Geologists Say Rock Laid Bare Under Omani Desert Can Absorb 4 Billion Tons Of CO2 a Year

180px-Perid_SanCarlos.jpgPetroleum Development Oman, the state owned oil company of Oman (partly controlled by Shell), is in discussions with geologists who claim they’ve found a type of rock that can be used to soak up huge quantities of carbon dioxide.
The rock, known as peridotite, is layered just under the surface of a desert in Oman. The peridotite was found to react chemically with CO2, forming solid minerals. What’s more, it absorbs hot water infused with a concentration of CO2 that engineers can drill deep into it.
Theoretically, the peridotite in Oman alone could take in 4 billion tons of atmospheric carbon a year and transform it into marble and limestone. Total global annual carbon emitted is around 30 billion tons.
In most places in the world, peridotite usually resides some 20 kilometers or more below the earth’s surface. But in Oman, it’s been pushed upwards due to geologic activity making it far more accessible.

Previously, scientists had assumed that peridotite formed by a process unconnected to the atmosphere and that the veins of peridotite are almost as old as the 96-million-year-old Omani rock encompassing it. But the Omani project dated the underground carbonate mineral veins back to 26,000 years on average. That means that the rock is still actively absorbing CO2. As a matter of fact, the peridotite naturally absorbs 10,000 to 100,000 tons of CO2 every year.
Similarly large exposures of peridotite are known on the Pacific islands of Papua New Guinea and New Caledonia, and along the coasts of Greece and the former Yugoslavia; smaller deposits occur in the western United States and many other places.
Engineers simply have to drill a hole and inject heated water containing pressurized CO2 in it. By injecting water in this manner, the absorption process is sped up 100,000 times and more. The naturally generated heat would further speed up the chemical reaction because large portions of rock would be fractured creating even more space for CO2 reactions. Plus, the further down the process takes place, the higher the temperature due to heat generated by the earth itself. It’s one of the more perfect carbon traps around.
“This method would afford a low-cost, safe and permanent method to capture and store atmospheric CO2,” according to geologist Peter Kelemen, who co-authored a paper about the project. Kelemen and his colleagues have filed patent papers for the method. But the geologist warns that their find doesn’t have guaranteed silver bullet potential. “We see this as just one of a whole suite of methods to trap carbon. It’s a big mistake to think that we should be searching for one thing that will take care of it all,” Kelemen points out.
One unknown side effect is that the cracking and expansion of the underground substances might produce localized micro-earthquakes. Yet Kelemen reassures us that this activity would not be perceptible to humans.
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