Crushing rocks could capture CO2 equivalent to the size of Germany

Previous research explored trapping carbon into single minerals by the same method. Still, the study found that this carbon was unstable and dissolved from the mineral when placed in water.

According to the study, if the technology were used everywhere, it could take in 0.5 percent of the world's CO₂emissions, or 175 million tons of carbon dioxide per year. But Norway was used as an example for the calculation because the country publishes yearly data on how much hard rock aggregate is made for their construction industry.

Other countries, such as Australia and South Africa, will produce far more, as they have large mining industries and will look to crush and sell the waste rock, while others may make less.

The research team hopes that the sector could cut down on emissions by making changes to the way things are set up so that carbon from polluting gas streams, like those from making cement or gas-fired power plants, can be trapped. The technology could reduce the CO₂ footprint associated with building houses and public infrastructure, such as roads, bridges, and coastal defenses.

This new research could help industries reduce their carbon footprint in places without low-carbon solutions. It could also help many countries meet their commitments to the Paris Climate Accord.

The research team acknowledges that more work is needed to optimize the process and push the limits of how much carbon can be trapped through the crushing technique. They must also understand how this process can be scaled up from the lab to industry, where it can reduce global CO₂emissions.

"There are many industries for which there is currently no low-carbon solution. This research will allow direct gas capture of CO₂ [...] to decarbonize industries where a solution will not exist by 2050," said Principal investigator Professor Rebecca Lunn from the Department of Civil & Environmental Engineering.

"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."

"This breakthrough research from the University of Strathclyde [...] is truly revelatory. It points to a new process for the construction industry that could significantly reduce global carbon emissions and help us meet our net zero goals," said Dr. Lucy Martin, EPSRC's Deputy Director for Cross Council Programmes.

You can read the study for yourself in the journal Nature Sustainability.

Study abstract:

"Milling minerals rich in magnesium and iron within CO2 gas has been proposed to capture carbon as metal-carbonates. We conduct milling experiments in CO2 and show that polymineralic rocks such as granite and basalt, whether high or low in carbonate-forming metals, are more efficient at trapping CO2 than individual minerals. This is because the trapping process is not, as previously thought, based on the carbonation of carbonate-forming metals. Instead, CO2 is chemically adsorbed into the crystal structure, predominantly at the boundaries between different minerals. Leaching experiments on the milled mineral/rock powders show that CO2 trapped in single minerals is mainly soluble, whereas CO2 trapped in polymineralic rocks is not. Under ambient temperature conditions, polymineralic rocks can capture >13.4 mgCO2 g−1 as thermally stable, insoluble CO2. Polymineralic rocks are crushed worldwide to produce construction aggregate. If crushing processes could be conducted within a stream of effluent CO2 gas (as produced from cement manufacture), our findings suggest that for every 100 Mt of hard rock aggregate sold, 0.4–0.5 MtCO2 could be captured as a by-product."