Sublime Systems’ low-carbon cement goes commercial

In early May, Leah Ellis, CEO of startup Sublime Systems, stood watch as crews poured and raked concrete at a construction site in Boston. Her company’s fossil-fuel-free cement had been used to make that concrete, and the moment marked an important milestone.

That’s because the three tons of cement in the concrete being formed into the floor of the indoor public space of One Boston Wharf Road, the city’s largest net-zero commercial office park project, was the first commercial application of Sublime’s product.

Trying to get the construction industry, which is known for being resistant to change, to embrace a novel form of cement is no small thing.

“Building owners don’t buy cement — they buy buildings,” Ellis told Canary Media. ​“Developers don’t buy cement — they buy concrete. And they buy it from the concrete subcontractor, who buys it from the ready-mix supplier. And there are a lot of providers in the value chain there that don’t get credit for using low-carbon cement.”

What those companies do get credit for is providing high-quality cement and concrete at reasonable cost, she said.

Sublime’s cement is made by electrically charging a bath of chemicals and calcium silicate rocks at its pilot plant in Somerville, Massachusetts. Last September, a key standards body determined that it met the same specifications as ordinary Portland cement, a material that’s produced by the hundreds of millions of tons each year in fossil-fueled kilns at temperatures as hot as molten lava.

Now Sublime is concentrating on getting the customers it needs to justify the next phase of its growth. In March, the MIT spinout won an $87 million grant from the U.S. Department of Energy to build its first commercial-scale plant in Holyoke, Massachusetts, capable of producing tens of thousands of tons of cement per year.

To finance the remainder of the Holyoke project, ​“it is critical for us to have advance market commitments,” Ellis said, to prove ​“there are people who want to use this material and will pay for it.”

“That’s why Yanni is so important,” she said, referring to Yanni Tsipis, the senior vice president at WS Development, the company developing the One Boston Wharf project. Tsipis, an MIT graduate and lecturer at the MIT Center for Real Estate, contacted Sublime after reading about the company in the MIT Technology Review.

“This partnership with Sublime is to demonstrate the power of the possible when innovation flows from incubation into industry,” Tsipis told Canary Media. ​“The location of this particular [concrete] pour will be experienced by thousands of people every day, and it’s a good way to share our aspirations.”

The plan for One Boston Wharf Road is to build and operate a 700,000-square-foot mixed-use office building with a greenhouse gas emissions impact that’s 90 percent below code requirements. To hit that target, WS Development is installing heat pumps designed to replace fossil-gas-fired boilers for heating large buildings, using the latest low-global-warming-potential refrigerants for its chillers, and contracting for renewable electricity to power the complex, he said.

While those choices reduce carbon emissions associated with building operations, low-carbon cement helps reduce the ​“embodied carbon” footprint of buildings. Cement production is responsible for roughly 8 percent of global carbon dioxide emissions.

Today, the primary way of reducing the carbon footprint of the concrete that’s made from cement is to blend in lower-carbon substitutes — supplementary cementing materials in industry jargon. But to tackle the emissions of cement making itself, the world’s largest producers have set their greatest hopes on carbon capture — an expensive and complex industrial-scale solution with unclear prospects over the next few decades.