ZURICH, October 18, 2026 — Researchers at ETH Zurich have demonstrated a method to produce solid architectural elements by using bacteria to bind sand, bypassing the extreme heat required for traditional cement production. This innovation offers a potential shift for the construction industry, which currently relies on energy-intensive processes as a primary source of carbon emissions.
The Environmental Cost of Traditional Construction
The global construction industry faces significant pressure to reduce its environmental footprint, primarily due to the production of traditional cement. According to reports from ETH Zurich, manufacturing conventional cement requires heating rocks to temperatures exceeding 1,000°C. This energy-intensive process makes cement production one of the largest sources of CO2 emissions within the global building sector.
In contrast, the new biocementation method allows structures to harden at room temperature. By eliminating the need for external heat sources, this approach addresses the high energy demands that have long characterized the industry. As researchers look for ways to transition toward more sustainable practices, the ability to create building materials without massive thermal input represents a significant change in manufacturing logic.
How Biocementation Mimics Natural Mineral Formation
The process developed by researchers, including Karen Antorveza Paez, relies on a technique known as microbiologically induced calcite precipitation, or MICP. This method uses the bacterium *Sporosarcina pasteurii* to facilitate the formation of calcium carbonate, the same mineral found in natural limestone. This is not the first time this bacterium has been studied; it has previously been investigated for its ability to stabilize loose soil and help concrete cracks seal themselves.
The transformation from loose sand to solid material occurs through a specific chemical chain reaction. When the bacteria are combined with sand, they break down urea using the enzyme urease. This reaction releases carbonate ions, which then react with calcium chloride to create microscopic calcite crystals. These crystals grow between the grains of sand and interlock, effectively acting as a mineral glue that holds the particles together in a solid structure.
Integrating 3D Printing and Robotic Spraying
To move beyond laboratory experiments, researchers have combined biocementation with digital manufacturing. One method involves 3D biocement printing, where a bio-ink is created using water, alginate, xanthan, sand, and live bacteria. Once the object is printed into the desired shape, it is immersed in a solution of urea and calcium chloride to trigger the mineralization process.
A second manufacturing method utilizes robotic spraying. In this approach, a robotic arm repeatedly applies the bacteria, sand, and mineral-forming substances to a surface, building the structure layer by layer. This process draws inspiration from stromatolites, which are layered sedimentary rock formations created when microorganisms deposit minerals over long periods. At the 2025 Biennale Architettura in Venice, this robotic process was demonstrated continuously for six days, showcasing the potential for automated construction.
Structural Integrity and Production Timelines
The strength and durability of these biogenic materials depend on the duration of the mineralization process. According to the research, printed structures typically require two to five days to complete, depending on the specific strength requirements of the architectural component. During this time, the object is placed in a fresh mineralization bath each day to replenish the substances the bacteria need to continue forming calcium carbonate.
Once the process is complete and the structure has dried, the bacteria are no longer active, leaving behind a solid mineral object. Antorveza Paez described the process as similar to baking, where a malleable dough is transformed into a solid through a controlled reaction. While traditional cement relies on heat to achieve its final state, this method relies on the mechanical interlocking of calcite crystals to provide structural integrity.
Future Potential for Sustainable Construction
The integration of biological processes into digital manufacturing opens a new design space for building technology. While research into living building materials has been ongoing for decades—including early work on mycelium-based insulation and self-healing concrete projects like the UK’s Resilient Materials 4 Life consortium—the focus at ETH Zurich is on using biocementation as a primary structural material.
The ability to engineer these materials allows for the potential of self-organizing and self-healing structures. Programs such as the United States Department of Defense’s Engineered Living Materials project have previously sought to develop tools for creating materials that can reproduce or repair themselves. By controlling these biological processes through 3D printing and robotics, researchers are moving toward a future where building materials are not just passive components, but active systems that can be manufactured with significantly lower energy inputs than those required by current industry standards.
Structural Integrity Through Interlocking Calcite Crystals
The structural strength of these biogenic materials is derived from the chemical transformation facilitated by the bacterium Sporosarcina pasteurii. As the bacteria break down urea using the enzyme urease, they release carbonate ions as a primary reaction product, alongside ammonium. These carbonate ions subsequently react with calcium chloride to precipitate calcium carbonate, the same mineral composition found in natural limestone, mussel shells, and chalk.
Rather than relying on a traditional adhesive, the material achieves its durability through the physical arrangement of these mineral deposits. Microscopic calcite crystals develop directly between the individual grains of sand. As these crystals grow, they interlock with one another, creating a mineral network that mechanically binds the sand particles into a solid, cohesive structure. According to Karen Antorveza Paez, this mechanism functions as a form of “mineral glue,” where the interlinked crystals act as the primary force holding the architectural element together.
This process represents a departure from conventional manufacturing, as the structural integrity is not a result of thermal bonding or heat-induced curing. Instead, the strength of the final object is determined by the duration of the mineralization process and the consistent replenishment of the necessary chemical precursors. By controlling the growth of these interlocking crystals, researchers can produce solid architectural elements that maintain their form after the drying process is complete and the bacteria have become inactive.
Sources
- Scientists use bacteria and 3D printing to turn sand into solid building materials without the extreme heat required to make cement
- Living building material
- Using Bacteria to Create Biocement Materials
Photo: Sufyan / Unsplash (Unsplash License)
