The materials and construction industry accounts for 11% of global carbon emissions. More than 50 billion tonnes of rock are crushed worldwide every year. Current crushing processes – standard in construction and mining – do not capture CO2.
Now, new research at the University of Strathclyde, Glasgow, suggests that around 0.5% of global carbon emissions could be captured during the normal crushing process of rocks commonly used in construction by crushing them in CO2 gas. Researchers say this way, almost no additional energy would be required to trap the CO2. This 0.5% of global carbon emissions would be equivalent to planning a forest of mature trees the size of Germany.
Researchers previously explored trapping carbon into single minerals by the same method. But the new research shows this is unstable and dissolves out of the mineral when placed in water.
The paper describes 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.
“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,” said the principal investigator Professor Rebecca Lunn. “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.”
“If the technology was adopted worldwide in aggregate production, it could potentially capture 0.5% of global CO2 emissions – 175 million tonnes of carbon dioxide annually. Future research can pin this down, as well as optimize the process to trap more carbon.”
Co-investigator Dr. Mark Stillings added, “Now we know that CO2 trapping in most hard rock can be done in a lab, we need to optimize 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.”
“If this process was applied, the CO2 footprint associated with building houses and public infrastructure could be greatly reduced, helping to meet global objectives to combat climate change,” he continues.
There are many industries for which there is currently no low-carbon solution. Scientists believe that their research would allow direct gas capture of CO2 from hard-to-decarbonize industries, where a solution is not going to exist by 2050.
“In the future, we hope that the rock used in concrete to construct high-rise buildings and other infrastructure such as roads, bridges, and coastal defenses will have undergone this process and trapped CO2, which would otherwise have been released into the atmosphere and contributed to global temperature rise,” Professor Lunn added.
- Mark Stillings, Zoe K. Shipton, and Rebecca J. Lunn. Mechanochemical processing of silicate rocks to trap CO2. Nature Sustainability, 2023; DOI: 10.1038/s41893-023-01083-y