Global Warming Rocks

November 28th, 2008 | Sources: Economist, PNAS


Geologists know that when carbon dioxide contacts the igneous rock peridotite, a spontaneous chemical reaction results. The reaction produces limestone and eliminates carbon dioxide.

Carbon dioxide is a greenhouse gas, so people thought why not grind up some peridotite, transport it to power plants and line smokestacks with the stuff to trap CO2 before it’s released into the atmosphere?

A good thought, but one that proved too costly and energy intensive.

Now, a study published in the Proceedings of the National Academy of Sciences concludes that the miracle stone’s gas trapping abilities can be enhanced a million-fold by simple methods, and the whole CO2 sink idea suddenly has legs.

Peridotite normally resides in the Earth’s mantle 15 miles below the surface. Sometimes though, plate tectonic collisions push peridotite to the surface. That’s what happened eons ago in Oman which is now home to an exposed patch of peridotite the size of Massachusetts.

After 5 years of field work in the Omani desert, Peter Kelemen and Juerg Matter concluded that its peridotite patch is naturally absorbing 10,000 to 100,000 tons of carbon a year–far more than previously thought.

This means it may be feasible to pump CO2 from regional power plants to specially prepared peridotite fields resulting in “a low-cost, safe and permanent method to capture and store atmospheric CO2,” according to Kelemen.

The process would involve boring holes into the rock and injecting warm water containing pressurized CO2. Once started, the reaction would generate heat that would further accelerate the reaction. Fractures would form exposing new peridotite to the soda. The man-made gas trap would keep going as long as fresh CO2 was supplied.

The scientists assert that Omani peridotite alone can absorb some 4 billion tons of carbon a year—that’s 13% of the total spewed into the atmosphere each year.

Peridotite fields also exist in Papua New Guinea, Greece and Croatia. There are small deposits in the western United States as well.

And it turns out that ubiquitous basalt may have similar greenhouse gas gobbling characteristics. Scientists in Iceland are pursuing that lovely possibility right now.


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