Transforming Everyday Rocks: The Innovative Technique That Turns Them into Carbon-Capturing Solutions

Carbon dioxide (CO2) is the leading greenhouse gas that humans release into our atmosphere. To tackle climate change, experts recommend reducing fossil fuel use and actively pulling CO2 out of the air. But existing carbon capture technologies can be costly and require a lot of energy, which makes them less practical for widespread use.

Researchers at Stanford University have come up with an innovative solution: using rocks to help capture CO2. Chemists Matthew Kanan and Yuxuan Chen have found a way to heat certain minerals, turning them into effective CO2 absorbers that can do this permanently. In their recent study published in the journal Nature, they describe a process that is both cost-effective and practical.

“The Earth has plenty of minerals that can absorb CO2, but they typically don’t react fast enough to offset our greenhouse gas emissions,” says Kanan. Their research aims to solve this issue using a scalable approach.

For many years, scientists have looked for ways to speed up the natural process by which rocks absorb CO2—a process known as weathering—which can take centuries. Kanan and Chen discovered a method to transform slow-reacting minerals, called silicates, into faster-reacting ones.

Their idea came from the world of cement production. During cement making, limestone is heated in a kiln to produce calcium oxide, which is then mixed with sand. The Stanford team adapted this process, using magnesium silicate instead of sand. The heating caused chemical exchanges that transformed the minerals into calcium silicate and magnesium oxide, both of which can absorb CO2 more quickly.

To test their method, they exposed a mix of wet calcium silicate and magnesium oxide to air. Within weeks or months, these materials turned into carbonate minerals, demonstrating effective weathering.

“Imagine spreading magnesium oxide and calcium silicate across large areas to capture CO2 from the air,” Kanan suggests. One exciting option they are exploring is adding these minerals to agricultural soil. This could help farmers who often add calcium carbonate to neutralize acidic soil, a process called liming.

“Our materials would eliminate the need for liming since both minerals are alkaline,” Kanan explains. “As calcium silicate weathers, it releases silicon that plants can absorb, which helps boost crop yields and resilience.” This dual benefit means farmers might be willing to invest in these minerals, not just for carbon removal but for healthier crops too.

Interestingly, around one ton of magnesium oxide and calcium silicate can absorb about one ton of CO2, even considering the emissions from the kilns used to create these minerals. Remarkably, this process uses less than half the energy of other carbon capture technologies.

However, to make a real impact, millions of tons of these minerals would need to be produced every year. Thankfully, if the natural reserves of magnesium silicates like olivine and serpentine are as abundant as estimated, they could potentially absorb all the CO2 emitted by humans and more. Additionally, these silicates can be sourced from mining leftovers.

“We already know how to produce billions of tons of cement each year, and those kilns operate for decades,” Kanan adds. “By leveraging this existing infrastructure and knowledge, we can transition from lab discoveries to large-scale carbon removal.”