Cement is one of the most carbon-intensive things the construction industry makes, largely because it has to be fired at temperatures above 1,000°C. A researcher at ETH Zurich has spent her doctorate asking a different question: what if you didn't fire anything, and let bacteria do the binding instead?
Karen Antorveza Paez, who has just completed her doctorate in the university's Department of Architecture, has shown that loose sand can be set into solid architectural elements at room temperature. The work was described by ETH Zurich on October 14, 2026, and rests on three studies published in 2026.
How the bacteria "glue" sand
The method is called microbiologically induced calcite precipitation, or biocementation. The bacteria, Sporosarcina pasteurii, have been studied for years, including for stabilising loose soil and for "self-healing" concrete. When they are mixed with sand and fed the right chemicals, they produce calcium carbonate, the mineral in chalk and mussel shells. Microscopic crystals grow between the grains and interlock.
Antorveza Paez describes it this way: "We're using bacteria to produce a sort of mineral glue." The glue is not a conventional adhesive. It is a network of crystals that mechanically holds the grains together.
What is new is control. She combined biocementation with digital fabrication, so the process can be used to make architectural elements on purpose rather than as an additive to existing materials.
Two ways to make it
The first method is 3D biocement printing. The team made a "bio-ink" from a water-based gel of alginate and xanthan, plus sand and live bacteria. It prints like a normal paste. The printed object is then placed in a bath of urea and calcium chloride, where the bacteria break down the urea and the limestone forms. The process takes two to five days depending on the strength needed, with a fresh bath each day. Once it dries, the bacteria are no longer active.
She compares it to baking: the printed form is soft dough, and the bacteria act as the oven, setting it slowly with no heat source. One result was a facade element that could serve as sun protection or a partition wall.
The second method is robotic spraying. A robotic arm repeatedly applies bacteria, the mineral-forming chemicals and sand to a surface, building it up layer by layer, inspired by stromatolites, the layered rock formations microorganisms create in nature. The team ran it continuously for six months at the 2025 Architecture Biennale in Venice. Printing suits elements and spraying suits surfaces, and the two are at different stages. The spray process still needs significantly more research into its mechanical properties.
What it can't do yet
The researcher is direct about limits. At present, biocementation is closer to mortar than concrete. Concrete's recipe has been refined for over a century, while the equivalent work for biocement is only starting. She puts it this way: "The big question is no longer whether biocement works, but rather how well its properties can be managed." Load-bearing structures, in her words, are still a long way off.
There is also an environmental catch. The reaction creates ammonium as a by-product, which is very damaging to the environment. If disposal is not designed in, she says, biocement won't be very sustainable. A third study on the environmental impact is under way.
A note on other "sand" research
Several teams are working on sand as a building material, but they are not the same thing. Researchers at the Norwegian University of Science and Technology and the University of Tokyo made "botanical sand concrete" from desert sand and wood-based additives, pressed under heat, which is not heat-free. A team at the University of Sharjah reported desert-sand bricks using alkali-activated binders. These approaches address sand supply and cement use in different ways, and the headline claim of no heat applies only to the bacterial method.
What happens next
This is early-stage research. Nothing in the reporting suggests commercial products or building-code approval yet. The next tests are about strength, durability and how to handle the ammonium waste. If those are solved, biocement might first find a place in non-structural uses like facades, partitions and surfaces, which is where the researcher's own examples sit.
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