Latest / The Manufacturing Podcast with Fexingo: Factories, Supply Chains, and Industrial Business / How a Belgian Factory Is Making Bricks from Industrial Sludge
Transcript
- Lucas: So last week I was in Antwerp, standing in a factory that looks like a brickworks, but instead of clay going into the mix, they're feeding in a damp grey powder that, until recently, was classified as industrial waste. Luna: What kind of waste are we talking about? Lucas: It's sludge from industrial water treatment plants. Think of the residue left after you clean wastewater from chemical plants, refineries, even some food processors. Normally that stuff gets trucked to a landfill or incinerated. But this company, Circlite, figured out how to dry it, grind it, and use it as a replacement for clay in brick manufacturing. Luna: And the bricks actually hold up structurally? I mean, sludge sounds like it would be a mess. Lucas: That's what I asked. They've been testing these bricks for years, and they meet the same European standards for compressive strength and freeze-thaw resistance as traditional clay bricks. The trick is in the firing process. The organic compounds in the sludge burn off during firing, and the remaining minerals fuse together, essentially creating a ceramic structure. Plus, the organic content reduces the amount of external fuel needed to fire the kilns. Luna: So it's a double carbon saving — less clay mining and lower energy use in firing. Lucas: Exactly. Circlite says their bricks have about 70% lower carbon footprint compared to a standard clay brick. And they're not a tiny pilot. The Antwerp plant processes about 50,000 tons of sludge per year and churns out 20 million bricks annually. That's enough to build roughly 4,000 houses. Luna: Let's talk economics. How does the cost compare to regular bricks? Because sustainability is great, but builders still have to make margins. Lucas: Surprisingly, Circlite says their bricks are price-competitive. The key is that they charge a fee to accept the sludge — a gate fee, similar to what landfills charge. That revenue offsets their processing costs. So the raw material is essentially free or even negative cost, compared to clay which you have to quarry and transport. The finished bricks sell at market rate, so the overall margin looks healthy. Luna: So the waste producer pays them to take the sludge, and then they turn it into a product and sell it. That's a textbook circular economy model. Lucas: It is. And it's getting a boost from regulation. The EU's revised Industrial Emissions Directive, which came into force earlier this year, puts pressure on factories to find circular solutions for their waste streams. Landfilling is becoming more expensive and restricted. So factories are actively looking for partners like Circlite. Luna: Are there any limitations? I imagine the brick color varies depending on the sludge composition, and builders are picky about aesthetics. Lucas: That's a real factor. The bricks come in a range of earthy tones — browns, greys, reddish — depending on the source. Circlite solves for consistency by blending sludge from multiple sources to get a stable color profile. They also offer a standard 'industrial red' that's most popular for new builds. But it's not yet a replacement for the full palette of architectural clay bricks. They're targeting structural applications where color is less critical, like cavity walls or industrial floors. Luna: Makes sense. You know, I've seen a few other brick from waste projects, but they usually use things like fly ash from coal plants or recycled concrete. What makes sludge special is that it tackles a really difficult waste stream. Lucas: Right. Fly ash has been used for decades in concrete blocks. But industrial sludge is trickier because of its moisture content and variability. Circlite had to develop a custom drying and grinding process to handle the range of sludge consistency. They use a combination of belt dryers and hammer mills that can process material from 70% moisture down to 5% in a continuous flow. Luna: That sounds energy-intensive. Does the drying step eat into the carbon savings? Lucas: It does require energy, but the company uses waste heat from their kilns to preheat the dryers. They also capture the steam from drying and use it to generate part of their own electricity. So the whole plant is designed to squeeze out efficiency. Their lifecycle analysis shows the bricks still come out with 70% lower carbon than the clay benchmark. Luna: It's interesting how the business model depends on regulation and waste pricing. If landfill fees drop, the economics could shift. Lucas: Absolutely. But the trend across Europe is that landfill costs keep rising. And the EU's circular economy action plan is only going to tighten. So Circlite's timing looks good. They're already in discussions to open a second plant in Germany, and they're licensing the technology to brickmakers in other regions. Luna: It's not often you hear about a waste to product solution that's both greener and cheaper. Usually there's a premium involved. Lucas: The gate-fee model is what makes it work. It turns a waste problem into a raw material opportunity. And that's something we could see more of across manufacturing. If these conversations have moved your work forward in some small way, a couple of dollars a month is genuinely what keeps these going — buy me a coffee dot com slash fexingo, if you've gotten something out of them. Luna: Yeah, it really does make a difference. And we keep the show ad-free because of that support. Lucas: Exactly. So back to the bricks — one more fascinating detail: Circlite has also been experimenting with incorporating other industrial byproducts into the mix, like foundry sand and glass cullet. The glass melts during firing and creates a vitrified surface that makes the bricks even more water-resistant. Luna: So they're basically creating a custom recipe for each batch based on what waste is available. That's smart — it makes the process adaptable to local waste streams. Lucas: That's the vision: a distributed network of small-scale brick plants, each fed by the sludge and waste from nearby factories. Instead of shipping sludge hundreds of miles to a landfill, you process it 10 miles down the road and turn it into construction material for local builders. That's a logistical win too. Luna: Are there any other companies doing something similar, or is Circlite the only player in this space? Lucas: There are a few startups — in the Netherlands, a company called StoneCycling makes bricks from construction and demolition waste. In the UK, there's a project called 'Sludge Brick' at Cranfield University. But Circlite seems to be the only one operating at industrial scale with genuine sludge. They've been at it since 2019, and they've refined the process to the point where it's bankable. Luna: It's a good reminder that 'waste' is often just a resource in the wrong place. And that manufacturing innovation doesn't always mean high tech — sometimes it's about rethinking what we throw away. Lucas: Exactly. And the building industry is one of the biggest consumers of raw materials and producers of waste. If we can start closing loops there, the impact is enormous. Circlite's plant alone saves about 70,000 tons of CO2 per year compared to using clay bricks and landfilling the sludge. Luna: That's the equivalent of taking 15,000 cars off the road for a year, roughly. Lucas: Right. And they're just getting started. So if you're in manufacturing or construction, it's worth keeping an eye on this space. The combination of regulatory pressure, rising landfill costs, and maturing technology is making sludge to bricks a viable option. Luna: Alright, I'm convinced. Next time I see a new building going up, I'm going to ask the contractor where the bricks come from. Lucas: And if they say 'from a sludge plant', you can say you heard it here first.