Could carbon-soaking rocks solve climate crisis?

Scientists seeking a cost-effective means of sequestering carbon dioxide using natural geological reactions were given a major boost last week when new research was released showing that the US alone has 6,000 square miles of rocks at or near the Earth's surface capable of naturally soaking up millions of tonnes of CO2.

The study from scientists at Columbia University's Earth Institute and the US Geological Survey found that there are large swathes of ultramafic rock in California, Oregon, Washington, and along the Appalachians, with smaller clusters also found in the interior, all of which are capable of sequestering carbon dioxide from the atmosphere through a natural process known as mineral carbonation.

The report's lead author, Sam Krevor, a graduate student working through the Earth Institute's Lenfest Center for Sustainable Energy, said that in theory these ultramafic rocks could store more than 500 years' worth of US CO2 emissions.

The process of mineral carbonation on ultramafic rocks such peridotite, dunite and lherzholite takes thousands of years for large quantities of carbon dioxide to be soaked up. However, the research team is now investigating techniques for accelerating the process, including dissolving carbon dioxide in water and injecting it under high pressure into the rock.

Juerg Matter, scientist at Columbia's Lamont-Doherty Earth Observatory, has recently undertaken research with his colleague Peter Kelemen in Oman that suggested such techniques could significantly accelerate the process by which carbon dioxide reacts with ultramafic rocks. A separate pilot study in Iceland involving basalt rocks is also scheduled to take place later this month, with researchers confident that it too could serve as a store for carbon emissions.

Additional research is also ongoing to map the global availability of suitable basalt and ultramafic rocks.

Krevor said that with many of the US rock formations found near major cities, technical innovations could make it possible for the gas to be captured from power plants and other industrial facilities sequestered in the rocks. "We are 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.