In Iceland, engineers have cracked a way to turn CO2 into stone

10 Jun 2016

An experimental drill core held by coauthor Sandra Snaebjornsdottir. Image via Kevin Krajick/Lamont-Doherty Earth Observatory

Researchers and engineers in Iceland are embarking on a new age of carbon capture after they revealed an astounding ability to turn captured CO2 emissions into harmless stone.

While efforts are being made globally to cut down on CO2 emissions through greater adoption of renewable energy, it’s still the reality that many nations are continuing to emit enormous quantities of the gas into the upper reaches of our atmosphere.

That’s why, in an effort to reduce the amount of harmful gases in the air, considerable efforts have been made to extract CO2 from the atmosphere and pump it into relative safety underground.

Future Human

Relative being the key term here as, while it might make the atmosphere a little cleaner, storing these emissions underground often sees them seep out to the surface or, more worryingly, explode rather violently.

Now, however, a team of engineers and researchers in Iceland have managed to find a way of turning this gas into solid stone much faster than previous attempts – in only a matter of months – with the results published in the journal Science.

Work on this carbon-to-stone technology began back in 2012 under the Carbfix pilot project, which mixed the gas with water and reinjected it into the volcanic basalt that’s abundant beneath Iceland.

Rock sample

A closer look at the rock sample. Image via Annette K. Mortensen

‘A very welcome surprise’

While it was known this process eventually turns the CO2 into chalky material, it was believed that it would take hundreds, if not thousands, of years to solidify to become rock.

And yet, the University of Columbia team has revealed that, astonishingly, after just two years, 95pc of the 250 tonnes of injected carbon had solidified.

This was despite the head of the project for Reykjavik Energy, Edda Aradottir, having previously estimated that the best case scenario would take between eight and 12 years, and he has called this discovery “a very welcome surprise”.

The new CO2-derived rock originated from emissions of the neighbouring geothermal power plant of Hellisheidi, which, despite being a renewable energy, also brings up volcanic gases, including CO2 and hydrogen sulphide.

Iceland plant

Air photograph of Reykjavik Energy’s Hellisheidi geothermal power plant. Image via Árni Sæberg

So, why was it so successful?

Compared with previous attempts at carbon capture, the surrounding basalt contained plenty of calcium, iron and magnesium, and water was also pumped down with the CO2, which had not been done before.

Co-author of the study, Sigurdur Gislason of the University of Iceland, said he believes this breakthrough will be best used by large fossil-fuel power plants, smelters and heavy industry.

The only stumbling blocks to any adoption, however, is that it will need to be pumped into basalt rock, in addition to 25 tonnes of water being required.

‘This is the ultimate permanent storage’

Another potential issue comes from nature itself, with a recent study revealing the existence of subterranean microbes that seem to feed off such carbonate minerals and subsequently turning it into the even more damaging gas, methane.

Having once thought to only exist deep on the planet’s ocean floors, it is now becoming apparent that they are more widespread, having been discovered in a spring in California.

Regardless of the challenges, the researchers believe this offers the best solution yet for some of the biggest polluters to help combat their damage to the environment in the years to come.

“We need to deal with rising carbon emissions,” said lead author Juerg Matter. “This is the ultimate permanent storage – turn them back to stone.”

Colm Gorey was a senior journalist with Silicon Republic