Posted in | Climate Change

Scientists Turn Carbon Dioxide into Rock to Combat Climate Change

Researchers have discovered a potential way to eliminate anthropogenic carbon dioxide (CO2) emissions from the atmosphere by turning CO2 into a rock. Anthropogenic CO2 emissions are generally caused by humans.

Section of rock core from the CO2 storage reservoir showing vesicular basalt with a well-defined fracture with calcium carbonate mineralization. (Credit: Annette K. Mortensen.)

In a study published in the Science journal, researchers, for the first time, have revealed that by injecting the greenhouse gas CO2 into volcanic bedrock, the gas can be locked away quickly and permanently from the atmosphere. The confined CO2 then reacts with the nearby rock and forms eco-friendly minerals.

There are numerous ways to tackle the increasing problem of greenhouse gas emissions and climate change. The innovative Carbon Capture and Storage (CCS) solution is one method where CO2 is actually removed from the air and stored underground. For a long time, geoengineers have been studying the possibility of locking away CO2 gas in underground holes, such as in gas reservoirs and abandoned oil. However, these are vulnerable to leakage. Therefore, researchers have turned to carbon mineralization to remove the CO2 gas permanently.

Till now it was believed that this process would be very challenging and could take many years to complete, and hence is not a feasible choice. However, the new study, headed by Reykjavik Energy, University of Iceland, Columbia University and University of Toulouse, has revealed that this process can take just two years.

Our results show that between 95 and 98 per cent of the injected CO2 was mineralised over the period of less than two years, which is amazingly fast.

Lead author Dr Juerg Matter, Associate Professor in Geoengineering at the University of Southampton

The CO2 gas was infused into a deep well in Iceland, a volcanic island made of 90% basalt. Basalt is a rock rich in elements such as magnesium, iron, and calcium that are necessary for carbon mineralization. The CO2 gas is mixed in water and pumped down the well. When the solution reaches the target storage rocks at 400-800m below the ground, it rapidly reacts with the nearby basaltic rock and forms carbonate minerals.

"Carbonate minerals do not leak out of the ground, thus our newly developed method results in permanent and environmentally friendly storage of CO2 emissions," says Dr Matter, who is also a member of the University's Southampton Marine and Maritime Institute and Adjunct Senior Scientist at Lamont-Doherty Earth Observatory Columbia University. "On the other hand, basalt is one of the most common rock type on Earth, potentially providing one of the largest CO2 storage capacity."

In order to monitor the process underground, the researchers also injected chemical compounds called 'tracers' to track the transport path as well as the reactivity of the CO2 gas. The study site contained eight monitoring wells to test the transformation of the water’s chemical composition. During this process, the researchers identified that by the time the groundwater had transferred to the monitoring wells, the tracers’ concentration had reduced, pointing out that the carbon mineralization had indeed taken place.

Storing CO2 as carbonate minerals significantly enhances storage security which should improve public acceptance of Carbon Capture and Storage as a climate change mitigation technology.

Dr Matter.

"The overall scale of our study was relatively small. So, the obvious next step for CarbFix is to upscale CO2 storage in basalt. This is currently happening at Reykjavik Energy's Hellisheidi geothermal power plant, where up to 5,000 tonnes of CO2 per year are captured and stored in a basaltic reservoir."

This research is part of the CarbFix project, a programme funded by a European Commission and U.S. Department of Energy to develop new methods for storing anthropogenic CO2 in rocks through laboratory, modelling, and field studies.

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