Iceland Is Turning Carbon Emissions Into Stone

A test project locked a power plant’s carbon emissions underground in just two years, but it may not be workable in most parts of the world.
Carbon dioxide and hydrogen sulfide gas are captured in a separator, dissolved in water, and piped into this injection shed, a half mile from the power plant. (Photo: Kevin Krajick)
Jun 9, 2016· 2 MIN READ
Katharine Gammon has written for Nature, Wired, Discover, and Popular Science. A new mom, she lives in Santa Monica.

Four years ago, a power company in Iceland set out on an ambitious project to stick carbon emissions into the island nation’s basalt bedrock and keep them there.

On Thursday, the company announced that it has succeeded, reporting that 95 percent of the carbon stored underground at the Hellisheiði power plant, near Reykjavík, has mineralized less than two years after being injected into the earth.

“This is a really significant result,” said Roger Aines, a geochemist at Lawrence Livermore National Laboratory, who was not involved in the study. “It’s a way of storing carbon dioxide underground that prior to this research was thought to be too slow to be useful.”

When researchers and policy makers talk about carbon capture, they’re usually referring to injecting pure carbon dioxide into the earth’s crust or deep in the ocean. The problem is that the gas can seep out.

“The conventional wisdom is that it would take hundreds or thousands of years for the carbon to react with these rocks,” said Martin Stute, a hydrologist at Columbia University in New York and coauthor of the new study, published Thursday in the journal Science. But there was evidence that under the right conditions, carbon dioxide stored underground could become calcium carbonate—limestone—eliminating the risk of leaking or seeping.

In the 2012–13 pilot project, Stute and his colleagues mixed 250 tons of carbon dioxide and hydrogen sulfide—that gas that smells like rotten eggs—with water pumped from deep underground and injected the mixture 1,300 to 2,600 feet into the basalt. Preliminary testing in 2014 suggested almost all the carbon mineralized in less than two years. The newly published findings confirm that result.

“There was some studies showing the reaction could take place in a decade, but no one really believed this,” Stute said. “Yet in our study, it was only two years.”

The technology has requirements that may limit how widely it can be used. The pilot project was water intensive, taking about 10 gallons of water to convert and store one pound of carbon dioxide. Also, the technology requires basalt rock formations, which make up only about 10 percent of continental rocks.

But most of the ocean floor is basalt, and Stute said that it’s possible the technology could work using seawater. It is also possible that water used could be recycled, he said, because the reaction happens so quickly. “You don’t have to use freshwater all the time—it could be a loop,” he said. “You could dissolve carbon dioxide and pump it down in the well, precipitate the carbon minerals, and the water downstream has no more carbon dioxide in it.”

Cost could be an issue in scaling up the technology. In the pilot program, it cost about $30 per ton to store the carbon because the emissions from the geothermal plant were created close to the area where they were stored. But moving the carbon around is expensive, Stute said, and that cost could rise if the emissions need to be injected into rock more distant from their source.

Still, the technology is another tool for putting emissions underground and battling global climate change, said Aines. Experimental programs have placed 11 million tons of carbon dioxide underground safely so far, he said, mostly in old oil wells.