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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unpublished lab experiments currently being prepared for peer review, McGrail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.