The production of cement, the binding ingredient in concrete, is estimated to produce about 8 percent of the world’s greenhouse gas emissions. The part of the cement production process that requires the most energy and fossil fuels is the kilns used to heat up limestone and clay.
Sublime Systems, a startup that spun out of MIT in 2020, has found a way to replace the kiln with an electrolyzer that can make cement at an ambient temperature from a variety of calcium sources. In addition to eliminating emissions from the high-temperature kilns, this process also eliminates emissions from limestone.
Sublime Systems announced Wednesday it raised $40 million to accelerate production at its pilot plant at Greentown Labs in Somerville. The plant is producing up to 100 tons of cement per year. The company also plans to undergo product testing, secure advance agreements with customers and build its team from 30 to 70 employees.
The Series A financing round was led by Lowercarbon Capital with participation from The Engine, Energy Impact Partners and others. Siam Cement Group, the largest cement producer in Southeast Asia, joined the round as a strategic investor.
“Low-carbon cement is critical to build a decarbonized economy,” Sublime Systems co-founder and CEO Leah Ellis said in a statement. “We have successfully demonstrated the viability and scalability of our approach and we are able to produce cement with the same or better strength, slump and durability than today’s portland cement. The support of our talented team and capital from our investors will enable us to operate our pilot facility, secure advance offtake agreements and work toward producing our low-carbon cement at scale.”
Sublime Systems is one of several tech companies working to decarbonize cement production from a variety of different angles.
Colorado-based Terra CO2, for example, raised $46 million last year for its technology that can create cementitious materials from local feedstocks and waste products.
New Jersey-based Solidia Technologies and Canada-based CarbonCure, meanwhile, are infusing carbon dioxide into the concrete mixing process. This process creates calcium carbonate, which strengthens the concrete and allows producers to use less cement as a binder.
Oakland-based Brimstone raised $55 million last year for its process that replaces limestone with calcium silicate rocks, which have no embedded CO2. This new process also produces magnesium species, which passively absorbs CO2.
Compared to methods that use carbon capture and carbon sequestration, Sublime states that its cement is economical and uses less energy and has less embodied CO2.
“Sublime’s technology has cracked the code for low-carbon cement,” Clay Dumas, a founding partner at Lowercarbon Capital, said in a statement. “We review countless investment proposals and Sublime’s decarbonized cement offers many advantages over competitors not only for emissions reduction potential, but also for ability to deploy. The team has a clear path toward commercialization and is set up to execute and scale.”
Sublime is currently hiring for roles across engineering, operations and other departments.
