Research project: ETH Zurich develops building elements from bacteria-bound sand
23.10.2026
Figure: Kai-Hsun Yeh/ETH Zürich
Researchers at ETH Zurich are combining biocementation with 3D printing and robotics to produce solid building elements from sand and bacteria. The process uses microorganisms that produce calcium carbonate, binding individual sand grains together. The first façade elements have already been produced.
At ETH Zurich's Department of Architecture, Karen Antorveza Paez is investigating a process in which bacteria act as a binding agent for mineral-based building materials. Unlike conventional cement production, the material is solidified without high kiln temperatures. Instead, the microorganisms form microscopic calcite crystals that interlock between the sand grains, creating a solid structure.
This process is known as microbially induced calcium carbonate precipitation (MICP), or biocementation. The principle is already known from soil stabilization and research into self-healing concrete. What is new is its combination with digital fabrication methods to produce individual architectural building elements.
Biocementation in 3D printing
For the first process, the researchers developed a printable mixture consisting of a water-based gel, sand and living bacteria. The gel contains natural substances including alginate and xanthan gum. This bio-ink can be shaped using a 3D printer.
The printed object is then immersed in a solution of urea and calcium chloride. The bacteria break down the urea using the enzyme urease. This produces carbonate ions, which react with calcium ions to form calcium carbonate. The resulting crystals bind the sand grains together and solidify the building element.
Depending on the required strength, this process takes between two and five days. During this time, the mineralization bath is replaced daily. The building element is then dried at room temperature, without the need for additional heating.
Using this method, the researchers have produced a free-standing façade element that could potentially be used as a sunshade or partition wall.
Robot-assisted fabrication without a mineralization bath
In a second approach, the researchers are using a robot-assisted spraying process. A robotic arm repeatedly applies sand, bacteria and the substances required for mineralization to a surface in successive layers. In this way, the structure gradually grows layer by layer.
The process is inspired by the natural formation of stromatolites, in which microorganisms produce mineral deposits over long periods of time. At the 2025 Venice Architecture Biennale, the process was demonstrated continuously over a period of six months.
According to the researchers, the method demonstrates the potential for automating biocementation. While 3D printing is primarily intended for producing individual building elements, the robot-assisted spraying process focuses on the fabrication of surfaces.
Further research needed on strength and environmental impact
However, considerable research is still required before the material can be used for load-bearing applications. According to Antorveza Paez, the material currently produced is more comparable to mortar than to concrete in terms of its properties. In particular, the relationships between particle size distribution, internal structure, bonding and long-term durability require further investigation.
The environmental impact of the process has also not yet been fully assessed. The microbial reaction produces ammonium as a by-product, which can cause environmental pollution if not disposed of properly. The researchers are therefore investigating ways to reduce these effects.
The results obtained so far demonstrate how biological mineralization processes can be combined with additive and automated manufacturing methods. Whether and to what extent biocementation can be used in the production of building elements in the future will depend, among other factors, on further improvements in material properties and environmental compatibility.
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