Scientists may have found a way to chemically lock up a trillion metric tons of carbon dioxide, many times the expected global carbon emissions over the next century. The plan involves injecting the greenhouse gas into huge formations of the porous volcanic rock basalt that lie on the sea floor. The approach would be expensive, however, and a host of questions remain about the technique.
Scientists around the world are examining ways to permanently store vast quantities of carbon dioxide in geologic formations. The hope is that carbon emissions from power plants or factories can someday be sequestered instead of being emitted into the atmosphere. Until now, most small- or medium-scale studies have focused on underground aquifers or depleted oil or gas wells as possible storage sites. Although feasible, these reservoirs might have limited capacity locally and could cause environmental problems, such as leakage into ground water.
Now, researchers have detailed the potential for deep-sea basalt formations to provide even more places for humanity to quarantine its carbon waste. A team led by geophysicist David Goldberg of Columbia University's Lamont-Doherty Earth Observatory in Palisades, New York, focused on a 70,000-square-kilometer region of the Juan de Fuca plate. This honeycomb of porous basalt lies under more than 200 meters of clay roughly 200 kilometers off the Oregon coast. Analysis of drilling data along with geochemical and seismic studies reveal that this region alone could hold more than 250 billion tons of carbon dioxide--more than 120 years worth of U.S. carbon emissions.
In the group's scheme, reported today in the Proceedings of the National Academy of Sciences, carbon dioxide would be injected in a liquidlike state into the sea floor, where it would be held below the clay sediments for decades to centuries. There, the carbon would react with the basalt to form chalk, a chemical reaction that laboratory and field tests on terrestrial basalt formations suggest is irreversible.
Goldberg says the technique has "enormous potential," but he notes that a lot more research needs to be done. His team would like to conduct field trials, for example, to gauge potential leakage and other possible environmental side effects.
The approach is also likely to be costly, Goldberg says, requiring huge drilling platforms akin to oil rigs and hundreds of kilometers of pipelines. "It's going to require a much more significant infrastructure investment than other carbon-sequestration concepts," he says. But Goldberg thinks that the advantage of having the carbon dioxide sequestered so far from human populations may eventually prove worth the extra cost.