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Hellisheidi geothermal power plant
ThinkGeoEnergy on Flickr/CC BY 2.0
Hellisheidi geothermal power plant in Iceland was the site of an innovative study in converting carbon into rock.
ROCK SOLID

Iceland has developed an ingenious solution for combatting carbon emissions

By Kelsey Kennedy

Researchers in Iceland have developed a process to limit carbon dioxide from energy production escaping into the atmosphere, by converting the CO2 into solid rock. Such a process could create a permanent storage solution for some of the tons of CO2 pumped into the atmosphere each year.

The process involves injecting CO2 and water into the ground, where the mixture reacts with surrounding rock to form stone. The mineralization of the gas took about two years, which is a much shorter time period than researchers expected.

Until now, injecting CO2 into underground reservoirs hasn’t provided feasible storage for one big reason: leaks. Gas seeps out and escapes when seismic activity creates cracks in impermeable rock. To mitigate this issue, the team in Iceland blended CO2 with hydrogen sulfide and water, then injected it into porous basalt. The researchers hoped the mixture would react with the basalt and solidify into stone over about 10 years.

After checking on the mixture less than two years later, they were surprised to find about 95% of their injection had already formed carbonate rock. They described their findings in a report this week in the journal Science.

Researchers tried the process out at a hydrothermal power plant in Iceland because it allowed them to capture the gas directly from the turbines. The process holds potential for other power plants, but would require separating out oxygen and nitrogen from the CO2.

So far the technique has only been used to store CO2 in Iceland, but Martin Stute, one of the report’s coauthors and a hydrologist at the Columbia University Lamont-Doherty Earth Observatory, says there are more places where it could work.

This means finding basalt formations in countries other than Iceland. Basalt typically forms when lava cools, and makes up the edges of continental plates and about 90% of ocean floors. Water is another key component, and it doesn’t have to be high quality, Stute saysThe report points to North America’s Pacific Northwest coast as a prime area for this method of carbon sequestration, thanks to abundant basalt and water. ”If it works, that would be a pretty big chunk of the power plants in the world.”

Fossil fuel use releases over nine billion metric tons of CO2 annually, a 90% increase from 1970. This method has the potential to remove a “significant fraction” of that output, Stute says. Not all of those emissions come from power plants, and capturing and injecting CO2 from mobile sources of emissions, such as cars and other forms of transport, isn’t feasible.  ”It’s not solving the problem,” says Stute. “It’s part of the solution, not a silver bullet.”