Bacteria are helping print sand into new building materials
MICP
A process where bacteria help form calcium carbonate between grains.
Sporosarcina pasteurii
The bacterium used in these experiments.
stromatolites
Layered rocks shaped by microbial mineral growth.
What happened
Researchers at ETH Zurich are testing a building material that uses bacteria to bind loose sand. The project was led by Karen Antorveza Paez during her doctoral research. It combines microbiology with 3D printing and robotic fabrication. Three studies describe two ways to make architectural elements. One prints a shape first. The other builds a surface with repeated robotic spraying.
How the sand becomes solid
The key process is called microbiologically induced calcium carbonate precipitation, or MICP. It is also called biocementation. The team uses Sporosarcina pasteurii, a bacterium studied for years in soil stabilization and self-healing concrete research.
For 3D printing, the researchers make a bio-ink. It contains a water-based gel, alginate, xanthan, sand, and live bacteria. They print the desired form. Then they place it in a bath containing urea and calcium chloride. An enzyme in the bacteria breaks down the urea. This releases carbonate ions. The carbonate reacts with calcium to form calcium carbonate. That is the same mineral found in limestone, chalk, and mussel shells. Tiny crystals grow between the sand grains. The crystals interlock and hold the grains together.
The piece needs two to five days to harden. The team refreshes the mineralization bath each day. The piece then dries. After drying, the bacteria are no longer active.
Why it matters
Cement production heats rocks above 1,000°C. It is also a major source of carbon dioxide emissions from construction. The bacterial process hardens the printed form at room temperature. It needs no heat source for that step. This could lower energy use. It does not prove that the whole process is sustainable.
The reaction produces ammonium as a byproduct. Ammonium can damage the environment. Any future design must include a way to manage or dispose of it.
What has been demonstrated
The researchers made a facade element. It could provide shade or divide a space. They also tested robotic biocementation spraying. A robotic arm applies bacteria, mineralization ingredients, and sand in sequence. It builds the material layer by layer.
The spraying idea was inspired by stromatolites. These are layered rock formations shaped by microbial mineral growth. At the 2025 Venice Architecture Biennale, the system ran for six months. The demonstration showed that the biocementation process can be automated.
The two methods are not equally mature. Printing focuses on making architectural elements. Spraying focuses more on surfaces. The spraying method still needs more study of its mechanical properties.
What remains uncertain
The researchers compare current biocementation with mortar, not concrete. It is not ready to replace load-bearing concrete. Scientists still need to control grain sizes, material proportions, strength, and long-term stability. Those details will decide whether the method can become a practical building system.
What to watch next
The next steps include testing durability, scaling up production, and measuring the full environmental impact. That assessment must include the mineralization bath and ammonium waste. The central question is no longer whether bacteria can harden sand. It is whether engineers can control the result well enough for safe, durable architectural use.
Sources: ETH Zurich research summary, robotic spraying study.
Bacteria can help turn loose sand into building pieces
📰 Full story: Bacteria are helping print sand into new building materials
Tiny living cells can join sand grains. The method is promising, but still experimental.
MICP
A method that uses bacteria to make calcium carbonate.
Sporosarcina pasteurii
The bacterium used in the tests.
ammonium
A chemical byproduct that can harm nature.
💡 The gist
- Bacteria can make stone between loose sand grains.
- A printer or robot can shape the material.
- It is not ready for load-bearing buildings.
Karen Antorveza Paez, a researcher at ETH Zurich, studies this material. ETH Zurich is a Swiss university. Her work joins biology with digital building tools.
The method is called MICP. It is also called biocementation. MICP uses bacteria to form calcium carbonate. Calcium carbonate is the mineral in limestone.
The team uses Sporosarcina pasteurii, a bacterium used in the tests. They mix sand, live bacteria, and a soft gel. A 3D printer makes the chosen shape. The piece then enters a bath with urea and calcium chloride.
The bacteria break down the urea. That reaction helps create calcium carbonate. Small crystals form between sand grains. The crystals lock the grains together.
The piece hardens at room temperature. It takes two to five days. The team replaces its special bath each day. The piece dries afterward. The bacteria stop working after drying.
Cement making heats rocks above 1,000°C. It is a major construction source of carbon dioxide. Biocement avoids that heating step. Lower energy use does not prove full sustainability.
The reaction also makes ammonium. Ammonium can harm nature. Researchers must find safe ways to handle it.
The team tested a second method. A robotic arm sprays bacteria, minerals, and sand in layers. The idea was shown at the 2025 Venice Architecture Biennale. The system ran for six months.
The team made a facade piece. It could block sunlight or divide rooms. Researchers compare the material with mortar, not concrete. It is not ready for load-bearing buildings. Strength and long-term stability need more research.
Next, scientists will study durability, larger production, and environmental effects. They must count waste from the mineral bath, too. The key challenge is controlling the material reliably.
Tiny helpers join loose sand
📰 Full story: Bacteria are helping print sand into new building materials
Tiny bacteria can help sand grains stay together.
ETH Zurich
A university in Switzerland.
3D printer
A machine that makes shapes.
ammonium
A leftover chemical that can hurt nature.
ETH Zurich is a university in Switzerland. Karen Antorveza Paez is a researcher there. She studies tiny helpers called bacteria.
Sand has many tiny grains. The grains can fall apart. The team mixes sand, bacteria, and soft gel. A 3D printer gives the mix a shape. The shape goes into special water.
The bacteria make tiny stones. The stones grow between sand grains. They hold the grains together. The shape needs two to five days. Then it dries and becomes hard. The bacteria stop working after drying.
Normal cement uses very hot rocks. The heat can make much carbon dioxide. This process uses no heat to harden.
A robot can also spray the layers. It worked for six months at a Venice show. The material could block sunlight or divide rooms.
It cannot yet hold up big buildings. The process also makes ammonium. Ammonium can hurt nature. Researchers are studying safe cleanup.