Engineers set to convert carbon dioxide into rock

The project will take CO2 produced by an Icelandic geothermal energy plant and dissolve it in water under high pressures. It will then pump the solution into layers of basalt about 400-700m underground Photograph: Paul A Souders/Corbis

Engineers in Iceland are set to convert carbon dioxide to solid rock as a way to tackle global warming.

The experts want to exploit the country's volcanic origins to dispose of up to 30,000 tonnes of the greenhouse gas each year. They expect the gas to react with layers of volcanic rocks deep beneath the surface to form minerals that will lock the carbon pollution away for millions of years.

"This is a well-known natural process," said Holmfridur Sigurdardottir, project manager. "We are just trying to imitate what nature is doing."

The project will take CO2 produced by an Icelandic geothermal energy plant and dissolve it in water under high pressures. It will then pump the solution into layers of basalt about 400-700m underground, and watch what happens.

Laboratory experiments suggest the dissolved CO2 will react with calcium in the basalt to form solid calcium carbonate. Sigurdardottir said: "In the lab it takes a few days to a few weeks. We want to see what happens in the field and whether we can do it on the scale required."

The project, called Carb-fix, is a form of carbon capture and storage (CCS). Such schemes usually aim to pump the CO2 into deep saltwater reservoirs, where the high pressure is expected to keep the gas dissolved and trapped underground. Mineral storage offers a safer bet, Carb-fix says, because there is less chance of leakage.

Domenik Wolff-Boenisch from the University of Iceland, who works on the project, will tell the annual meeting of the European Geosciences Union in Vienna next week that "storage of carbon dioxide as solid carbonate in basaltic rocks may provide an ideal solution".

The project is scheduled to begin pumping down the dissolved CO2 in August, Sigurdardottir said. It will take about a year before the team knows whether the gas is converting to minerals as expected.

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