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A climate change solution?

Beneath the Columbia River Basin, a real-life trial of the uncertain science of carbon sequestration – Part I


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George Peridas, a science fellow with the Natural Resources Defense Council, supports geosequestration in general, saying that "with rigorous regulatory controls, we are confident that sequestration can work very well without endangering health or the environment." He thinks McGrail's research worthwhile, although he's not ready to treat it as "a high confidence scenario." Peridas is concerned that the columnar joins and other crack networks that allow CO2 to travel into porous areas of the basalt will also allow it to come back out. Monitoring may also be a problem. For example, Peridas says, when seismic signals are used to determine underground structures, "in the data you get back it's hard to distinguish between the CO2 and the rock itself."

Nick Riley, a geosequestration researcher for the British Geological Survey, says, "My take on this is that the (chemical) reactions are too slow. I also think it will be difficult to get the rock to receive the CO2 at the rates required." But McGrail has reason to differ. In unpublished lab experiments currently being prepared for peer review, McGrail and his team put small amounts of basalt into a vessel with CO2, heating and pressurizing the samples to levels representing conditions deep underground. The carbonate minerals, he says, formed in "weeks to months."

"We really did not expect this," McGrail says. "It was pretty close to serendipity."

Such rapid transformation is orders of magnitude faster than the rate of similar reactions in sedimentary rocks, which can take tens to thousands of years to fix injected carbon dioxide into solids. Since the trick is to keep the liquid CO2 buried long enough for the chain of chemical reactions to immobilize it, basalt's processing speed is one of its strongest assets in the carbon sequestration race.

A 2005 Intergovernmental Panel on Climate Change report on geosequestration estimates that the world's deep saline formations could handle over a trillion tons of CO2. The Columbia basalt, however, may only be able to absorb a hundred billion tons, and McGrail has an even more conservative estimate of 20-50 billion tons. Fossil fuel emissions are putting about 26 billion tons of CO2 into the atmosphere every year, and the figure is rising. So if the Columbia basalt were the planet's sole repository of captured CO2, it would likely fill up in a couple of years.

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