Pushkin. You know it's amazing cement. Cement doesn't burn or rust or rot. Cement lasts for thousands of years. See Roman aqueducts, Mayan temples, and you can use cement to build almost anything. Cement is so amazing that every year humanity makes four billion metric tons of it. That is roughly, very roughly a thousand pounds of cement for every man, woman and child on planet Earth every year. Now, for the bad news, making cement is wildly, almost absurdly carbon intensive.
We don't hear so much about this. Cement is generally not what we talk about when we talk about climate change. But in order to solve climate change, we're going to have to figure out a better way to make cement. I'm Jacob Goldstein and this is What's Your Problem, the show where I talk to people who are trying to make technological progress. My guest today is Leah Ellis. She's
the co founder and CEO of Sublime Systems. Lea's problem is this, how can you make cement without emitting carbon dioxide? Before she got into cement, Lea was in grad school working on lithium ion batteries, and as happens to a lot of grad students. She had this kind of deflating conversation with her advisor.
One of my last you know, walk and talks with my PhD supervisor is like, you know, what's next in batteries? And he was like, oh, it'll take you know, tens of thousands of people ten years to get to the next level.
But I was like, oh.
Damn, Like I don't want to be like one of ten thousand people working for ten years.
So you realize that you sort of missed the kind of innovation glory days for batteries perhaps, So what do you do?
Well? I wanted to continue working with inventors, so I got a Canadian government fellowship to go anywhere work with anyone, and I chose to come to Mit to work with Professor Yetmingchek. And it was actually Yet's idea to work on cement. And it wouldn't have been something that I would have ever had the audacity to jump fields like that.
So how did that idea come up?
Well, so Yet a year before, in twenty seventeen, had spun out Form Energy, which is a long duration energy storage company, and he had his eye on these trends, you know, renewable electricity is becoming the cheapest form of electricity, especially if it's intermittent, and you know, the utility sector being thirty percent of house gas emissions, like, thought's going to go to zero if we'ever going to achieve net zero, and then you know what what would happen as a
consequence of that is that you have all of this renewable capacity that then you then you can use to decarbonise the next largest tranches of emissions, so cement and steel being each about eight percent of global CO two emissions. The thinking was like, you know, how do you decarbonise cement assuming you are in a world with abundant and relatively cheap renewable electrons.
So super top down, super like macro big picture, not like, oh, I've got this little technical idea, how can we build it up? But it's like, Okay, I'm I'm looking at the whole planet for the next thirty years, and I see that like making steel and cement is like a problem we have to solve, and we're gonna have a lot of intermittent clean energy.
What do you got exactly?
And so he mentioned cement to you, what do you know about cement. When he mentioned cement.
Well, I assume that cement and concrete were the same thing. I mean, that was my level of understanding at the time. But I did know that cement was, you know, a much larger tranch of COTO emissions than you know, lithium ion batteries could ever address.
And so just to be clear, when you say you assume that cement and concrete were the same, you're saying you didn't know anything. Because that's one that's always been hard for me. I memorized it in preparing for this interview. It's one thing I'll definitely get out of this AMA.
Yeah, and you know sometimes I get those two words mixed up even now.
So what's the difference just for everybody?
So, cement is the glue, it's rock glue, and concrete is the glue plus aggregate. So cement is the glue that holds the rocks together to meet concrete.
Right, So all the things around us are built out of concrete, and cement is sort of the essential ingredient in concrete.
That's right, It's about fifteen percent of the concrete.
How do you start learning about cement?
Well, I first started on Wikipedia. It's one of my favorite always to spend time.
So it was quite delightful.
And from Wikipedia, you know, spent a lot of time at the library, you know, in textbooks and then going from textbooks to research articles and.
Yeah, it's been really really fun.
Honestly, lithium ion batteries are art cool and magical, but cement is is awesome. I think if you're a material scientist, if you're a nerd, there's like a very deep and exciting rabbit hole that you can go down to you once you start getting stoked about cement.
Well, let's get stoked about cement. So first of all, it's extraordinarily ubiquitous, right, like so ubiquitous you don't even
notice it. I was actually listening to an interview with you a couple of weeks ago, and I happened to be at the airport, and I realized as I was listening, like I was of course standing on on cement on concrete right on the sidewalk, but also there were like I was it was like two decks, you know, arrivals and departures, and so there were these like columns made out of concrete, and then there was concrete over my head. So I was essentially like encased in cement in concrete
as I was listening to it. So that was good. That was that was getting me in the right in the right mood for this interview.
Yeah, once you see it, you really can't unsee it, and it's it's really fun. And as I've gotten into cement chemistry and durability and testing every sort of feature in the cement you look at you can see weathering, you can see freeze thought damage, you can see alkali silica reaction, you can see rebark corrosion, and it really makes uh, you know, a walk down the concrete jungle a little bit more intellectually stimulating than it was before.
So certainly there's a lot of it. Certainly it's important. And so let's talk about how cement is made today. This is not what you're doing, but sort of the thing you're trying to improve upon. Right, Portland cement is this phrase that it's basically a technique for making cement. Right, it's a product, but it's also a way of making the product that's been around for what more than one hundred years? So briefly, what is Portland cement? How do you make it? What do you start with.
Yeah, Portland cement is a specific formulation of cement that has been around one hundred and ninety nine years. So Portland cement will celebrate its two hundredth birthday this year on October fourth.
That's two hundred years since, and.
You're trying to make sure it doesn't make it to two hundred.
And fifty, right, exactly. Yeah.
So the way Portland cement is made, you take limestone as the calcium source, and then you will also need the right ratios of calcium to silica, alumina and iron. So that Portland cement recipe is about getting those ratios right. But the dominant ingredient is limestone.
So limestone is the key ingredient. The thing we want in the limestone is the calcium. But is the calcium bound with carbon? Is that our fundamental problem?
That's right.
So the limestone is a calcium oxide bound to CO two and those are chemically bound very strongly, which makes the calcium inert.
And the process of making cement is you want to essentially isolate the calcium, I mean, among other things, but a key piece of the process is that, right.
Yeah.
Okay, So in making Portland cement, how does that.
Happen by heating it to the point where that bond breaks and CO two, you know, goes as a gas and then you get this solid solid gas separation where you have solid calcium oxide and gashous CO two.
Okay, And so then that CO two just goes off into the atmosphere, go often to the chimney.
Yeah, it's mixed with the combustion emissions and goes into the air.
Okay. So it's just it's just more carbon emissions. It's bad. It's the thing we're trying to get rid of on the planet.
Yeah, that's right. Mean it's causing global warming.
Okay. So you've broken down the limestone and emitted a bunch of CO two in so doing, but you're not done yet, right, what has to happen next.
So once that's broken down, it's heated further to fourteen hundred degrees celsius.
So it's getting wildly hot. I mean, is the rock actually like melting? Does it look lava ish if you look at it?
Yeah?
And I actually have had the distinct privilege of looking down the center of a Portland cement kiln. There there's like a tiny hole under the fuel injection port, you put on a welding mask. It's of course extremely hot, and you can peer down and see the rotary kiln going. You can see the flame coming right over your head through that fuel injection port, and you can see the molten rock rolling towards you, like red red, glowing hot.
And so so, in addition to the carbon dioxide emitted directly from the limestone in the first stage, presumably people are burning a lot of fossil fuels in order to make this rock lava hot in this stage, thereby emitting more carbon dioxide into the atmosphere.
That's right.
And so besides, every Portland cement kiln you're going to see, you know, a small hill of coal, and it's normally bitchumen is coal, though there's often a blend of fuels used to heat up the kiln to this enormous temperature. But bitchumen is cool. Is what's necessary to get this like highly luminous flame that creates the ideal temperatures.
So you're not only burning fossil fuels, you're burning coal, which is a particularly dirty, particularly carbon intensive fossil fuel.
That's right.
Yeah, And we make a ton of cement, so like cement. It's like very carbon intensive, emits a lot of carbon into the atmosphere, and we need it, and we make literally what order of magnitude how many tons?
Yeah, about four billion tons a year.
Four billion tons a year. And so overall, when you take it all together, what percent of human carbon emissions are from making cement?
So it's eight percent of global CO two missions from cement.
This is a big problem, and we don't know how to fix.
It, that's right.
So there are incremental approaches that chip away at the problem, like using alternative fuels. You can swap out some of the coal with natural gas or with burning tires. You can use supplementary sumuntitious materials, so some antigious materials that are less performant, you can blend them in up to thirty even up to fifty percent to to you know, reduce the emissions. But getting to zero is very difficult, if not impossible, with things that are exist today.
So let's talk about that, right you You are not going for an incremental gain here, you're saying, okay, let's start from zero and let's figure out a whole new way to make cement that doesn't emit any carbon dioxide and you decide that instead of using coal, you're gonna use electricity, right.
That's right.
So being battery scientists and electric chemists, you know, we've got the hammer and everything looks like a nail, right, so we can's electricity, but we wanted to look beyond it. Just the most obvious way, which is like to use an electric kiln for heating, that's got as challenges. I mean that one's the obvious way. If it was easy, people would already have done it. There's various challenges with efficiency and material so we had to find another path.
And what we derived after many brainstorming sessions and investigating different options, was this way of breaking down the minerals using electric chemistry instead of using heat. So by bypassing the heating also allowed us to be more amenable with the use of intermittent renewable electricity, because of course heating
requires base load electricity. It takes days to heat up a kiln to those high temperatures, and so it doesn't allow you to be rampable, it doesn't allow you to be load following.
Right, because that a regional kind of marching orders. The original big idea was like we're going to have extraordinary abundance of renewable energy, but for a while at least, it's going to be intermittent. The sun's going to shine, then the sun's going to go down, and so you you don't want to build a system that requires constant high inputs of power over days and days, because that doesn't fit the kind of worldview you're building for.
Well, yeah, that's right. But also you can get a cost advantage. You can get the cheapest electricity if you can take it whenever it's available.
So okay, so go on.
The next thing you do is technoeconomic modeling. So start modeling, like what does it cost to do this, what are the inputs, what are the outputs, what's the you know, what's the capex, what's the opax, what's the labor, et cetera. Getting quotes from vendors for specific pieces of equipment, getting actual data from the pilot using actual numbers, and so now it's like this, you know, multi tab quilt sized spreadsheete.
But getting that going was the first step, because you know, that's what allows you to pivot quickly to see the weaknesses of your approach. And we continue doing that, and we still continue to do that to refine different elements of our process.
This process Leah is talking about, it's a whole new way of making cement. It doesn't involve heat at all, and Lea hopes it will be this turning point in the millennia long history of the way human beings make cement. In a minute, she explains how it works. So you've come up with this new process. You're still refining it, trying to make it more efficient, reliable, whatever, But how does it work?
Yeah, Basically we're breaking down the inert minerals using chemistry and electric chemistry instead of using heat. So you know, the heart of our system, or maybe call it the lungs, is this electrochemical reactor that takes neutral pach water and splits it.
Into acid and base.
So there's a pH gradient that forms between the two electrodes and that's used to dissolve calcium and other minerals
from rocks. So actually the electrochemical process we use since we're digesting the rocks instead of cooking them, we don't have to use limestone, so we're using calcium silicate minerals and industrial wastes and basically taking the rock and then splitting it into its mineral components, drying all those off into free flowing powders, and then reassembling a cement powder with the right ratios of all of these elements to make a high performance cement.
And so you basically use electricity to turn water a va of water into a place where like part of the water is somewhat acidic and part of the water is somewhat basic. And then you put the rocks into that water, and the acidic parts of the water do some of the words, and the basic parts of the water do some of the work, and you're wet, and you wind up with the minerals you need at a price you can afford.
Yeah, exactly. You said it very well, So I.
Know you start with the idea, and I've heard you say that. Initially you made one gram of cement, which is like you described it as like the size of an almond, which is particularly amazing given how heavy and big cement is. And then you did a kilogram. Where are you now?
We came out of stealth about a year ago after we built our pilot plant, which was initially sized to produce one hundred tons a year. In the past year, We've had about seven thousand hours of uptime. We've scaled it up to two hundred and fifty tons per year. We've produced tons of cement and have ran it continuously under dozens of conditions to you know, optimize it.
And that cement you've produced is it is it out in the world. Is it just like practice cement? Is it real cement? You know, holding up a building somewhere or something?
It is actually holding up a building somewhere. So we did our first field poor about two weeks ago.
Oh congratulations, Yeah, I like that. For field poor. Where was the field poor?
It was in the Boston area and a piece of in a in a commercial construction project. It was going underneath the construction. It's typically what's called called a mud slab.
So yeah, so.
That's what you're doing. Now, what have you not figured out yet? Like, what has to happen for you to get from here to being a real business selling lots of cement whatever all over the world or whatever for you to be a real business, for you to be a real business with revenue and your cement just you want your cubmit to be boring, right, you want your to be just like whatever boring again.
Yeah, well, there are certain things we figured out. We figured out the product, we figured out the pros us. But where we are today is still Even though I'm so proud of taking this from a gram to two hundred and fifty tons in four years, it's still a drop in the ocean. I mean, we affectionately call our pilot plant this cement plant for ants.
It has to be at least three times.
Bigger than this, but we have to get to a million tons per year.
We're going to compete on cost with.
Today's Portland cement, and so going from pilot scale to full scale, where full scale for cement is just a titanic colossal size, our next step is to build a minimum viable commercial scale plant. So we refer to this as our kiloton plant. We have a site secured in Holy Oak, Massachusetts, on the site of an old paper mill, which we are in the process of removing this ancient paper mill, but all the remnants of what makes this a really exciting industrial.
Site still exists. So a hydro electric.
Dam, ready, access to rail, ready access to a workforce, you know, industrial permits exist and so our next our next step is to wrap up the pilot phase in the coming months, do do the engineering and start procuring long lead equipment so that we can start building our plant. And so that is the work that you know, my colleagues in the office are busy doing right now.
So these are very like practical heavy industry, could be any kind of a big factory concerns. Do you still have engineering or technical problems to solve as well, or do you feel like you've got it down?
Well both, I do feel like I've got it down. I'd say, you know, the problems never stop and also the improvements never stop. So in the spirit of swift and massive, we move as quickly as we can to move from one one degree of scale to the next. But there's you know, I have to say, I have the distinct privilege of working with some of the smartest people I have ever met in my entire life, and I've had the pleasure of working with smart people all
throughout my education and career. But you know, we're generating quite a lot of IP, We're generating quite a lot of improvements. There's so many improvements that we're planning to feather in over time as we develop the system that I think will replace Portland cement in the next one hundred years.
And in terms of cost, I mean, obviously cost must be to a very large degree of function of scale. And you're scaling up at scale. Are you already cost competitive? Do you have to find new efficiencies? I mean presumably this is like a brutal commodity business.
Yeah, totally brutal.
And so we can get very close to competing on costs with Portland cement, no carrots, no sticks, at scale with six sons of kilawad hour electricity. So not even using funny math, so using what we think are you know, realistic assumptions, so you know, but we're still far out from a megaton plant. But what we can say with total confidence is that we will be cheaper than Portland cement plus post combustion carbon capture, which is presently the only other way to get to zero for cement making.
So every time you take a Portland cement kiln million tons per year, you add post combustion carbon capture, you add some other process. You're always adding capex to that Portland cement plant and opex. And I think the wonderful thing about Sublime, which is our unique advantage, is that we're not adding onto the kilm, we're replacing the kilm.
We're not capture, we're not storage, we're carbon avoidance, and that ultimately is much cheaper than capture and storage because you're not adding onto the system.
What are some reasons it might not work?
You know, it might There are one thousand ways to die, maybe even more, and I like to keep my eyes open to all of them. And we do quite a lot of risk registered development. We have like what we call our three a M list quarterly, I get, you know, everyone anyone in the.
Like what keeps you as you.
Worry about when you wake up at three in the morning. Yeah, what's at the top of that list right now?
If changes day to day. So I'm glad you said right now.
I mean, like, as we go into this process of going from pilot to first commercial, I think about cost overruns and this this isn't just you know.
Just like building a factory, totally classic.
And you know, hiring I'd love to hire someone who's done this before because I think this is where you really need someone who's done this before, because it's not just the cost of the thing.
I mean, we think.
We've got that lockdown with solid research, solid quotes, just timeline. You know, imagine like you're missing like some widget and you find out this little dinky piece is like I'm gonna show up a year later than everything else, and your companies, you know, you've got your burn rate of the whole company.
So that's that's just one way to die.
I mean, yeah, it's a classic. That is a classic way to die.
Yea running out of money. Your heart stops beating it, you know.
So that's the sad story. There is some happy story where it works and you build a factory and you start selling cement, clean cement. Like if you go I don't know, say ten years into the future, what does the world look like if it's the happy story.
Yeah, well I may go more than ten years in the future, and I maybe go one hundred years in the future. I like to think about a post carbon world, like what does it look like when you know, you know, you're penalized for your CO two emissions the same way you're penalized for you know, mercury emissions or something like that.
And you know, I like to think that if we're successful.
The most wildly successful version of Sublime Systems is that We've changed the way humans make cement the same way you know, Romans changed the way we made cement, same way the British and French with Portland cement changed the world way we made cement. I think, you know, humbly, cautiously, optimistically, what Sublime is doing could change the way humans make cement forever. And I think that's really exciting because it's
it's such a monumental thing. Like when you go to when you go to Egypt, you see, you know, construction, things that were made to last, you know, you go see the aqueducts, you go see things, and these things that were built are a testament and a monument to
the values of the people that created them. And so I think, you know, you know, the coolest thing for me is to have like enduring significant buildings that are made with you know, the cement of the future and having like archaeologists one thousand and two thousand years from now looking back and being like, oh, there was this period before where the world was a certain way, and then there was something that happened where co two levels crusted and then they came down and at that point
in time, like we can see how their buildings materials change to adapt to that.
I think. I think that's pretty cool.
I mean, I don't think you can get closer to a monumental legacy than to really change building materials in.
That way, the way literal monuments are built. Yeah, we'll be back in a minute with the lightning round. After that big think and we're going to do a small think lightning round to conclude. What's your favorite concrete structure or concrete thing?
Oh, you know, it's the things that folks on my teammates so often. You know, we're doing tests on our cement pace, and so we have a bunch of molds of like you know, frogs and dragons and snowmen and whales and turtles and so. I yeah, my favorite concrete things are it's probably the dragon.
I like the dragon the most.
How big is the dragon?
Oh?
It fits on the palm of my hand.
I sometimes take it with me to conferences, you know, just to meet people.
You know, seeing is believing, and so sometimes it travels with me.
What's your least favorite concrete thing?
I would probably say New York City.
Just something about that city just makes me despair. I don't know what it is like just never been a fan.
I'm trying.
I'm trying to be open minded about New York City, but you know, I fail each time I go.
No offense, not my cup of tea.
Fair. It's not for everybody. It's for millions of people, but it's not for everybody. So you rode your bike across Africa from north to south. What was the worst day of that trip?
You know, there were days when I was extremely sick, so it would probably be.
Those days.
And you still had to ride. Yeah, often, Yeah, Okay, what was the best day?
I mean, every day was the best day, even if I was totally sick.
I mean, I like to say that doing that trip across Africa, which was about four months, twelve thousand kilometers, about one hundred kilometers a day on average. I mean, it's something I would recommend both to my best friends and my worst.
Enemies, because.
I think it does is extremely character building, and you get very comfortable with discomfort, and you know, your pain tolerance gets through the roof. You become extremely physically fit. So yeah, even the good days and the.
Bad days, we're all character building.
As a chemist or as a material scientist, what do you think you understand about the physical world that most people don't.
Well.
A lot of people think chemistry is scary. I think people think chemicals are scary. I think chemistry is one of the most fascinating things you can do. Is like turning one form of matter into another form of matter by blending them together and heating them up and pressurizing them. Yeah. I'm always surprised when people say that they didn't like chemistry or they found it scary in high school.
To me, it's just pure magic.
I'm going to run my first marathon this year. I know you have run many marathons. What's one piece of advice you would give me?
Don't walk.
Once you start walking, like, you'll never be able to run again.
So even if you're you think you're if you're faced.
With a hill, you're like, oh, I could walk up that hill just as fast as I could keep running. Just don't let your body know that walking is an option, because you will end up walking those last five kilometers as I did first time I did the marathon.
That is good advice. Is there anything else we should talk about? Did we not talk about anything that we should talk about?
You know, I've.
Yeah, I mean one thing that I feel strongly about is carbon avoidance, and you know, this need to avoid carbon emissions, and I just believe so much, not only in my own technology, but but in others that are coming out in steel and ammonia and industrial processing.
That is about efficiency.
It's about doing things smarter and not making things more complicated, and it you know, I love nothing more than like really elegant solutions. I'm biased, but in my biased opinion, Sublime it's one of these elegant solutions that will be obvious in retrospect. And I think it's a very exciting time to be to be technologists, to work at startups, and to really force these new inventions into reality with help from the industry incumbents, which I think are moving faster than an ever before.
To create the future. It's a really fun time.
Pleiah Ellis is the co founder and CEO of Sublime Systems. Today's show was produced by Gabriel Hunter Cheng. It was edited by Lyddy jeene Kott and engineered by Sarah Bruguier. You can email us at problem at Pushkin dot FM. I'm Jacob Goldstein and we'll be back next week with another episode of what's your problem,