Stanford University chemists have developed a process that successfully converts slow-weathering silicates into much more reactive minerals that capture and store atmospheric CO2 more rapidly.
Senior research author, Professor Matthew Kanan, and Stanford postdoctoral fellow Yuxuan Chen developed and demonstrated the novel process at Kanan’s laboratory at Stanford University.
What the research team was able to create is a version of a carbon removal technology called enhanced rock weathering, through which the carbon-absorbing abilities of certain types of rocks are accelerated via different technological mechanisms.
The Kanan-Chen team was inspired by the kiln processes in cement production, where limestone is heated to about 1,400 degrees Celsius to be converted into calcium oxide that then gets mixed with sand to produce a key cement ingredient.
Following a similar process, the chemists combined calcium oxide with another mineral that contains magnesium and silicate ions. When put through heating, the two minerals transformed into magnesium oxide and calcium silicate—two alkaline minerals that have the ability to quickly react with acidic atmospheric carbon dioxide.
Lead research author Chen explained, “We envisioned a new chemistry to activate the inert silicate minerals through a simple ion-exchange reaction. We didn’t expect that it would work as well as it does.”
The scientists tested the reactivity of the new alkaline minerals at room temperature, exposing them to pure CO2 and water. It took two hours for both the calcium silicate and magnesium oxide to fully transform into new carbonate minerals that successfully trapped carbon dioxide in their structure.
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Wet samples of calcium silicate and magnesium oxide were also tested in a more realistic setup, where they were exposed directly to air that is not as rich in concentrated CO2 as a tank.
In this scenario, it took the materials weeks to months to carbonate, which might sound slow, but the team points out that it is still a faster option than natural weathering.
Backed by a grant from the Sustainability Accelerator at the Stanford Doerr School of Sustainability, this CO2 removal research will be evaluated for deployment in practical applications.
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