Arni Saeberg

Researchers turn CO2 into stone

Posted on 28 October 2016.

International researchers have developed a safe and effective method for capturing and storing CO2 underground - they turn it into "stone".

Unlike conventional methods which store CO2 in gas form, the new CarbFix method stores it in the solid state.

Capturing and storing carbon dioxide (the CCS sector) from power plants and factories before it enters the atmosphere could help mitigate global warming. According to the Intergovernmental Panel on Climate Change (IPCC), it could even be essential in meeting the targets for reducing greenhouse gas (GHG) emissions. The problem is that although several techniques have already been perfected, their development is limited due to their cost and the risks associated with CCS: the gas may escape into the atmosphere or into aquifers.

But an international team may have found the solution. Called "CarbFix" (Creating the technology for safe, long-term carbon storage in the subsurface), the method developed by the University of Iceland, the CNRS, the Earth Institute at Columbia University and the company Reykjavik Energy has been tested for several years on the Hellisheidi geothermal power plant site - the largest in Iceland.

Solidifying the gas

A renewable energy, geothermal energy is not completely carbon-free since exploiting the Earth’s heat brings up volcanic gases such as CO2 and hydrogen sulfide. The CarbFix project consists of capturing these gases, dissolving them in water and then injecting them into the basalt more than 400 m down. A chemical reaction then takes place which converts the carbon dioxide into a solid carbonate mineral- a sort of stone. Unlike conventional CCS methods, which inject CO2 into the earth's crust in the form of gas, the CarbFix method stores it in the solid state.

The experiment conducted in Hellisheidi has shown that it is possible to trap large amounts of CO2 in the Earth’s crust, "solidify" the gas in a very short period of time, thus storing it safely (much less risk of leakage) and almost permanently. 95% of the CO2 captured and injected into the volcanic rock was mineralized in the space of two years (scientists had predicted hundreds of years and even millennia!). A major advance. According to project officials, the CarbFix method could be used in coal plants, which emit far more carbon dioxide, if they are located in places where there is a lot of basalt - a widely available resource on the planet.

Sandra O. Snaebjornsdottir
Sandra O. Snaebjornsdottir