Basalt, a new weapon against global warming

NEW study suggests that the conventional wisdom – that it takes several hundreds to thousands of years to immobilise carbon dioxide as carbonate minerals within geologic reservoirs – may be fundamentally incorrect, opening a new, short-cycle pathway for carbon capture and storage.
Basalt, a new weapon against global warming Basalt, a new weapon against global warming Basalt, a new weapon against global warming Basalt, a new weapon against global warming Basalt, a new weapon against global warming

This could be good news for Papua New Guinea and its Pacific island neighbours which are directly in line to suffer the effects of rising seas caused by carbon emissions.

The study, published last week in the journal Science claimed to demonstrate for the first time the permanent disposal of carbon dioxide as environmentally benign carbonate minerals in basaltic rocks in as little as 24 months

A team of researchers from Columbia University, University of Iceland, University of Toulouse and Reykjavik Energy, led by lead author Dr Juerg Matter, found that over 95% of the carbon dioxide injected into the CarbFix site in Iceland was mineralised to carbonate minerals in less than two years.

Dr Matter said the CarbFix experience was "amazingly fast."

The gas was injected into a deep well at the study site in Iceland, which is made up of 90% basalt.

The carbon dioxide was dissolved in water and carried down the well. On contact with the target storage rocks, at 400-800 metres under the ground, the solution quickly reacted with the surrounding basaltic rock, which is rich in elements such as calcium, magnesium and iron, forming carbonate minerals.

The studies suggested the fast conversion rate of dissolved carbon dioxide to calcite minerals in the CarbFix storage reservoir is most likely due to the novel carbon dioxide injection system that injected water-dissolved carbon dioxide into the subsurface, the relatively rapid dissolution rate of basalt, the mixing of injected water with alkaline formation waters and the dissolution of pre-existing secondary carbonates at the onset of the carbon dioxide injection, which may have contributed to the neutralization of the injected carbon dioxide-rich water.

The researchers are optimistic that they can find similar areas and repeat the experiment on a larger scale.

"Basalt is one of the most common rock types on Earth, potentially providing one of the largest carbon dioxide storage capacities," Matter said.

It could be a viable way to remove anthropogenic emissions from the atmosphere, and lock them away.

Geoengineers have long explored the possibility of sealing carbon dioxide gas in voids underground, such as in abandoned oil and gas reservoirs, but these are susceptible to leakage, and researchers have been looking for other options.

Leakage rates into the atmosphere of less than 0.1% are required to ensure effective climate change mitigation.

"Carbonate minerals do not leak out of the ground, thus our newly developed method results in permanent and environmentally friendly storage of carbon dioxide emissions," Dr Matter said.

Tracers were used to assess the pathway of the carbon dioxide in eight monitoring wells.

The researchers discovered that by the time the groundwater had migrated to the monitoring wells, the concentration of the tracers - and therefore the carbon dioxide - had diminished, indicating that mineralisation had occurred.

Dr Matter said storing carbon dioxide has carbonate minerals could improve public acceptance of CCS.

"The overall scale of our study was relatively small. So, the obvious next step for CarbFix is to upscale carbon dioxide storage in basalt. This is currently happening at Reykjavik Energy's Hellisheidi geothermal power plant, where up to 5000 tonnes of carbon dioxide per year are captured and stored in a basaltic reservoir," he said.

CCS is considered a key way that industrial societies can continue to use fossil fuels, however trial projects to date have found it is costly and often inefficient to capture carbon dioxide.


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