Gaining Ground
What if farmers could use a fertilizer that mitigated climate change? That for every dollar you spent buying a soil additive, it led to two dollars in the harvest—and long-term carbon emissions removed from the atmosphere?
That’s the value proposition of Mafix, a startup that is translating science discovered in Professor Matthew Kanan’s lab at Stanford.
“I got really excited about the intersection of agriculture and carbon removals,” says Jade Marcus, CEO and cofounder of Mafix. As a PhD student, she joined the Kanan Lab in 2023 and contributed to a mineral conversion process that is now the venture’s core technology.
The Mafix soil amendment uses clever chemical engineering to form a calcium magnesium silicate that releases plant-friendly silicon while removing carbon dioxide (CO2) from the atmosphere in the form of bicarbonate ions. They believe this approach can be a gigaton-scale solution.
“Our novel IP is that we’re unlocking trapped alkalinity,” she says.
Faster and stronger
Mafix is improving the performance of a carbon removal technique called enhanced rock weathering, or ERW for short. Conventional ERW takes naturally abundant silicate rocks, grinds them up, and spreads them on agricultural fields, relying on increased surface area to accelerate a natural weathering process that normally takes millennia.[1, 2]
“Even with high surface areas, weathering with the feedstocks used today is just too slow,” says Kanan. “Studies of natural soils that have accumulated silicate dust for thousands of years, exactly the type of feedstock deployed in conventional ERW, show miniscule CO2 removal rates.”
The Mafix technology changes the underlying mineralogy of the rocks, generating a mineral structure that lends itself to fast weathering.[3]
“The existing enhanced rock weathering companies have done a really good job laying the foundation,” says Marcus. “I see us as complementary and solving a critical problem that they face now.”
An independent study found the Mafix product can capture on average 2.7 tonnes of carbon dioxide per hectare—in only six months. By comparison, researchers found that applications of crushed basalt rock—the most common material used in ERW—removed 0.03 tonnes of CO2 per hectare in the same time period.
Greenhouse growing studies of rice at Louisiana State University also demonstrated a 50 percent increase in grain yields using Monti, the Mafix fertilizer. The startup’s goal is to have farmers deploy Monti at rates similar to agricultural lime, up to 2 tonnes per acre.
Silicon is the second most abundant element in the Earth’s crust, but plants can only process it in a very specific form. “When you farm on the same acres year after year, you end up depleting the soil of plant-available silicon,” she says.
Already, farmers have asked to be early test users to benefit their crops. Silicon improves the structural integrity of plants, helping crops grow tall and not collapse. The mineral also helps plants absorb nutrients from the soil more efficiently, such as nitrogen, phosphorous, and potassium.
“So it’s a really important element from a crop resilience standpoint,” says Marcus.
Paving a path
From lab discovery to field studies, the Mafix team has needed to increase capacity year after year. To produce 100 kilograms, they bought a bigger oven for the lab. But to manufacture 1,000 tonnes? They’ve looked to cement manufacturers.
Clinker is a primary ingredient of cement, which, as a calcium silicate, is chemically similar to Mafix’s product Monti. Because cement manufacturers often have spare capacity on their units—on average one-third of the year globally—these companies are eager to partner. Meanwhile, using existing infrastructure increases the startup’s speed to market and decreases overhead expenses.
Funding from the TomKat Center, together with the Stanford Sustainability Accelerator, has enabled the startup’s progress to date—from funding more than a dozen field trials to connecting the cofounders with strategic partners. In the year ahead, Mafix is scaling up capacity and conducting a lifecycle analysis of Monti, from kiln to freight to fields.
“This is the next wave of products that can be both helpful from a food security standpoint, but also from a climate standpoint,” says Marcus. “Within five years, our goal is to have at least a megaton of CO2 removed per year.”
This article is part of the TomKat Center Spotlight series designed to highlight the impact and trajectory of the work of faculty and students who received funding through our Innovation Transfer Program, TomKat Solutions, and Graduate Fellowships. Stanford University does not endorse any non-Stanford entities, programs, products, or services listed in the article.
- Linke et al. Geochem. Perp. Let. (2024) DOI:10.7185/geochemlet.2415
- Li et al. Earth and Planetary Science Letters (2016) DOI: 10.1016/j.epsl.2016.03.015
- Y Chen et al. Nature (2025) DOI: 10.1038/s41586-024-08499-2
