Underground rocks may turn carbon dioxide into harmless chemical

March 6th, 2009 - 1:53 pm ICT by IANS  

Washington, March 6 (IANS) Geologists have mapped large rock formations in the US that can absorb carbon dioxide and potentially be harnessed to vastly accelerate the process.
The report, by scientists at Columbia University’s Earth Institute and the US Geological Survey, shows 15,000 square km of ultramafic rocks at or near the surface.

Study co-author Sam Krevor, graduate student working through the Earth Institute’s Lenfest Centre for Sustainable Energy, said the US ultramafic rocks could be enough to stash more than 500 years of US’ carbon dioxide production.

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.

Conveniently, most of them are clustered in strips along the east and west coasts of the US - 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.

So-called carbon sequestration has become a hot area of research, but so far, most work has focussed on storing liquid or gaseous carbon dioxide underground where there is room: in saline aquifers, depleted oil wells and porous coal seams that are not commercially viable.

However, concern about leaks has scientists pursuing natural chemical reactions within the earth to turn the carbon back into a solid. Ultramafic rocks generally form in the earth’s mantle, starting some 18 km under the surface and extending down hundreds of kilometres, said a Columbia release.

Klaus Lackner, who directs the Lenfest Centre, helped originate the idea of mineral sequestration in the 1990s. The US survey is the first of what Lackner hopes will become a global mapping effort.

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