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This company has created a recipe for carbon-zero cement

JUANA SUMMERS, HOST:

Roughly 8% of the world's total carbon emissions come from making one thing - cement. Cement is a key ingredient in the 30 billion tons of concrete that the world uses each year. And because of all that global demand, startups are trying to figure out different ways to make cement to reduce its carbon footprint. Emily Pontecorvo wrote about it for the climate news site Heatmap News. Emily, welcome to ALL THINGS CONSIDERED.

EMILY PONTECORVO: Hey, Juana. Thanks for having me.

SUMMERS: So, Emily, help us understand this. Why exactly does cement production release so much carbon pollution?

PONTECORVO: Well, there's one big reason, and it's that most of the emissions from the production of cement do not come from burning fossil fuels. They actually come from this chemical reaction that's fundamental to the process of making it. So to make cement, you basically take limestone, which is this very abundant mineral that's very cheap and easy to find, and you put it in a kiln, and you heat it up to really, really high temperatures. And that limestone contains carbon. And when you heat it up, you're basically trying to boil off that carbon. And that just gets released into the atmosphere. And so one part of the problem is heating this kiln, because today we use coal and gas and other fossil fuels to heat the kiln. But even if you take those fossil fuels out of the picture and you use clean electricity, let's say, you would still have carbon emitted by the process.

SUMMERS: You wrote in your piece for Heatmap News about this Massachusetts company called Sublime Systems that's trying to find a way around this to make low-carbon cement. Tell us, what is this company - what are they doing differently?

PONTECORVO: So the main thing that Sublime is doing differently is instead of heating up rocks in a kiln, they are driving this whole chemical reaction with electrical currents and water. And basically, because they're approaching it that way, they're able to use other kinds of minerals that don't contain any carbon. So not only are they avoiding the emissions from the kiln from, you know, burning fossil fuels, but they are also able to use these other materials that when they drive the chemical process, they don't release any carbon emissions.

SUMMERS: So, Emily, does cement that's produced using this new method - does it have the same performance as conventional cement?

PONTECORVO: Yeah. So this is a really crucial question because, you know, we've basically just been using this same recipe for cement for, like, 200 years. Sublime has already received a key certification that says their cement passes a number of strength and durability tests, and that means it can be used in the real world. The company's CEO, Leah Ellis, told me that it isn't in any real world projects yet, but it, you know, can be. And they're kind of working with partners to continue to test its durability and strength.

SUMMERS: And there's, of course, a question of cost here. Building is incredibly expensive. So I'm wondering, can this new cement compare with traditional cement on a cost basis?

PONTECORVO: Yeah, that's really tough. I mean, right now, you know, it can't compete. Electricity is still much more expensive than burning coal in a kiln. But the company hopes that, you know, in a future world where you're either, you know, penalized or there are regulations around the carbon intensity of your building materials, that, you know, in that world, it will be much more competitive.

SUMMERS: You've written that this company, Sublime Systems, is scaling up from a 250-ton pilot project to a 30,000-ton plant, which is significant. That said, that is just a tiny fraction of a percent when it comes to annual global cement production. So how long do you think it will be before techniques like this can scale up to meaningful levels?

PONTECORVO: You know, they call cement - scientists and researchers, they put it in this category of industries called the hard-to-decarbonize industries 'cause these are just really challenging problems to reduce these emissions without, you know, greatly increasing the cost of the products. And I think, you know, even though we have solutions like Sublime and what they're doing and what a lot of other companies are doing, it's still going to be, you know, potentially decades before these solutions are cost-competitive and at a scale where they're really making a difference.

SUMMERS: Emily Pontecorvo of Heatmap News - her piece is "A Sublime Solution To Climate's Hardest Problem." Emily, thank you.

PONTECORVO: Thank you so much. Transcript provided by NPR, Copyright NPR.

NPR transcripts are created on a rush deadline by an NPR contractor. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.

Linah Mohammad
Prior to joining NPR in 2022, Mohammad was a producer on The Washington Post's daily flagship podcast Post Reports, where her work was recognized by multiple awards. She was honored with a Peabody award for her work on an episode on the life of George Floyd.
Juana Summers is a political correspondent for NPR covering race, justice and politics. She has covered politics since 2010 for publications including Politico, CNN and The Associated Press. She got her start in public radio at KBIA in Columbia, Mo., and also previously covered Congress for NPR.
Christopher Intagliata is an editor at All Things Considered, where he writes news and edits interviews with politicians, musicians, restaurant owners, scientists and many of the other voices heard on the air.