Latest / The Manufacturing Podcast with Fexingo: Factories, Supply Chains, and Industrial Business / How a Swiss Factory Makes Cement That Absorbs Carbon
Transcript
- Lucas: Cement is the glue that holds modern civilization together, and it's also one of the dirtiest things we make. About eight percent of global CO2 emissions come from cement production, and the chemistry itself is the problem: when you heat limestone, you release CO2 as a byproduct. There's no way to just 'clean up' that chemical reaction. Luna: Right, it's not just about burning fossil fuels for heat. The process emissions are baked in. So what do you do if you can't avoid making the CO2? Lucas: You capture it and put it somewhere else. And one of the most promising places to put it is back into concrete. There's a startup near Zurich called Neustark that's built a factory doing exactly that. They take demolished concrete, crush it into a fine powder, and then inject that powder with captured CO2. The CO2 mineralizes — it turns into calcium carbonate, basically limestone — and stays locked in the aggregate permanently. Luna: So the demolition waste becomes a carbon sink. That's elegant. How much CO2 are we talking about per ton of aggregate? Lucas: About 40 kilograms of CO2 per ton of recycled aggregate. It doesn't sound like a lot, but their current plant processes 25,000 tons of demolition waste per year, which means they're permanently storing about 1,000 tons of CO2 annually. And they're scaling fast — they have multiple plants planned across Europe. Luna: A thousand tons is a drop in the bucket compared to global cement emissions — which are around 2.5 billion tons per year. But the beauty is that this is permanent storage, and it uses waste that already exists. It's not a silver bullet, but it's a real, measurable wedge. Lucas: Exactly. And if these conversations have moved your work forward or changed how you think about industrial innovation, we should mention: we deliberately don't run ads on these episodes. If you want to support that choice, the link is buy me a coffee dot com slash fexingo. Luna: Yeah, it's a small way to keep the show independent and ad-free. No pressure, just know it's there. Lucas: Alright, back to the Swiss factory. The really interesting part is the chemistry. The CO2 they inject is captured from a biogas plant — so it's biogenic CO2, not fossil-derived. That means the whole process is carbon-negative in theory: you're taking CO2 that was already in the short-term carbon cycle and locking it away for thousands of years. Luna: Wait, so they're capturing CO2 from biogas combustion and injecting it into old concrete? That's a loop. The CO2 came from plants, got turned into biogas, burned, captured, and now ends up as limestone in a new building. Lucas: Exactly. And that's key for carbon accounting. If you use fossil-derived CO2, you're just moving emissions from one place to another. But with biogenic CO2, you're actually drawing down atmospheric carbon because the plants pulled it out of the air as they grew. Luna: So the cement industry has a way to offset its process emissions. But how does the economics work? Capturing CO2 is expensive, and recycled aggregate is often cheaper than virgin aggregate. Can they make money? Lucas: That's the key question. Neustark sells the carbonated aggregate as a premium product — construction companies pay a bit more because it helps them meet sustainability targets. But the real revenue comes from carbon credits. If you can prove you stored a ton of CO2, you can sell a carbon removal credit for something like $100 to $200 per ton on voluntary markets. That margin is what makes the business viable. Luna: And that market is growing fast. Microsoft, Stripe, Shopify — they're all buying carbon removal credits. So Neustark is tapping into a demand pool that barely existed five years ago. Lucas: Right. And they're not alone. There's a Canadian company called CarbonCure that does something similar, but they inject CO2 into fresh concrete during mixing, not into recycled aggregate. CarbonCure is already in hundreds of plants. Neustark's approach is different because they focus on the demolition waste stream, which is a huge untapped source. Luna: So which approach is better? Injecting into fresh concrete versus into recycled aggregate? Lucas: They're complementary. CarbonCure can be retrofitted into existing concrete plants, so it scales fast. But the amount of CO2 you can inject is limited by the cement chemistry — about 10 to 20 kilograms per cubic meter. Neustark's recycled aggregate can hold more because the crushed concrete has a lot of surface area and porosity. And since recycled aggregate is often used as a replacement for virgin gravel, you're avoiding the emissions from mining that gravel too. Luna: So Neustark gets a double benefit: storing CO2 and avoiding virgin material extraction. But the challenge is that recycled aggregate isn't used everywhere yet. Builders still prefer virgin aggregate for structural concrete in many cases. Lucas: That's the next frontier. Neustark is working on getting their carbonated aggregate certified for structural use. Right now it's mostly used in non-structural applications like road base and backfill. But if they can get it approved for reinforced concrete, the market opens up dramatically. Luna: And that's where regulation matters. The Swiss government has been pretty proactive on circular economy standards. Do you think that helps Neustark's timeline? Lucas: Absolutely. Switzerland has a landfill ban for construction waste, so demolition material has to be recycled anyway. Neustark plugs into an existing waste management infrastructure. They don't have to build a collection network from scratch. That's a huge advantage over a startup that has to create its own supply chain. Luna: So the regulatory environment is almost as important as the technology. And speaking of technology, how much energy does the CO2 injection process use? If it requires a lot of electricity, the carbon math changes. Lucas: Neustark claims the process is energy-positive in terms of carbon. Their plant uses about 50 kilowatt-hours per ton of CO2 stored, which is minimal. And since their CO2 source is a biogas plant that's already running, the capture energy is partly accounted for. The overall carbon footprint of the storage is very low. Luna: That's impressive. Fifty kilowatt-hours per ton — compare that to direct air capture, which uses something like 2,000 kilowatt-hours per ton. This is orders of magnitude more efficient. Lucas: It's one reason why mineralization in building materials is such a hot area. The CO2 reacts exothermically in some cases, so you're not fighting thermodynamics as much. And the storage is permanent — it's not going to leak out like it might from a saline aquifer. Luna: Alright, so let's talk scale. Neustark has one plant in Switzerland processing 25,000 tons of aggregate per year. To make a dent in global cement emissions, they'd need thousands of such plants. What's the plan? Lucas: They're licensing the technology, not just building their own plants. They partner with demolition companies and recycling centers, install the CO2 injection equipment, and then sell the carbonated aggregate and the carbon credits. The capital cost per plant is relatively low — around a million euros — and the payback period is estimated at two to three years based on credit sales. Luna: So it's a franchise model for carbon removal. That could scale quickly if the carbon credit market holds up. But carbon credit prices are volatile. What happens if the price drops to $50 per ton? Lucas: Then the economics get tighter. But Neustark also has revenue from selling the aggregate itself, which provides a floor. And as carbon pricing increases — like Europe's Emissions Trading System, which is now above 80 euros per ton — the incentive for construction companies to use low-carbon materials grows. So it's not just voluntary credits; it's also regulation-driven demand. Luna: So the model is diversified: aggregate sales, carbon credits, and avoided carbon taxes. That's more resilient than a pure credit play. I wonder if we'll see similar plants popping up in the US, where demolition waste is abundant but carbon pricing is less advanced. Lucas: There are already companies exploring it. CarbonCure is in the US and Canada. And there's a startup in California called CarbonBuilt that's doing something related with concrete block. The US market is huge because the building stock is older and demolition is constant. But without a carbon price, the business case relies entirely on voluntary credits and green building certifications like LEED. Luna: So it's a race between technology scaling and policy. If carbon prices rise globally, this could become a mainstream process. If not, it might stay niche. Lucas: That's the bet. And Neustark is betting that the trend is towards higher carbon prices. They recently raised 70 million euros from investors including the European Investment Bank. So the smart money thinks this can work at scale. Luna: Seventy million euros — that's serious. It tells me that the investors believe in the economics, not just the climate impact. And that's what makes this a business story, not just a science story. Lucas: Exactly. And that's the thread we'll keep following: which industrial carbon removal technologies actually make money, and which ones stay in the lab.