The Stanford spinout will use its pre-seed round to make 1,000 tons of a silicon fertiliser that feeds crops and removes carbon dioxide, produced with spare capacity in existing cement kilns.
Mafix, an agricultural technology start-up, has raised $5.4 million in a pre-seed funding round. The money will go towards scaling production of a silicon fertiliser designed to improve soil and crop health while removing carbon dioxide from the atmosphere.
Azolla Ventures led the round. Counteract VC, the Astera Institute, Plug and Play Ventures, Impact Science Ventures and a Dutch family office also took part.
Mafix will use the capital to produce 1,000 tons of its fertiliser as a commercial demonstration, and to develop its mineral conversion process for a wider range of feedstocks and next-generation products, including applications outside agriculture.
Making slow rocks weather fast
Enhanced rock weathering removes carbon dioxide by spreading alkaline rock across land, where it reacts with CO₂ and locks it away. Conventional approaches crush and scatter common rocks such as basalt. The limit is speed, because the minerals in those rocks weather extremely slowly.
Mafix says its process converts inert silicate rocks into fast-weathering minerals, so carbon removal happens within a single growing season. Applied as a fertiliser, the minerals release nutrients into the soil while removing CO₂ as stable bicarbonate.
The company launched in 2026 as a Stanford University spinout. Its founders are Jade Marcus and Dr Matthew Kanan, a chemistry professor at Stanford.
Cement kilns as the production route
The production step is designed to run inside cement plants. Mafix describes it as a drop-in process that works in existing kilns, so the company can take up spare capacity instead of building new facilities. That matters for cost, and for how quickly supply can grow.
Demand for silicon fertilisers already exists, according to the company, though producers can’t reliably obtain high-quality supply at a workable price. Mafix pitches its product to farmers on nutrient value and permanent carbon sequestration together.
Two markets, one product
Jade Marcus, chief executive and cofounder of Mafix, said: “The alkalinity trapped inside silicate rocks is one of the largest untapped resources on the planet. Our breakthrough is releasing it deliberately and quickly, transforming the most abundant rocks on Earth into a fertilizer that feeds crops and permanently removes CO₂ at the same time.”
For investors, the dual revenue model is the main argument that enhanced rock weathering can grow without depending entirely on carbon credit prices.
Jillian Chase, principal at Azolla Ventures, said: “Mafix’s silicon fertilizer is designed to improve soil health and agricultural productivity while delivering a scalable solution for permanent CO₂ removal, addressing two critical global challenges with a single technology. Its use of existing cement infrastructure for manufacturing means it can scale quickly to address farmers’ immediate needs while Jade, Matt and the impressive Mafix team develop additional products via their mineral transformation technology.”
What comes next
The 1,000 ton run is the near-term test. It will show whether the converted minerals weather as fast in the field as Mafix expects, and whether farmers see the yield benefit the company describes. Beyond that, Mafix says it wants to apply the same mineral conversion process to a broader range of feedstocks and to products in markets outside agriculture.
