Spreading crushed rocks on fields can absorb CO2 from the air – now chemists have devised a way to turbocharge this process by creating more reactive minerals
By Madeleine Cuff
19 February 2025
Olivine rock naturally reacts with carbon dioxide, but it is a slow business
Renhour48 via Wikimedia/CC0 1.0 Universal
A new process could enable crushed rocks to capture carbon dioxide from the air much more quickly, turbocharging a carbon removal technique that is already being widely adopted.
Natural silicate minerals such as basalt react with water and CO2 to form solid carbonate materials, a process known as enhanced rock weathering (ERW). Studies suggest spreading crushed silicate rocks on agricultural land can increase the amount of carbon that soils can absorb, while also improving crop yields for farmers.
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But Matthew Kanan at Stanford University in California believes the carbon benefits of ERW have been overblown, because natural silicates don’t weather quickly enough to extract meaningful amounts of carbon from the air. “The data is very clear: they do not weather at useful rates,” he says.
Converting silicates into more reactive minerals would increase the weathering rate, making ERW a viable climate solution, he says. Kanan and his colleague Yuxuan Chen, also at Stanford University, have developed a way to produce magnesium oxide and calcium silicate using a process inspired by cement production.
“You can take a calcium source and a magnesium silicate, heat them up, and you end up making a calcium silicate and a magnesium oxide,” says Kanan. “The core reaction is what we call an ion exchange, where we are swapping magnesium for calcium.”