Using bacteria to bind loose sand grains into a solid, usable construction material, researchers at ETH Zurich have demonstrated a potential alternative to conventional cement.
The team, led by Karen Antorveza Paez, employed Sporosarcina pasteurii, a bacterium that can form calcium carbonate under the right conditions. This process binds sand particles together.
The motivation behind the project is the environmental cost of traditional cement, whose production requires high temperatures and large amounts of energy, making it a major source of carbon emissions.
While the principle of biocementation has been used before, for purposes such as stabilising soil or repairing cracks in concrete, the ETH Zurich project is distinct in its goal: to create a sand-based material that can serve as an independent architectural resource.
The team developed two fabrication methods. The first combines biocementation with 3D printing. A special "bio-ink" containing sand, water, the bacteria and a mix of chemicals is printed into a desired shape. The object is then immersed in a bath of urea and calcium chloride for three days, during which the bacteria trigger crystallisation that binds the sand. A subsequent two-day drying period at room temperature completes the process, yielding a solid structure. Antorveza Paez compared the overall process to baking a cake, calling the raw printed object the dough and the bacteria the oven that hardens it without any heat.
The second method uses a robotic arm to spray a mix of sand and bacteria onto a surface, building structures layer by layer. Its key advantage is that it can be fully automated; the team ran the system continuously for six months.
The two approaches have different applications, with 3D printing suited to complex architectural elements and robotic spraying designed for surfaces.
The technology still has limitations. One of the most concerning is ammonium, a byproduct of the mineralization bath in the 3D printing method. It is very toxic, and researchers need to find ways to neutralise it before scaling up the technology. The material's strength is also an open question: for now, it could replace mortar, which binds bricks together, but it is still not quite as strong as concrete, which can support floors, columns and foundations. The team is also studying how the size of sand grains affects the final product's properties.
Analysis
Why This Matters
- Construction accounts for a significant share of global carbon emissions, largely due to cement production, which requires extremely high kiln temperatures. This microbial approach operates at room temperature, offering a potential pathway to drastically lower the carbon footprint of building materials.
- The successful six-month continuous run of the automated robotic spraying method demonstrates the potential for the process to be scaled for industrial use without constant human oversight.
- The ability to turn a raw material like sand into solid architectural elements directly, rather than just binding existing materials, opens new possibilities for construction in regions with limited access to concrete supply chains.
Background
Cement manufacturing is a major industrial source of greenhouse gases, estimated to produce roughly 8% of global carbon dioxide emissions. The process of biocementation, also known as microbially induced carbonate precipitation (MICP), is a naturally occurring process that has been artificially harnessed for decades. Previous applications have focused on repairing cracks in concrete structures, stabilising soil against erosion, and consolidating loose ground. The ETH Zurich project represents a shift away from using bacteria as a repair tool and toward using it as the primary fabrication engine for a new class of material.
What to Watch
- A solution for the toxic ammonium byproduct: the researchers must find an economically viable way to neutralise or recycle the ammonium generated during the 3D printing process before the technology can be considered environmentally benign and scaled.
- A milestone in compressive strength: if the team can achieve a strength comparable to standard structural concrete, the material could begin to replace cement in non-structural and eventually structural applications.
- A move toward prototype architectural projects: the next step for the ETH Zurich group will likely be a demonstration structure or a partnership with an architecture firm to test the material outside the laboratory.
Checked
12 claims in this story checked against 1 source: 12 supported.
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- SupportedBacteria bind sand into building material.New Atlas: Technology-Innovation-Outdoor News: “if its grains could stick together, it could become a solid building material”
- SupportedThe ETH Zurich team uses microbial cementation to turn sand into durable building material.New Atlas: Technology-Innovation-Outdoor News: “the result is a solid, durable structure”
- SupportedThe researchers demonstrated a potential alternative to conventional cement.New Atlas: Technology-Innovation-Outdoor News: “it could become a solid building material, offering an alternative to conventional cement.”
- SupportedThe team was led by Karen Antorveza Paez.New Atlas: Technology-Innovation-Outdoor News: “Led by Karen Antorveza Paez, the research group found two ways to make this work.”
- SupportedSporosarcina pasteurii can form calcium carbonate that binds sand particles together.New Atlas: Technology-Innovation-Outdoor News: “Under the right conditions, it can grow between sand grains and bind them together by forming calcium carbonate”
- SupportedTraditional cement production requires high temperatures and substantial energy, making it a major source of carbon emissions.New Atlas: Technology-Innovation-Outdoor News: “its production requires very high temperatures and large amounts of energy, making it a major source of CO2 emissions.”
- SupportedBiocementation has previously been used to stabilise soil and repair cracks in concrete, while the ETH Zurich project aims to make sand an architectural material on its own.New Atlas: Technology-Innovation-Outdoor News: “We’ve previously seen it used to stabilize soil for growing crops and to help repair cracks in concrete. What’s different about the ETH Zurich project is the ultimate goal: the scientists are using biocementation not to just improve existing materials, but rather to turn sand into an architectural material on its own.”
- SupportedThe 3D-printed object is immersed in a urea and calcium chloride bath for three days, then dried at room temperature for two days.New Atlas: Technology-Innovation-Outdoor News: “it’s immersed in a bath with urea and calcium chloride for three days. ... the object is dried at room temperature for two days”
- SupportedAntorveza Paez compared the process to baking a cake, describing the printed material as dough and bacteria as the oven that hardens it without heat.New Atlas: Technology-Innovation-Outdoor News: “Antorveza Paez compares this process to baking a cake: “You’ve got the dough, which is still very malleable and delicate. Only the oven can turn it into something solid.” In this case, bacteria act as an oven and hardens the material, but does it without any heat.”
- SupportedThe second method uses a robotic arm to spray sand and bacteria onto a surface, building structures layer by layer; it can be fully automated.New Atlas: Technology-Innovation-Outdoor News: “The second method uses a robotic arm to spray the mix of sand and bacteria onto the surface. The desired object is built gradually, layer by layer, as calcium carbonate gets formed. ... its main advantage is that it can be fully automated.”
- SupportedThe robotic system ran continuously for six months.New Atlas: Technology-Innovation-Outdoor News: “This system ran continuously for six months, showing its ability to operate without constant human supervision.”
- SupportedAmmonium, a by-product of the 3D-printing mineralization bath, is very toxic and must be neutralised before the technology is scaled up.New Atlas: Technology-Innovation-Outdoor News: “One of the most concerning ones is ammonium, a by-product of the mineralization bath in the 3D printing method. It’s very toxic, so researchers need to find ways to neutralize it before scaling up the technology.”
