Geologists map rocks to soak CO2 from air

March 6th, 2009 - 4:09 pm ICT by ANI  

Washington, March 6 (ANI): In a new report, geologists have mapped large rock formations in the United States that can also absorb carbon dioxide (CO2), which they say might be artificially harnessed to do the task at a vastly increased pace.
The report, by scientists at Columbia University’’s Earth Institute and the U.S. Geological Survey, shows 6,000 square miles of ultramafic rocks at or near the surface.
Originating deep in the earth, these rocks contain minerals that react naturally with carbon dioxide to form solid minerals.
Earth Institute scientists are experimenting with ways to speed this natural process, called mineral carbonation.
If the technology takes off, geologic formations around the world could provide a vast sink for heat-trapping carbon dioxide released by humans.
According to Lead author Sam Krevor, a graduate student working through the Earth Institute’’s Lenfest Center for Sustainable Energy, the United States” ultramafic rocks could be enough to stash more than 500 years of U.S. CO2 production.
Conveniently, most of them are clustered in strips along the east and west coasts, some near major cities including New York, Baltimore and San Francisco.
“We”re trying to show that anyone within a reasonable distance of these rock formations could use this process to sequester as much carbon dioxide as possible,” said Krevor.
Ultramafic rocks generally form in earth’’s mantle, starting some 12 miles under the surface and extending down hundreds of miles.
Bits of these rocks-peridotite, dunite, lherzholite and others - may be squeezed to the surface when continental plates collide with oceanic plates, or, less often, when the interiors of continents thin and develop rifts.
Because of their chemical makeup, when the rocks are exposed to carbon dioxide, they react to form common limestone and chalk.
A map accompanying the report shows that most such rocks are found in and around coastal mountain ranges, with the greatest concentrations in California, Oregon and Washington, and along the Appalachians from New England to Alabama.
Some also occur in the interior, including Montana. Worldwide, other formations are scattered across Eurasia and Australia.
The major drawback to natural mineral carbonation is its slow pace: normally, it takes thousands of years for rocks to react with sizable quantities of CO2.
But, scientists are experimenting with ways to speed the reaction up by dissolving carbon dioxide in water and injecting it into the rock, as well as capturing heat generated by the reaction to accelerate the process.
“It offers a way to permanently get rid of CO2 emissions,” said Juerg Matter, a scientist at Columbia’’s Lamont-Doherty Earth Observatory, where a range of projects is underway. (ANI)

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