Stanford chemists turned ordinary rocks into carbon-trapping materials that work thousands of times faster than nature by borrowing a trick from centuries-old cement-making and the results could reshape how humanity fights climate change

Pulling billions of tons of CO2 out of the atmosphere is one of the hardest things humanity has ever attempted. The technologies built for it — giant fan systems, experimental ocean interventions — are expensive, energy-intensive, and still nowhere near the scale the climate needs.

Now Stanford chemists say the answer may have been sitting underfoot the whole time: common rocks, a kiln, and a chemical trick borrowed from centuries of cement-making.

A centuries-old technique, repurposed for the climate crisis

The inspiration came from cement-making — one of humanity’s oldest industrial processes. Traditional cement production starts by heating limestone in a kiln to roughly 1,400 degrees Celsius, converting it into calcium oxide. That calcium oxide then mixes with sand to produce a key binding ingredient.

Heated together, the two materials exchanged ions — calcium and magnesium trading places — producing two new minerals: magnesium oxide and calcium silicate.

Stanford chemist Matthew Kanan and postdoctoral scholar Yuxuan Chen followed a similar path, but swapped the sand for a magnesium silicate mineral. Heated together, the two materials exchanged ions — calcium and magnesium trading places — producing two new minerals: magnesium oxide and calcium silicate.

Both are alkaline and react readily with acidic CO2 in the air, and both can be made in conventional kiln designs already proven at industrial scale. “The process acts as a multiplier,” Kanan said. “You take one reactive mineral, calcium oxide, and a magnesium silicate that is more or less inert, and you generate two reactive minerals.”

How fast does it actually work?

Speed is where the chemistry gets interesting. In lab tests using pure CO2, both magnesium oxide and calcium silicate fully carbonated within two hours at room temperature — carbon locked inside stable mineral structures faster than it takes to watch a movie.

Real-world air is a harder test. Atmospheric CO2 concentrations are far lower than a pure tank of gas, so when wet samples were exposed to ordinary air, carbonation took weeks to months. That sounds slow — until you consider the alternative. Natural silicate weathering takes hundreds to thousands of years. Even at its slowest, the Stanford process is thousands of times faster, with carbon ending up permanently trapped inside stable carbonate minerals or as bicarbonate ions.

Energy and cost advantages over direct air capture

Direct air capture has attracted real attention and early investment. The idea is straightforward: large fans push ambient air through chemical processes that strip out CO2. The problem is energy. These systems are intensely power-hungry, which drives up both cost and carbon footprint.

The Stanford process, Kanan says, would require less than half the energy of leading direct air capture technologies. That gap matters enormously when you’re trying to remove carbon at billions of tons per year — lower energy demand means lower operating costs and a smaller emissions penalty from the process itself. After accounting for CO2 released by burning fuel to run the kilns, the researchers estimate each ton of reactive material produced can remove approximately one ton of CO2 from the atmosphere.

From lab benches to farm fields — and the ocean floor

One of the most promising near-term applications isn’t an industrial facility. It’s a farm. Kanan’s team is actively testing whether spreading these minerals over agricultural land could serve as a practical, large-scale deployment pathway.

As magnesium oxide and calcium silicate weather in soil, they release bicarbonate ions that migrate through groundwater and eventually reach the ocean, where they’re stored permanently. The process mirrors natural rock weathering — just at a pace useful on human timescales. Farmers routinely add calcium carbonate to acidic soils to raise pH, a practice called liming, and both new minerals are alkaline enough to replace that input entirely. Calcium silicate also releases silicon in a form plants can absorb, which research suggests may improve crop yields and resilience — an economic incentive that doesn’t depend on carbon markets at all.

Raw materials are abundant — the challenge is scaling up

The feedstocks are neither rare nor exotic. Olivine and serpentine — magnesium silicate minerals — are found worldwide and are a common byproduct of mining operations. Chen estimates that more than 400 million tons of suitable mine tailings are generated globally each year. Estimated global supplies of olivine and serpentine exceed 100,000 gigatons — enough, in principle, to permanently remove more CO2 than humans have ever emitted throughout history.

The bottleneck isn’t raw material. It’s production. Kanan’s lab currently produces around 15 kilograms per week, while meaningful climate impact would require millions of tons annually. Kanan is already collaborating with Stanford electrical engineering professor Jonathan Fan to develop kilns powered by electricity rather than fossil fuels, which would cut the process’s emissions footprint further.

The path from 15 kilograms a week to industrial scale is long. But the blueprint already exists in cement plants that have run continuously for decades, producing billions of tons of material per year. If those designs can be adapted, the researchers believe a clear route from laboratory discovery to global-scale carbon removal is within reach.

If you want to discover more about these findings, you can check the complete study here: Yuxuan Chen, Matthew W. Kanan. Thermal Ca2+/Mg2 exchange reactions to synthesize CO2 removal materials. Nature, 2025; DOI: 10.1038/s41586-024-08499-2

Daniel Garcia

Daniel García is an Editor-in-Chief with strong expertise in structural work and engineering principles. He combines this technical foundation with deep knowledge of energy, spatial design, and emerging technologies, bringing a forward-thinking and analytical approach to editorial leadership.