We are closing in on zero-carbon cement
The cement industry, responsible for roughly 8 percent of total global carbon emissions, is notoriously difficult to decarbonize. But a new startup, Sublime Systems, aims to manufacture zero-carbon cement that can easily be substituted for the traditional version. In this episode, Sublime CEO Leah Ellis talks through the company’s vision and process.
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David Roberts:
Of all the so-called “difficult to decarbonize” sectors, cement is among the most vexing. Making cement produces CO2 not merely through fuel combustion (in kilns that reach temperatures of up to 1400 C), but also through chemical processes that split CO2 off from other molecules. It is responsible for roughly 8 percent of total global carbon emissions.
Most gestures at decarbonizing cement to date are fairly desultory — things like adding special additives or injecting a little CO2 when the cement is mixed into concrete. The only widely available method that could theoretically produce no- or low-carbon cement is post-combustion carbon capture and sequestration. And there are plenty of people who would question whether that's actually viable at all, much less widely available, given that it would roughly double operational costs for a cement plant.
There are lots of startups out there attempting to solve this problem (as reported by Canary last month). Perhaps the most intriguing is Sublime Systems, a team that has developed something truly new and exciting: a system for manufacturing cement that requires no high heat (thus no combustion emissions) and uses inputs that contain no carbon (thus no chemical emissions). That makes the cement, at least potentially, not just low-carbon but zero-carbon. What’s more, the company says that, in form and performance, its product is a perfect drop-in substitute for traditional Portland cement, so it wouldn't even require any changes in the construction industry.
A carbon-free drop-in cement substitute — at scale and at competitive cost — would be genuinely transformative. I contacted Sublime CEO Leah Ellis to talk about cement chemistry, the company’s process, and the plan for reaching megaton scale. This one was truly fascinating and educational for me; I think you will really like it.
All right then. Leah Ellis, CEO of Sublime Systems, welcome to Volts. Thank you so much for coming.
Leah Ellis
Thank you so much for having me.
David Roberts
I'm excited today to talk about concrete, everybody's favorite subject. But first I wanted to ask you, I know you and your partner originally were trained as and educated as battery scientists. I'm just curious how you ended up here. What drew you into this area, this problem?
Leah Ellis
Yeah, my co-founder is a professor at MIT, Yet-Ming Chiang, and he's in the material science department, and I'm a chemist by training. I like to think of chemistry as the central science that combines everything from physics to biology. All of the good stuff you can sort of spread into anything from a foundation in chemistry. So I did my PhD in lithium-ion batteries. I worked with a prolific inventor, Jeff Dahn, and after that I wanted to continue working with an inventor. As you may know, in academia, there are so many different styles of research.
I mean, some people like microscopy and mechanisms, but I really like the creative aspect, like discovering something that could be useful or to solve problems. And not many academics and professors think through that lens. So I've always been very lucky to work with prolific inventors, both in my master's and my PhD. So for my postdoc, I sought to work with peop
