ResearchETH Zurich researcher prints bacteria-bound mineral structures as a cement alternative
Karen Antorveza Paez, who recently finished her doctorate at ETH Zurich's architecture department, combines bacteria with digital fabrication to make limestone-like building elements without cement. One route is 3D printing a bio ink, the other is robotic spraying. For now the material suits non-load-bearing parts such as façades and partition walls.
Key facts- Cement causes roughly 7% of global carbon emissions
- Bio ink: hydrogel, alginate, xanthan, sand and live Sporosarcina pasteurii
- Curing takes two to five days in daily fresh baths
- Output is mortar-like, for non-load-bearing elements
Context Biocementation uses bacteria to turn loose sand into a solid by growing interlocking calcite (calcium carbonate) crystals between the grains.
How does the printed biocement process work?
The bio ink combines hydrogel, alginate, xanthan, sand and live Sporosarcina pasteurii bacteria. It is extruded into a delicate freeform structure, comparable to a green part. The structure is then placed in a bath of urea and calcium chloride. The bacteria use the enzyme urease to break down the urea, producing carbonate ions that react with calcium chloride to form calcium carbonate, or limestone.
How long does it take, and what is it good for?
Depending on the strength needed, the process takes two to five days, with a fresh bath each day. The part is then dried. The researcher describes the result as closer to mortar than concrete, so it currently suits non-load-bearing elements such as façades or partition walls. Further work on property control is needed.
What is the robotic spraying route?
A robotic arm alternately sprays bacteria, mineralisation ingredients and sand onto a surface, inspired by stromatolite rock layers. It offers less freeform design potential than printing but could serve for making surfaces.
What it means
This is early-stage research, not a product. For manufacturers and construction firms in the EU, the relevant points are the limits stated so far: mortar-like properties, no load-bearing use, and a two to five day curing cycle with daily bath changes. No cost, scale or certification data is given, so a business case cannot yet be built. It is worth watching as a low-carbon route for façade and partition elements.
Frequently asked questions
Why look for alternatives to cement?
Cement accounts for roughly 7% of global carbon emissions, driven by clinker production and the calcination of limestone.
Can the bacteria-based material carry loads?
Not yet. It is closer to mortar than concrete and is suited to non-load-bearing elements such as façades or partition walls.
How long does the printed part take to harden?
Two to five days, depending on required strength, with the structure placed in a fresh urea and calcium chloride bath each day.