Researchers claim CO2-absorbing rock could trap Gulf's emissions

US scientists have identified a technique that could trap up to four billion tonnes of carbon emissions a year underground by harnessing a natural reaction between carbon dioxide and the rock peridotite that converts the gas into minerals such as calcite.

Geologists have known for some time that peridotite – a naturally occurring rock that makes up most of the Earth's mantle and has been forced to the surface by tectonic activity in Oman, Papua New Guinea, Caledonia, and some areas of the Adriatic and California – reacts rapidly with carbon dioxide to form a solid carbonate like limestone or marble.

However, geologist Peter Kelemen and geochemist Juerg Matter of Columbia University's Lamont-Doherty Earth Observatory in New York claim to have discovered previously unknown high rates of reaction underground, which suggest that captured CO2 could be pumped underground and effectively soaked up by the peridotite.

According to the researchers, whose findings are due to be published in tomorrow's edition of the Proceedings of the Natural Academy of Sciences, the process of locking carbon dioxide into the rocks could be speded up to 100,000 times the naturally occurring rate simply by boring down and injecting heated water containing pressurised CO2.

Keleman said that the technique "would afford a low-cost, safe and permanent method to capture and store atmospheric CO2".

According to the researchers, peridotite deposits in Oman alone could absorb up to four billion tonnes of carbon dioxide a year – a substantial proportion of the 30 billion tonnes of man-made emissions pumped into the atmosphere annually.

"It's fortunate that we have these kinds of rocks in the Gulf region," said Matter, adding that they are conveniently close to the region's carbon-intensiv e oil and gas industries.

The researchers said that Oman's state oil company, Petroleum Development Oman, had expressed an interest in developing a pilot project to test the technique, which promises to be more cost-effective than mining peridotite and shipping it to power stations or oil refineries.

The project would represent the latest in a line of initiatives attempting to identify a means of trapping carbon emissions through chemical reactions with rocks, which advocates claim would present a lower risk of carbon leakage than plans to sequester carbon dioxide in semi-permeable rocks.

Matter has been working on a separate project in Iceland to test whether volcanic basalt could also be used to absorb CO2, while UK startup Carbon 8 is investigating using calcium silicates that result from industrial processes to react with CO2 to form limestone.