Researchers studying peridotite rock in the Middle Eastern country of Oman say the material could be an amazing absorber of carbon dioxide.
Peridotite is found in abundance in the Earth's mantle, about 12 miles down and under the Earth's crust. Large chunks of the rock make their way to the surface as the crust moves and shifts. While the scientists making the discovery studied a large field of peridotite in Oman, the material can be found in various places around the globe, including in the US
The study, which will be published in the Proceedings of the National Academy of Sciences, shows that peridotite reacts with CO2 at surprisingly high rates. The reaction forms a solid carbonate like limestone or marble. Researchers involved in the study feel that the process can be sped up to even higher rates with drilling and injection of CO2 into the rock.
"This method would afford a low-cost, safe and permanent method to capture and store atmospheric CO2," said geologist Peter Kelemen, lead author of the study. Keleman estimates that the Omani peridotite field, which is about the size of Massachusetts, is naturally absorbing between 10,000 and 100,000 tons of CO2 every year.
Although scientists have long known that peridotite will react with CO2, plans to transport it to power plants where it could be exposed to smokestack gasses proved unwieldy or too expensive. But the extremely high reaction rates occurring naturally means that CO2 could instead be shipped to peridotite sites to be absorbed, and at a much lower cost.
By simply boring into the surface of exposed peridotite and pumping in heated water that is saturated with pressurized CO2, researchers are confident the reaction process can be increased 100,000 times or more. Through this process, scientists predict that the Omani peridotite field alone can absorb about 4 billion tons of CO2 annually, which equates to about 13 percent of the total amount humans send into the atmosphere.
One possible drawback – the cracking and expansion of peridotite deep under the Earth's surface from pressurized CO2 and from the formation of new carbonates could result in micro-earthquakes. But Kelemen said they would be nearly imperceptible.