climate change science

Turning waste CO2 into stone

Iceland, as you may be aware, is one of the select few countries with 100% renewable energy. But this week it announced that it’s gone one better – scientists have managed to turn CO2 into stone.

CO2 dissolved in water is pumped into the ground to a depth of 54o metres. There minerals in the basaltic rock react with the CO2 and turn it into limestone. This can be observed in the natural volcanic environment in Iceland, so the project has been attempting to replicate and accelerate something that occurs naturally. It’s taken them nine years to do it, but yesterday they were able to announce that field tests have been successful. Not only did the pumped-in CO2 turn to solids, it did so in under two years – much faster than expected.

This throws a lifeline to the idea of carbon capture and storage (CCS), which has so far failed to catch on at any significant scale. One of the big problems with CCS is that there are limited places where CO2 can be stored. It can be pumped into saline aquifers or depleted gas fields, but options are limited. A second problem is keeping the CO2 there, and preventing it leaking back out and making the whole process rather futile.

basaltStoring CO2 in rock solves both of those problems. Once it has been converted into limestone, the CO2 is gone. It’s not a gas any more, so it can’t leak out. It should be stable for many thousands of years. And basaltic rock is common. Iceland has the biggest expanse of it above water, but it is found in many other coastal areas and it is abundant on the sea floor.

So far the process is experimental and isn’t commercially viable yet, but the advantages over other forms of CO2 storage give it an edge that might attract some interest from funders where other technologies have failed.

As always, CCS is not vital to addressing climate change, but neither does it deserve the snap dismissal that some environmental organisations give it. Some are sceptical about it because it would theoretically allow us to continue using fossil fuels, and would thus delay the transition to clean energy. But the economics of fossil fuels are changing anyway, and coal with CCS can’t compete with renewable energy on price. Where CCS will come in most useful is not in electricity generation, but in industries such as steel or cement. We’re going to need those for the foreseeable future, particularly in emerging economies. There’s an infrastructure boom that inevitably comes with development. If CCS in rock can be scaled up, lower income countries may be able to leapfrog to cleaner CCS-fitted heavy industry as they hit the building frenzy, and that would be better for the atmosphere and thus for all of us.

For more information, look up the CarbFix Project.

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