Monday, September 15, 2008

Burning coal in the ground to create gas looks promising to India, China; several pitfalls remain

Underground coal gasification, or burning coal in the ground to produce natural gas, "has the potential to tap enormous and otherwise inaccessible coal reserves -- and to slow the speed of climate change," David Winning reports in The Wall Street Journal. India and China "are investigating large-scale commercial projects ... building on pilot projects in the U.S. and elsewhere," writes Winn, the Beijing editor of Dow Jones Newswires. "The two countries are also looking at the possibility of capturing and permanently storing underground the gases produced, like carbon dioxide, which scientists believe cause global warming."
The Soviet Union pioneered the technology in the 1930s, and a power plant in Uzbekistan still uses it. "Now, thanks to higher oil and gas prices, underground coal gasification has again become cost-competitive," Winning reports. "Advances in the technology also make the practice more attractive. ... Underground gasification also presents an attractive alternative because it produces no sulfur oxide or nitrogen oxide, there are lower levels of mercury and particulates, and the ash stays underground. Experts say the technology is especially suitable for low-rank coals like lignites and sub-bituminous coal, which produce less heat when burned due to their high ash content, and are highly polluting."

There are, of course, major concerns about water pollution or land subsidence caused by "cavities created when the coal seams are drilled and burned out," Winning writes. Advocates say water can be protected by managing pressures in the coal seam, and subsidence can be avoided by choosing a site with strong rock layers. And what about the main concern about coal projects? "A large-scale project that includes carbon capture and sequestration ... is still years away," Winning reports. "The big hope is that carbon dioxide produced in the process can be pumped back into the void left by the combustion of the coal underground, and permanently sequestered from the atmosphere, helping to reduce the emission of greenhouse gases. But ... carbon capture would likely make underground gasification more expensive." (Read more)

No comments: