New process could capture 0.5 per cent of global CO2 emissions

The team at Strathclyde University published its research in Nature Sustainability, outlining how CO2 emissions can be captured during the normal crushing process of rocks commonly used in construction, by crushing them in CO2 gas. According to the team, almost no additional energy would be required to trap the CO2.

The materials and construction industry accounts for 11 per cent of global carbon emissions. More than 50 billion tonnes of rock is crushed worldwide every year and current crushing processes – standard in construction and mining – do not capture CO2.

Previous work has explored trapping carbon into single minerals by the same method, but the Strathclyde team’s research shows this is unstable and dissolves out of the mineral when placed in water. 

The paper documents how a larger proportion of carbon dioxide can be trapped in a stable, insoluble form in rocks composed of multiple different minerals by grinding it in CO2 gas. The resulting rock powders can then be stored and used in the environment for construction and other purposes.

Researchers said that the calculation of 0.5 per cent was made for Norway, as an example, because the country publishes annual data on the volume of hard rock aggregate produced for their construction industry, and their annual national CO2 emissions are also documented.

Principal investigator Professor Rebecca Lunn, from the Department of Civil & Environmental Engineering, said: “The hope is that the sector could reduce the emissions by adapting the current setups to trap carbon from polluting gas streams such as those from cement manufacture or gas-fired power stations.

“The global estimate is based on the assumption that Norway’s construction industry is reasonably typical. Some countries such as Australia and South Africa will actually produce far more, as they have large mining industries and will look to crush and sell the waste rock, while others may be less.”

Professor Lunn said that if the technology was adopted worldwide in aggregate production, it could potentially capture 175 million tonnes of CO2 annually – future research could pin this down and optimise the process to trap more carbon, she added.

Co-investigator Dr Mark Stillings commented: “Now we know that CO2 trapping in most hard rock can be done in a lab, we need to optimise the process and push the limits of how much can be trapped through the crushing technique. We then need to understand how this process can be scaled up from the lab to industry, where it can reduce global CO2 emissions.”

Professor Lunn added that in future, the team hopes that the rock used in concrete to construct high rise buildings and other infrastructure such as roads, bridges and coastal defences will have undergone the process and trapped CO2 that would otherwise have been released into the atmosphere.

The work was funded by the Engineering and Physical Sciences Research Council’s (EPSRC) Doctoral Training Awards Grant.