The product of coal gasification—a process that turns coal into a gas rather than burning it directly—is another type of unconventional gas that has recently moved into the spotlight. Coal gasification has been around for almost a century but climbing energy prices and growing climate change concerns are now giving the technology a push. “Gasification can allow us to utilize coal in an environmentally friendly way,” said Ian Duncan, associate director for environmental programs at the Bureau of Economic Geology.
The technology could play an important part in the U.S. energy future because the country has a huge supply of raw material. “We have about 50 percent more energy resources tied up in coal than the Middle East has in oil,” Duncan said. In the gasification process pulverized coal is introduced into a reaction chamber with small amounts of oxygen and steam. At temperatures of about 2,500 degrees C (4532 degrees F) and pressures 1,000 to 2,000 times higher than atmospheric pressure the coal breaks down into its chemical building blocks and produces a synthetic gas, which consists mainly of hydrogen and carbon dioxide. The hydrogen gas is then fired in gas turbines to generate electricity. Even though the technology drastically reduces emissions of nitrous and sulfur oxides, heavy metals, and particulate matter, it still spews out carbon dioxide. “To make it a near zero-emissions energy technology, the carbon dioxide needs to be sequestered,” Duncan said.
Whether or not coal gasification could become economically feasible depends on a host of parameters, including what the future regulatory framework with respect to carbon emissions will look like, said Michelle Foss, chief energy economist and head of the Bureau of Economic Geology’s Center for Energy Economics. “Capturing emissions would add a pretty substantial cost to the process.”
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