Newest Weapon Against Climate Change: Rocks

Rocks with a powerful thirst for carbon dioxide (CO2) could suck enough of the greenhouse gas from the atmosphere to help counteract global warming, according to a recent study.

The country of Oman hosts a strip of mantle rocks called peridotites in a formation 350 kilometers (217.5 miles) long and 30 kilometers (18.6 miles) wide.

Formed under searing heat and crushing pressure deep in the Earth, the rocks have unusual chemical properties when thrust up to the surface, including an affinity for carbon dioxide.

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"They are in disequilibrium with the surface," Juerg Matter of Columbia University said. "So they react really quickly with the atmosphere, rainwater and groundwater, and absorb CO2."

Traditionally, scientists have thought the process is self-limiting, stopping as newly-formed carbon minerals filled up spaces in the rocks.

But recently, Matter and a team of scientists have discovered that the usually gray rocks are laced with ribbons of red. These bands were produced by a mineral called listwanite, formed when the minerals in peridotite are carbonized.

If all of the mantle rocks exposed in Oman were converted in this way -- a highly improbably scenario, the team admitted -- they would lock away 4,000 years worth of human emissions.

Even a small fraction of that could make a dent in carbon dioxide levels in the atmosphere. Globally, peridotites occur in large enough amounts that carbon sequestration programs would make sense in places like Greece, Papua New Guinea and the west coast of the United States.

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"This is one option, and there are lots of options for carbon sequestration," Matter said. "The most interesting part about this is it leads to permanent storage of CO2. You don't have to worry about leakage if you lock it up as a mineral instead of storing it in a reservoir or aquifer."

The team noted that listwanite is riddled with fractures, which increase surface area and allow CO2-rich groundwater to keep circulating within the rock. They believe mimicking such a process would be key to the success of any man-made attempts at carbon sequestration using peridotites.

Matter and his team will present their latest findings next month at the annual meeting of the American Geophysical Union in San Francisco.

"What's really new here is that these reactions are occurring at lower temperatures and faster than was previously thought," Gregory Dipple of the Univeristy of British Columbia said.

Dipple cited his experience at a large mine in Australia, where peridotite tailings were sucking up as much as 50,000 tons of dioxide each year from the atmosphere. The mine's annual emissions were around 350,000 tons.

"You know, the tailings are offsetting something like 15 percent of emissions just by sitting there," Dipple said.

He added that peridotite's global capacity to sequester carbon dioxide is "almost infinite," but that he, Matter and other researchers are still several years from the first attempts to engineer such a solution to global warming.