In the last article on the GovDesignHub , we sat down with Max Latour, Founder and Computational Designer at Urban Reef—a 3D printing company that specializes in sustainable, bioreceptive structures that merge infrastructure with ecology—to learn more about the Maaskracht project, the role their 3D printed clay reefs play in this project, and how lessons from this project could be applied to future sustainable infrastructure developments.
This initiative comes at a critical time. Across Europe, stricter water quality regulations and growing climate pressures are prompting agencies to seek new ways to protect waterways while restoring biodiversity.
Urban Reef’s involvement in the Maaskracht project highlights how innovative partners can bring fresh ideas to longstanding challenges – introducing sustainable materials, circular processes, and additive manufacturing techniques that reduce ecological impact while enhancing resilience.
In the second part of our discussion, Max delves into the sustainable materials and additive manufacturing processes behind the company’s clay reefs, exploring the challenges of working with clay compared to other printable materials, and discussing how 3D printing can play a transformative role in ecological restoration over the next decade.
GDH: What types of sustainable materials are used to print these reefs?
Max Latour: The reefs we installed there are honestly not as sustainable as we would like them to be. They were printed in ceramics, which is often seen as a sustainable material because it’s made from clay, but in reality, it isn’t – mainly because of the high-energy firing process.
Right now, we’re working on two areas to improve this. First, we’re looking for a better clay source. The clay we used originated from a pit in Germany, meaning it was all virgin material. However, in the Netherlands, rivers are regularly dredged to keep them clear for navigation, and the dredged material often contains clay. We’re now investigating how to use that dredged clay instead, which would make the process more circular.
The second step is to reduce or eliminate the firing process. To achieve this, we’re researching alternative materials that can harden at room temperature, utilizing binding materials—such as geopolymers and biopolymers—in place of firing. This would dramatically lower the ecological footprint.
In fact, that more sustainable dredged clay is already being put to use; in partnership with Blauwe Bagger, which extracts the material, we’re collaborating with a client in Rotterdam to produce the same reef structures originally designed for the Maaskracht project.
GDH: Can you walk us through the additive manufacturing process for these clay reefs—from design to installation?
Max Latour: The first step in this project was our initial meeting with the Maaskracht team, where we defined the specific function the structures needed to serve. From there, we moved into the design phase. At Urban Reef, we already have a set of design processes we’ve developed, but for each project, we test and adapt them to see what fits best.
“Now, we’re looking into alternative materials with lower CO₂ emissions. Geopolymers, for example, behave more like concrete in terms of strength and durability, but with a significantly reduced carbon footprint.” –Max Latour
These processes are based on algorithms that mimic natural morphogenetic processes, essentially how shapes and geometries form in nature. We simulate these on the computer and develop them into design tools that guide our work.
Many of these tools were already in place, but we refine them iteratively: we define the algorithm, conduct some test prints, observe how the material behaves, and then update the algorithm until the results become more stable and reproducible.
For this project, we selected a specific design tool and then went through rounds of printing and iteration, as it’s never a purely linear process. We used a relatively small printer, a WASP 4100 clay printer, which is also quite accessible in terms of cost.
One challenge with printing is that the objects usually have one flat side. To avoid that, we printed the design in two orientations—one from the bottom up, the other from the top down—and then joined them together. The result was a piece that resembled a natural rock in the rock armor, without flat surfaces.
Finally, the installation was carried out using the same crane that had placed the rock armor, so our clay reefs were installed alongside the rocks themselves.
GDH: How does 3D printing with clay differ from other large-scale additive manufacturing methods in terms of sustainability and performance?
Max Latour: In terms of sustainability, PC concrete—epoxy adhesive specifically formulated for concrete anchoring and repair applications—is among the worst material you can use. And for 3D printing, it’s even worse than regular concrete, because you have to change its characteristics to make it printable. Ceramics are better, but not ideal either, as they require firing, which consumes a significant amount of energy.
When it comes to printing itself, every material behaves differently. For example, plastic cools and hardens within seconds, and printable concrete uses accelerants that set it within a minute.
“…our larger ambition is global – we want to help establish a new paradigm for how people view nature in urban environments, and we see ourselves playing an active role in that shift.” –Max Latour
Clay, on the other hand, stays moist and soft for up to two weeks. That makes it much harder to work with – you have to design specifically for clay as a viscous material. It also limits the scale, since you can only print to about 600 millimeters in height before it collapses.
Even if you adjust the nozzle or other settings, the material is too soft to go higher. The printers themselves also have to be designed differently. Clay printing requires higher viscosity and different mechanics than plastic or concrete printers.
Now, we’re looking into alternative materials with lower CO₂ emissions. Geopolymers, for example, behave more like concrete in terms of strength and durability, but with a significantly reduced carbon footprint.
GDH: How do you envision the role of additive manufacturing evolving in ecological restoration over the next decade? Do you anticipate scaling this approach to other waterways or coastlines beyond the Netherlands?
Max Latour: Yes, we’re always open to projects abroad, but right now our primary focus is on the Netherlands, because we want to monitor the projects closely. The concept itself is quite generic – creating diversity by building a 3D printed clay reef that allows the ecosystem to develop on its own. However, at the same time, each project is highly site-specific, as once the ecosystem takes hold, it truly becomes an integral part of that place.
For us, it’s important to be able to visit and see what’s happening firsthand. So, at this stage of the company, we’re trying to keep projects local. That said, our larger ambition is global – we want to help establish a new paradigm for how people view nature in urban environments, and we see ourselves playing an active role in that shift.
