Construction is a dirty business, but some companies are working to help clean up its act.
One such company is Sublime Systems, which recently announced, along with WS Development, the first commercial application of low-carbon Sublime Cement in One Boston Wharf — Boston's largest net-zero-carbon office building — in the Seaport District.
The concrete will be prominently located in the building's main public space. The Sublime Cement floor will be marked with educational materials explaining the significance of decarbonized cement in combating rising global temperatures.
"We and Sublime share the same vision and mission," Yanni Tsipis, senior vice president
at WS Development and lecturer at the MIT Center for Real Estate, said in the announcement. "We are developing the largest net-zero-carbon office building ever built in Boston, and now we have the opportunity to showcase the most forward-thinking low-carbon building technology on the planet in the public space, at the heart of this building."
"Buildings are monuments to the values of the people who build them, and the One Boston Wharf project represents WS Development's leadership in ushering in our post-carbon future," Sublime CEO and co-founder Leah Ellis said. "We are honored to have Sublime Cement featured so prominently here and are confident this pioneering place will inspire infrastructure owners everywhere to embrace low-embodied-carbon materials as a powerful tool for achieving our global net-zero goals."
Sublime Systems, which spun out of MIT in 2020, has electrified the cement manufacturing process, allowing it to make low-carbon cement that "performs like the building material you're used to, without the carbon emissions."
"In layperson terms, we often refer to Sublime as the electrical vehicle of cement making," Ellis explained to The Cool Down. "We are taking a high-heat, combustion-driven process and replacing it with an ambient-temperature one that relies on electricity. Our cement forms the same hardened concrete that the cement produced in the old, high-emitting fashion does, just the way EVs get the driver to where they are going as a combustion engine always has."
Concrete is the second-most used material on Earth, after water. Cement is the key ingredient in concrete and is responsible for about 8% of global planet-warming pollution. Ellis told TCD that traditional ordinary Portland cement (OPC) is made by decomposing limestone — a mineral that is about half carbon dioxide by weight — in a giant kiln powered by dirty energy.
The CO2 that this reaction releases and the pollution burning dirty energy creates add up to almost one ton of CO2 released into the atmosphere for every ton of OPC made. Sublime's electrified system avoids both sources of pollution.
The company's co-founders, Ellis and professor Yet-Ming Chiang, who were MIT battery scientists, created Sublime based on the idea that "increasingly reliable, abundant, and inexpensive renewable energy could be used to decarbonize the planet's dirtiest industries." This led them to the breakthrough manufacturing process they are commercializing.
While their product may be sublime, advancing the low-carbon cement market has been difficult. Ellis said a key hurdle is the construction industry's many stakeholders. Everyone, from owners to contractors, needs to see the value of the new material and work together to make the switch.
The partnership with WS Development and the Seaport pour were examples of just that, and Ellis said she hopes it will serve as a blueprint for how collaboration can improve the industry.
Sublime Systems developed the cement as a drop-in replacement for OPC in today's ready-mix concrete infrastructure. Ellis told TCD that means it can be milled, stored, shipped, mixed into concrete, and used in construction the way OPC is — without new infrastructure or operating procedures.
The company has worked to validate the product's performance by starting with smaller applications to deepen partnerships within the construction industry. It produces 250 metric tons (about 275 tons) per year out of its pilot plant in Somerville, Massachusetts, and will open in 2026 in Holyoke, Massachusetts, its first commercial plant, which will produce over 30,000 metric tons (about 33,000 tons) of low-carbon cement annually.
Long-term, the company will scale to 1 million metric tons (about 1.1 million tons) per year, putting it on par with today's cement plants. Because its process is one of carbon avoidance — not a net-zero process that cleans up pollution with costly carbon capture infrastructure — its cement will ultimately be the most cost-effective decarbonized option at scale. That will also allow the product to eventually be not only commercially available but also available to anyone looking for cleaner cement.
"We joke often that cement is everywhere yet invisible at the same time, which is why it's important to celebrate how it's used," Ellis told TCD while discussing the importance of Sublime System's partnership with WS Development and the Boston project.
"We know change doesn't come easy, but as a team, we aren't in this because it's easy, but because it's important," she added. "We hope something as simple as a gray slab of cement will inspire others to embrace their role in ushering in our world's decarbonization and pursuit of our net-zero-by-2050 goals."
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