For years, scientists and others concerned about climate change have been talking about the need for carbon capture and sequestration.
That is the term for removing carbon dioxide from, say, a coal-burning power plant’s smokestack and pumping it deep underground to keep it out of the atmosphere, where it would otherwise contribute to global warming.
C.C.S., as the process is known, has had a spotty record so far. While there are some projects being designed or under construction, only one power plant, in Canada, currently captures and stores carbon on a commercial scale (and it has been having problems). Keeping a lot of CO2 out of the atmosphere would require a costly expansion of the technology to many more power plants and other industrial facilities.
Among the concerns about sequestration is that carbon dioxide in gaseous or liquid form that is pumped underground might escape back to the atmosphere. So storage sites would have to be monitored, potentially for decades or centuries.
But scientists at Lamont-Doherty Earth Observatory at Columbia University and other institutions have come up with a different way to store CO2 that might eliminate that problem. Their approach involves dissolving the gas with water and pumping the resulting mixture — soda water, essentially — down into certain kinds of rocks, where the CO2 reacts with the rock to form a mineral called calcite. By turning the gas into stone, scientists can lock it away permanently.
One key to the approach is to find the right kind of rocks. Volcanic rocks called basalts are excellent for this process, because they are rich in calcium, magnesium and iron, which react with CO2.
Iceland is practically all basalt, so for several years the researchers and an Icelandic utility have been testing the technology on the island. The project, called CarbFix, uses carbon dioxide that bubbles up naturally with the hot magma that powers a geothermal electrical generating plant 15 miles east of the capital, Reykjavik (Read more about it here).
In 2012, they pumped about 250 tons of carbon dioxide, mixed with water, about 1,500 feet down into porous basalt. The CO2 was laced with a radioactive isotope and there were other compounds in the water that helped the researchers trace its spread into the rock.
Early signs were encouraging: Among other things, a submerged pump that was used to obtain samples of the mixture as it spread underground stopped working after a while because it got gummed up by calcite. And now the scientists have reported more authoritative evidence that their technology works, in a paper published in the journal Science.
The scientists found that about 95 percent of the carbon dioxide was converted into calcite. And even more important, they wrote, the conversion happened relatively quickly — in less than two years.
“It’s beyond all our expectations,” said Edda Aradottir, who manages the project for the utility, Reykjavik Energy.
Rapid conversion of the CO2 means that a project would probably have to be monitored for a far shorter time than a more conventional sequestration site.