Interview with Leah Ellis, Co-Founder and CEO of Sublime Systems #14
Electrifying cement production
August 26, 2021
This week, we’ll learn about concrete - more specifically about cement production.
We’ll start by having a short intro on the current way of making cement and the associated downsides.
Then, we’ll have an interview with Leah Ellis, Co-Founder and CEO of Sublime Systems. Sublime Systems is a Boston-based startup that is electrifying(!) cement production. Its electrochemical cell has the potential to cut the CO2 emissions of cement by 50-100%.
During the interview, it became undeniably evident that Leah is a climate-motivated inventor with courage. She used her knowledge and experience as an electrochemist in lithium-ion batteries to radically innovate cement production.
We chatted about Leah’s path from a scientist to a founder and how Sublime Systems is solving the problems of cement production to mention a few.
Leah was recently featured on the 35 Innovators Under 35 list by MIT Technology Review. So well deserved!
Before diving in, I recommend reading first the last week’s deep dive The Expedition #9: Concrete - the foundation of humankind. This will help you better understand the context of where Sublime Systems is operating.
Introducing Sublime Systems
The problem that Sublime Systems is tackling
Nowadays, cement production starts by putting limestone (calcium carbonate, CaCO3) and clay (silica-bearing material) into a big rotating cement kiln. This kiln is heated up to 1500℃.
The resulting material from the kiln, clinker, is then mixed with gypsum and supplementary cementitious materials. This mix is grounded into a fine powder we know as cement.
If you find the list of ingredients confusing, check out the logic tree of concrete’s ingredients on Miro. Hopefully this will help you to make more sense how the ingredients are connected.
Making cement emits CO2 in two main ways. Each way produces approximately half of the total CO2 emissions.
1. Decomposition of limestone (CaCO3)
When limestone (CaCO3) is heated up, it decomposes into calcium oxide (CaO) and CO2. This reaction is desirable to make the calcium oxide undergo further reactions with other minerals.
The CO2 emissions from the decomposition of limestone are inevitable as long as we use limestone as the source of calcium. The CO2 is chemically bound inside the limestone. To extract the calcium, CO2 gets released.
2. Burning fuel to heat the kiln
The limestone needs to be heated up to 1500℃ to initiate the decomposition. Heating up to this high temperature takes a lot of energy. The energy is generated by burning oil, gas, and coal, which all produce CO2 emissions.
The scale of the problem
Cement production is the third-largest emitter of CO2 emissions after fossil fuels and land-use change. In industry, it is the largest single emitter.
- 2.8 Gt of annual CO2 emissions (8% of all CO2 emissions!)
The scale of decarbonizing cement production is colossal.
Every year, our humanity produces 4 billion tons of cement. That’s 4 000 000 000 000 kg of cement. That’s the mass of 1 billion elephants. Wow.
Sublime Systems’ solution
Sublime Systems is producing cement electrochemically with the potential to lower the CO2 emissions of cement by 50-100%.
Sublime Systems has developed an electrochemical cell that decomposes limestone at room temperature.
The electrochemical cell can be powered by intermittent renewable electricity. This allows Sublime Systems to help smooth the grid and take advantage of the low-cost off-peak hours.
The reaction takes place at room temperature with renewable electricity. Therefore, the produced CO2 is 100% pure CO2 and at room temperature ready to be captured and stored.
Wisdom from Leah
What’s the founding story of Sublime Systems?
I have a Ph.D. in chemistry. In my Ph.D., I researched lithium-ion batteries and collaborated with Tesla and 3M to improve their battery chemistries.
After my Ph.D., I decided to do a postdoc. I went to MIT to work with Professor Yet-Ming Chiang, who is a famous scientist and entrepreneur having already spun out seven companies. I was lucky to get the Banting Fellowship for my postdoc, which granted me funding to work on anything I wanted for two years.
In the first conversation with Yet-Ming Chiang, he proposed that we should work on something radical. The improvements of lithium-ion batteries would be only incremental. That’s how we decided to work on electrifying cement production despite neither of us having a background in it.
I’ve always been climate motivated and wanted to be an inventor. Those motivators drew me to chemistry and entrepreneurialism. Chemistry and entrepreneurialism are powerful ways to make a dent in the climate change problem.
How is Sublime Systems’ process of making cement different from the conventional CO2 intensive way?
At Sublime Systems, we use an electrochemical reactor to make cement.
Our cell works similarly to a water-splitting (electrolysis) cell at a neutral pH. (Check out this video on standard water electrolysis in alkaline conditions, where pH > 7)
At neutral pH, you produce acid at one electrode and base at the other electrode. As a result, there is a pH gradient. This pH gradient lets us do chemistry.
We place the limestone in proximity to the acid that gets generated. When the acid reacts with the limestone, the limestone separates into calcium hydroxide and CO2. This reaction is similar to what you may have done or seen when kids put Mentos candy into a bottle of coke.
The calcium leaves our reactor as calcium hydroxide. It is already cementitiously active and ready to undergo further reactions with other minerals to become cement.
(If you want to dig deeper into the fascinating science behind Sublime Systems, check out Leah’s scientific article here.)
What advantages does your electrochemical way of making cement have?
Our technology holds several enormous advantages compared to the conventional way of making cement.
1. Operation at room temperature
Our cell can liberate the CO2 from limestone at room temperature. This much lower temperature enables us to use electricity to power the cell and save vast amounts of energy.
2. Use of intermittent renewable energy
Electrochemical reactors have a wide range of acceptable current densities. The wide range allows us to dial it up and down almost instantaneously with the supply of renewables.
We hope our system will also smooth the grid by taking some of that off-peak electricity input. In this way, you don't have to curtail your wind turbines when there is less demand.
3. Easy CO2 capture
The CO2 capture is an inherent part of Sublime Systems. The liberated CO2 is 100% pure and at room temperature, and so we can easily capture it.
When you heat up the cement kiln up to 1500℃ with fuel, the flue gas has a lot of impurities. It’s not pure CO2 and also contains other compounds like nitrous oxide. Furthermore, the flue gas is very hot. These make the carbon capture hard when conventionally making cement.
At what stage is Sublime Systems now?
We spun out of MIT in March of 2020, just as the pandemic was starting.
We've raised some seed funding from philanthropic venture capital and very mission-oriented VC.
These types of VCs, like Lowercarbon Capital and Prime Impact Fund, want to make a financial return but also want to change the world for the better. As a result, they are willing to wait a longer time to see a return on their investment.
This seed funding has allowed us to build a team. We are working at Greentown Labs, the largest climate tech incubator here in the US.
We focus now on scaling the production with our technology. We have already got our production of cement from grams to kilograms. Now we are working to go from kilograms to tons of cement.
Cement production is perhaps the only industry where the smallest pilots are made in mere tons.
Have you already entered partnerships with the cement industry players?
We haven't thought of partnerships with cement producers yet. We want first to make sure that we have demonstrated our technology well, especially that there are so few cement companies.
The world cement market is dominated by just a handful of international companies like LafargeHolcim, Heidelberg, and Cemex.
You’ve turned from a scientist into a founder. What things have you learned?
As a founder, one of the most important things is clear communication. A founder should be able to explain the work simply so that everybody understands it right away.
Chemistry is very complicated. It’s a complex field that is not easy to explain to your grandmother or siblings if they’re not chemists themselves. That’s why you have to pay attention to talking about your work understandably.
In academia, you don’t need to pay as much attention to communication, as everyone in the small group of experts understands your work very well.
What could academia do to encourage more scientists to spin out companies?
One problem with academia is that the professors have often never been anywhere except another university professionally. So they're training you also to become a professor.
It's very rare to find a professor in the sciences who came from industry or was part of a company or a startup.
The professors should have a more diverse professional background.
The other problem is that you don't learn much about industrial chemistry like cement or steel making in your chemistry degree. So you are not given a broad understanding of these chemistries that are so important in our society.
I wish there had been more focus on industry and applicable chemistry and less so on esoteric academic chemistry in my chemistry degrees.
What advice would you give to future or current climate tech founders?
For anyone who has a background in chemistry, open Wikipedia and start learning about new things. Try not to be intimidated by the invention process, but rather be open to it.
You don't have to be an expert in the things that you invent around. For example, aluminum smelting was independently invented by two 19-year-old boys who were just playing with different aluminum chemistries on their own time. Neither was I an expert in cement when I started my research on electrifying it.
You're likely to innovate if you come from a fresh mindset without any inherent limitations. If you are always looking for it, it will come to you.
I found it absolutely amazing what Leah and Sublime Systems are developing. I hope you got inspired and learnt a lot about cement production and how it can be changed to a better!
As always, feedback and ideas are warmly welcome via email@example.com.
Until next week!