Concrete is the most widely produced material on the planet—and cement, the glue that holds it together, is one of the most polluting, responsible for 8% of global emissions. While multiple startups are working on ways to reduce those emissions, Sublime System’s tech is one of the cleanest: It eliminates emissions completely by using an electrolyzer and calcium silicate rocks instead of CO2-emitting limestone.
In 2023, Sublime’s cement was certified to meet standard building codes. It also scaled up its pilot plant and began shipping the first bags of its product to customers for infrastructure projects in the Boston area, with the first commercial pour happening earlier this year. It can produce 250 tons of cement a year now; the next facility, which it aims to open in 2026, is designed to produce tens of thousands of tons.