creek Mine in Colorado. Colorado coals contain significant amounts of methane, they said, while the methane content in Utah coals varies greatly.
With the assistance of Utah Geological and Mineral Survey geologists, they will collect coal from underground seams. They also will extract coal samples using a special device that collects specimens from horizontal bore holes.
As part of the study, the methane content and its release rate will be compared with the physical and chemical properties of coal samples and the geochemical and geological history of coal seams.
The first problem, Hucka said, is solving the puzzle of why mines with similar kinds of coal often produce different amounts of methane. And the next problem is unlocking and extracting the gas from underground deposits.
“We should tap this energy source. We should take advantage of it because it must be removed for safety reasons,” Hucka said. “It’s going to be taken out of the mines anyway, so why not take advantage of it?”
Means of Reaching Methane
Bodily said the researchers are looking at four means of reaching the methane in underground coal deposits.
In areas where coal seams are not being mined, two types of holes can be drilled from the surface into deposits--a vertical hole and a flexible bore hole where the drill bit goes down in a vertical direction and then bends to run the length of horizontal coal seams.
In working mines, bore holes can be drilled directly into the coal face or at a slant into areas above or below the seam to siphon off the gas.
Water is pumped into holes drilled into the coal seam and then pressurized to fracture the deposits and allow more gas “to drain” into the bore hole, Hucka said. “This way we can expose a much larger area.”