A startup is aiming to develop clean cement production technology and a low-carbon product. Sublime Systems is developing a revolutionary technology for decarbonized cement that eliminates the need for kilns and the use of fossil fuels in the production cycle of cement.
The startup founded in 2020 announced on January 17th it has closed a $40 million Series A funding round, led by climate-tech-focused fund Lowercarbon Capital with participation from existing investors like the Engine, Energy Impact Partners and others.
Southwest Asia’s leading cement producer Siam Cement Group is becoming a strategic investor. Sublime Systems will use the new capital to ramp up production at its pilot plant, build its team, conduct product testing, and advance offtake commitments from new customers and partners.
Sublime was only founded in 2020 and is spun out of the Massachusetts Institute of Technology. Co-founders are Yet-Ming Chiang – an MIT professor and co-founder of several climate-tech companies like A123 Systems, 24M Technologies and Form Energy, and Dr. Leah Ellis – an Activate Fellow and one of MIT Technology Review’s 35 Innovators under 35.
The company’s technology is unique and revolutionary as it replaces kilns – the most energy and fossil-fuel-intensive part of the traditional cement manufacturing process. It uses an electrolyzer instead of kilns that makes cement at ambient temperature from a variety of abundant calcium sources.
The company makes calcium in a form that is ready to react with silicon – the key element in sand. Normally limestone that contains calcium is superheated inside a kiln to about 2,700 degrees using normally coal for fuel – a process that releases tons of carbon dioxide into the atmosphere.
Sublime’s technology avoids both the use of kilns and thus fossil fuels needed to fire the process and the release of CO2 from limestone. It is the first company to produce cement through a technology that eliminates emissions from limestone and fossil fuels.
One step of the cement-making process, which Sublime is yet to master, involves processing the silicon into a reactive form. Silicon in sand is highly stable, so it is difficult to make it reactive. Sublime’s founder Yet-Ming Chiang claims there’s some early research showing it can be achieved.
For this purpose, Sublime Systems is using reactive silicon available in nature. Some examples of what the company might be using include calcined clays, coal ash, steel slag, and minerals like olivine.
Sublime’s cement is essentially sold as a mixture of the reactive calcium and reactive silicon. When water and gravel are added, the chemical reaction begins and the mixture starts to harden into concrete. According to the company, the approach is viable and scalable, and the cement has the same or better strength, slump, and durability than today’s portland cement.
So far, Sublime makes 100 tons of its low-carbon cement annually at a small facility. The $40 million raised will serve the company to scale production to as much as 40,000 tons a year by 2025, depending on its success in creating reactive silicon from nature.
In the meantime, Chiang says Sublime is working on scaling the process to make synthetic reactive silicon. According to the startup, there’s a long way to go to prove the technology can work at scale, but it is aiming for a commercial-scale plant by 2028.