The innovative approach leverages heat to transform common minerals into highly reactive materials that naturally extract and store CO2. These materials can be produced using conventional kilns, similar to those used in cement manufacturing.
"The Earth holds vast mineral reserves capable of capturing atmospheric CO2, but their natural reactivity is too slow to counteract human emissions," said Matthew Kanan, a professor of chemistry at Stanford University and senior author of the Jan. 19 study published in Nature. "Our work offers a scalable solution to this problem."
Kanan and postdoctoral scholar Yuxuan Chen have developed a new method to convert slow-reacting silicates into more efficient CO2-absorbing materials. A grant from Stanford's Sustainability Accelerator is now helping transition this research toward real-world applications.
"We devised a novel chemistry to activate inert silicate minerals using a straightforward ion-exchange reaction," said Chen, the study's lead author. "We were surprised by how effectively it works."
Experts agree that curbing climate change requires both reducing fossil fuel use and removing billions of tons of CO2 from the atmosphere. However, many carbon capture technologies are costly, energy-intensive, or not yet viable at scale. Direct air capture (DAC), for instance, relies on large fans to funnel air through chemical filters to extract CO2.
"Our process requires less than half the energy of leading DAC technologies and is highly competitive in terms of cost," said Kanan, who is also a senior fellow at Stanford's Precourt Institute for Energy.
The Stanford researchers adapted this process by replacing sand with a magnesium silicate mineral. When heated, these materials undergo an ion exchange, generating magnesium oxide and calcium silicate-both highly reactive with CO2.
"The process effectively doubles the reactivity," Kanan explained. "We start with one reactive mineral and an inert magnesium silicate, and the reaction yields two minerals that efficiently capture CO2."
When exposed to water and pure CO2 at room temperature, the newly formed minerals quickly converted into carbonate minerals within two hours, permanently storing the carbon. A more realistic test, where the minerals were exposed to open air, showed significant CO2 capture within weeks to months-thousands of times faster than natural weathering.
This technique could also benefit farmers. Many agricultural operations add calcium carbonate to soil to regulate pH, a process known as liming. "Our method could eliminate the need for liming since both minerals are alkaline," Kanan noted. "Additionally, the release of silicon from calcium silicate into the soil could enhance crop yields and plant resilience. Ideally, farmers would pay for these minerals to improve soil productivity, while simultaneously removing carbon from the atmosphere."
Fortunately, the materials needed-magnesium silicates such as olivine and serpentine-are abundant worldwide. These minerals are also commonly found in mine tailings, offering a sustainable feedstock for carbon removal efforts. "Over 400 million tons of suitable mine tailings are generated annually, representing a vast potential resource," Chen noted. "With more than 100,000 gigatons of olivine and serpentine on Earth, the capacity for CO2 removal far exceeds historical emissions."
Even after accounting for the energy needed to power kilns, the team estimates each ton of reactive material produced could remove one ton of CO2 from the atmosphere. Given that global fossil fuel emissions surpassed 37 billion tons in 2024, the scalability of this technology is crucial.
To further enhance sustainability, Kanan is collaborating with Jonathan Fan, an associate professor of electrical engineering, to develop kilns powered by electricity instead of fossil fuels.
"The world already manufactures billions of tons of cement annually using kilns that operate for decades," Kanan said. "By leveraging existing industrial designs, we see a clear path from laboratory research to large-scale carbon removal."
Matthew Kanan is the director of Stanford's TomKat Center for Sustainable Energy. Yuxuan Chen is a postdoctoral scholar in materials science and engineering in Stanford's School of Engineering.
Research Report:Thermal Ca2+/Mg2+ exchange reactions to synthesize CO2 removal materials
Related Links
TomKat Center for Sustainable Energy
Carbon Worlds - where graphite, diamond, amorphous, fullerenes meet
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