Oregon coast may be ideal spot to bury CO2

An underwater volcanic ridge off the coast of Washington and Oregon represents a potentially optimal site for ditching carbon dioxide, a group of Columbia University earth scientists has concluded. For one, the underwater basalt – or dried lava spewed by a subsea volcano – has the unique property that it could help convert injected CO2 into calcium carbonate, which is basically chalk. Storing it as a solid adds assurance that the carbon dioxide won’t escape and leak into the atmosphere.

To add to the security of storing much of the CO2 as a solid in the ridge, the Lamont-Doherty Earth Observatory researchers point out that gravity helps keep CO2, which at those depths is denser than sea water, from escaping back into the atmosphere. The ridge, called the Juan de Fuca plate, is within a few hundred kilometers of Oregon, Washington, and Vancouver Island. Total storage area estimated for the ridge is 208 gigatons of CO2, and it could be more if all of the CO2 is converted into calcium carbonate. The United States has an annual CO2 emission rate of 1.7 gigatons, so this site could in theory provide a century’s worth of carbon storage. Lead author David Goldberg, a geophysicist, also contends that the problem most commonly cited in relation to carbon sequestration – the trouble of transporting the carbon to a suitable storage location – can be surmounted in this case with relatively short pipelines from the coast.

Previous drilling studies showed that the rock in the Juan de Fuca plate had significant fissures to inject the CO2 into, and the area is believed to be seismically stable, so earthquakes are unlikely to change the geological profile of the area.

Generally, carbon sequestration involves injecting pressurized CO2 into a well that’s been drilled into porous rock. The CO2 is under high pressure as it travels through cracks in the rock, and in those conditions it turns into a fluid. Most US research is currently focused on land-based carbon storage, and some scientists are also investigating the possibilities of storing the greenhouse gas in depleted oil and gas fields.

The scientists published their conclusions last week in Proceedings of the National Academy of Sciences.