The peridotite solution

Here’s a remarkable sequestration mechanism that seems ideal for our needs. A single wedge, even a single site solution.

The researchers have shown that rock formations called peridotite, which are found in Oman and several other places worldwide, including California and New Guinea, produce calcium carbonate and magnesium carbonate rock when they come into contact with carbon dioxide. The scientists found that such formations in Oman naturally sequester hundreds of thousands of tons of carbon dioxide a year. Based on those findings, the researchers, writing in the current early edition of the Proceedings of the National Academy of Sciences, calculate that the carbon-sequestration rate in rock formations in Oman could be increased to billions of tons a year–more than the carbon emissions in the United States from coal-burning power plants, which come to 1.5 billion tons per year.

The researchers found that the natural peridotite formations in Oman captured carbon dioxide in a network of underground veins. Peridotite contains large amounts of olivine, a mineral composed of magnesium, silicon, and oxygen. As groundwater reacts with the olivine, the water becomes rich in dissolved magnesium and bicarbonate, with the latter effectively increasing the carbon concentration in the water by about 10 times. As this water seeps deeper into the rock and stops reacting with the air, the magnesium, carbon, and oxygen precipitate out of solution and form magnesium carbonate, also called magnesite. Dolomite, which contains calcium, magnesium, carbon, and oxygen, also forms. As the magnesite and dolomite form, they increase the total volume of the rock by about 44 percent, causing cracks to appear throughout it, which creates a network of fractures as small as 50 micrometers across. This opens up the rock and allows water to penetrate further. “It’s a little bit like setting a coal seam on fire,” says Peter Kelemen, a professor of earth and environmental studies at Columbia University. “You’re taking rocks that haven’t been exposed to the atmosphere, and you’re oxidizing them very fast.”

Many a slip twixt cup and lip of course, but (to scramble metaphors) maybe there is a silver bullet after all. I’d love to see this work at scale. Most of the commenters on the linked Technology Review so far tend to disagree, choosing to worry about the local ecosystem. How do In It readers feel, I wonder?

Update: Here’s the peer-reviewed article that Tech Review ought to have cited, with thanks to David Benson.

Update: Here’s a similar article at Popular Mechanics.