Scientists turn CO2 into stone

Scientists and engineers at a major power plant in Iceland have turned carbon emissions into stone in just a matter of months. Their technique could provide a more secure alternative to storing CO2 emissions underground as gas.

The Hellisheidi power plant in Iceland is the world’s largest geothermal facility. While geothermal is generally regarded as a renewable source of energy, the process of extracting volcanically heated water also brings up volcanic gases, including carbon dioxide and hydrogen sulphide.

In 2012, scientists and engineers at the plant began mixing the gases with the water pumped from below and re-injecting the solution into the volcanic basalt below. The results were surprising even to them: 95 per cent of the injected carbon was solidified within less than two years, according to a statement from the Earth Institute at Columbia University, which participated in the pilot project called Carbfix.

“This means that we can pump down large amounts of CO2 and store it in a very safe way over a very short period of time,” said Martin Stute, a hydrologist at Columbia University and co-author of the study, which was recently published in the journal Science. “In the future, we could think of using this for power plants in places where there’s a lot of basalt – and there are many such places.”

The researchers regard this as a very promising alternative to carbon capture and sequestration in its gas form, which is considered less secure because the emissions could make their way back up to the surface through fractures or earthquakes. The new technique is also very fast, which could keep costs down. In the 2012 and 2013 pilot, much of the carbon had mineralised within months.

Lead author Juerg Matter, who is now based at the University of Southampton, said: “We need to deal with rising carbon emissions. This is the ultimate permanent storage—turn them back to stone.”


Image credit: UN Photo/Eskinder Debebe

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