Wednesday, February 11, 2015

Turning Carbon Dioxide Into Rock, and Burying It

A drilling rig at the CarbFix site in Iceland, where researchers are testing whether gaseous carbon dioxide can be turned into rock as a way of keeping it out of the atmosphere. (Credit: Bara Kristinsdottir for The New York Times) Click to Enlarge.
A $10 million project called CarbFix is developing an alternative way to store some of the carbon dioxide emitted by power plants and industries.  When that carbon dioxide is released into the atmosphere, it traps heat, making it the biggest contributor to global warming.  So to help stave off the worst impacts of climate change, experts say, billions of tons of CO2 may have to be captured and stored underground.
[Conventional carbon capture and storage] projects operate roughly the same way: carbon dioxide gas, highly compressed so that it acts like a liquid, is injected into a formation, usually sandstone and often an old oil or gas field.  Impermeable rock layers above the storage zone should, in theory, keep the CO2 trapped indefinitely, but because the gas remains buoyant, there is a risk that it will move upward through cracks and eventually bubble back into the atmosphere.

The CarbFix project differs from this conventional approach by using water along with carbon dioxide, and by injecting them into volcanic rocks.  The technique is designed to exploit the ability of CO2 to react with the rocks and turn into solid minerals.

But whether the approach will prove to be commercially viable and lead to wider adoption of carbon storage, particularly on the huge scale that will be required to help stem the forces of climate change, remains uncertain.
Mineral carbonation can occur in many kinds of rock, but often it is extremely slow. The CarbFix approach accelerates the process by injecting into basalt, a very reactive rock. ...

Large basalt deposits are found in other locales, including the Pacific Northwest in the United States.  There, at a site in the Columbia River basin near Wallula, Wash., a similar test project — the only other one in the world — is also in an analysis phase, having completed the injection of 1,000 tons of carbon dioxide in 2013.

The project, a partnership of several companies and Battelle Memorial Institute, a nonprofit research and development organization that operates the Pacific Northwest National Laboratory, might best be described as a hybrid between conventional CO2 storage and the CarbFix approach.

Only carbon dioxide is injected, said Pete McGrail, a research fellow at the laboratory who leads the project.  That helps to keep costs in line with conventional CO2 storage.  And the basalt has dense, impermeable layers that keep the buoyant gas contained.

But because basalt is so reactive, after a relatively short time — a matter of years, not centuries — most of the CO2 should be mineralized, making long-term monitoring unnecessary.  (With the CarbFix process, once the CO2 is dissolved in water, it is no longer buoyant, so there is no need for an impermeable layer.)

Read more at Turning Carbon Dioxide Into Rock, and Burying It

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