An international team of scientists has developed a method for the permanent and environmentally friendly storage of carbon dioxide (CO2) emissions caused by humans by turning it into rocks.
The study, published in the journal Science, has showed that the greenhouse gas CO2 can be permanently and rapidly locked away from the atmosphere, by injecting it into volcanic bedrock.
The CO2 reacts with the surrounding rock, forming environmentally benign minerals.
"Our newly developed method results in permanent and environmentally friendly storage of CO2 emissions," said the study's lead author Juerg Matter, associate professor in Geoengineering at University of Southampton in Britain.
Measures to tackle the problem of increasing greenhouse gas emissions and resultant climate change are numerous. One approach is Carbon Capture and Storage (CCS), where CO2 is physically removed from the atmosphere and trapped underground.
Geoengineers have long explored the possibility of sealing CO2 gas in voids underground, such as in abandoned oil and gas reservoirs, but these are susceptible to leakage. So attention has now turned to the mineralisation of carbon to permanently dispose of CO2.
Until now it was thought that this process would take several hundreds to thousands of years and is therefore not a practical option.
But the current study has demonstrated that it can take as little as 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," Matter pointed out.
The gas was injected into a deep well at the study site in Iceland. As a volcanic island, Iceland is made up of 90 per cent basalt, a rock rich in elements such as calcium, magnesium and iron that are required for carbon mineralisation.
The CO2 is 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 reacts with the surrounding basaltic rock, forming 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," Matter said.
"On the other hand, basalt is one of the most common rock type on Earth, potentially providing one of the largest CO2 storage capacity," he noted.
The study is part of the CarbFix project, a European Commission and US Department of Energy funded programme to develop ways to store anthropogenic CO2 in basaltic rocks through field, laboratory and modelling studies.
