Montreal—When it comes to combating climate change, reducing emissions is step one. But after eliminating CO2 sources, Earth’s carbon cycle will take centuries to remove enough of the greenhouse gas to begin lowering global temperatures. Scientists want to give those natural processes a boost.
On Monday at the 36th annual Goldschmidt conference on geochemistry, Stanford University’s Matt Kanan and other scientists gathered to discuss one possible approach: enhanced rock weathering. “We are trying to put the silicates in play, Earth’s largest alkalinity resource,” he said, referring to his work.
Natural rock weathering plays an important role in the carbon cycle—in simple terms, by neutralizing carbon dioxide dissolved in water and trapping it in bicarbonate minerals, which are ultimately buried in the ocean. But the natural process is incredibly slow; combating climate change requires a quicker fix. Enter enhanced rock weathering, wherein users jump-start rock weathering by grinding alkaline minerals into powder. Based purely on surface area, such particles should release their carbon-combating cations more quickly than their coarse counterparts.
Still, the tiny rock bits dissolve too slowly.
“There is this large-scale quest going on in the field for rapidly dissolving minerals, and they just don’t exist naturally because they have already dissolved,” Abby Lunstrum, a geochemist at the University of Pennsylvania who kicked off the session with an overview of the field, told C&EN.
“What can I do to make a mineral more reactive?” Kanan asked while presenting. “Ultimately you have to do chemistry.”
That’s exactly what Kanan did in 2025. He discovered that when a calcium oxide source (limestone) is mixed with magnesium silicate minerals and heated, the mixture reacts to form magnesium oxide (periclase) and calcium-rich silicate minerals (Nature 2025, DOI: 10.1038/s41586-024-08499-2). With the correct ratio of starting materials, Kanan was able to make periclase and the calcium-magnesium silicate, monticellite, a mixture he dubbed Monti. Both mineral types weather orders of magnitude faster than magnesium silicates, effectively unlocking an abundant source of alkalinity for enhanced rock weathering.
Kanan and his team further tested Monti as an alkalinity source with the help of the philanthropically funded Carbon Drawdown Initiative. The organization hosts “one of the largest and most heroic mesocosm studies” ever done to understand enhanced rock weathering, he said. Each mesocosm acts as a bucket-sized simulation of a field site. It gives the researchers a way to measure key indicators of enhanced weathering in the water that leaches out of the soil, including alkalinity and dissolved inorganic carbon.
Kanan has only recently started to share his mesocosm data. “You see a very robust weathering signal with these materials added to soil,” he told C&EN.
In fact, the dissolved inorganic carbon that leached from the mesocosms amended with Monti corresponded to an average removal of 4.18 metric tons (t) of CO2 per hectare over 42 weeks, Kanan said. In contrast, the same amount of limestone removed only 0.49 t of CO2 per hectare in the same time, and the basalt mesocosms had no significant increase in dissolved inorganic carbon. Basalt is currently the most common feedstock for enhanced rock weathering.
Now, Kanan wants to scale. He and a collaborator recently founded Mafix, a start-up that will partner with a cement manufacturer to create an abundance of Monti to use in field trials. And they’ve reached out to farmers and agronomists to collaborate. Ultimately, they want to validate that the weathering they see in the mesocosms translates to the field, he said.
Kanan’s approach “makes great progress in speeding up the weathering rates,” Lunstrum said. But it doesn’t address the problem of alkalinity loss across a landscape; it doesn’t matter how much alkalinity a material releases if it all washes away. It’s “a big issue that Earth scientists and environmental geochemists need to figure out,” she added.
