Chemistry expertise speeds up rocks’ ability to absorb CO2

The new process will allow crushed rocks to capture carbon dioxide more quickly from the air by turbocharged with already widely adopted carbon removal techniques.

Natural silicate minerals such as basalt react with water and CO2 to form solid carbonic acid materials, a process known as reinforced lock weathering (ERW). Research suggests Spreading crushed silicate rocks on farmland increases the amount of carbon the soil can absorb, while improving farmer crop yields.

but Matthew Canan Stanford University in California believes that the carbon advantage of ERW is exaggerated as natural silicates do not reach the climate quickly enough to extract large amounts of carbon from the atmosphere. “The data is very clear. They don’t weather at a useful speed,” he says.

Conversion of silicates into more reactive minerals increases weathering rates and makes ERW a viable climate solution, he says. Canaan and his colleagues Yuxuan Chen Stanford University also developed a method for producing magnesium oxide and calcium silicate using a process inspired by cement production.

“When you take calcium sources and magnesium silicate and heat it, you can make calcium silicate and magnesium oxide,” says Canaan. “The core reaction is what is called ion exchange, and it exchanges magnesium for calcium.”

“The reason it’s strong is because calcium silicate is reactive and so is magnesium oxide,” he says. “I put one reactive thing in and two come out.” The ingredients get the weather thousands of times faster than standard silicates, says Canaan.

The ki used in this process must be heated to 1400°C for the reaction, and energy may be provided by natural gas. This means that this method generates significant carbon emissions, but Canaan can capture these at sources or use several reactive minerals to capture the emissions at the site. It suggests that booking can offset it.

When the emissions associated with material production are taken into consideration, one ton of reactive material removes about one ton of carbon dioxide from the atmosphere. Researchers can now create 15 kilograms of reactive rocks per day, but they hope to turn the idea into a commercial venture by selling the materials to farmers for use on farmland.

Rachel James The University of Southampton, UK, challenges Canaan’s claim that traditional ERWs do not work, pointing to many documented examples of intensified weathering tests. However, she welcomes attempts to accelerate the weathering rate of silicate.

“The climate crisis now requires action, so what you can do to speed up weathering rates is extremely beneficial,” she says. “Weathering is essentially a slow process and frankly, we want to see meaningful carbon dioxide removal on a timescale of 10 years or more than 50 years.”

However, she warns that the team is likely to face problems with expanding production and deployment. She says that using minerals in agricultural systems does not guarantee that all captured carbon is permanently trapped.

Phil Renforth At Heriot Watt University in Edinburgh, UK, the proposal is said to be a smart idea, but it takes more research to understand how it should be unfolded. “They essentially produce cement minerals, which may not be an ideal candidate mineral in addition to agricultural soils,” he says.