ETH Zurich scientists use bacteria to bind sand together for construction

An ETH Zurich scientist has proven that micro organism and digital manufacturing will also be used to construct free-form architectural components.

The method is seen as a promising, much less energy-intensive various to cement. Beforehand, it has primarily been used to stabilise soils, moulded tiles, and in analysis.

The analysis means that residing micro organism can bond sand and different unfastened grains collectively right into a strong materials by forming calcium carbonate, the mineral that makes up limestone.

The method appears partly like 3D printing (see video under).

Decreasing the warmth

Cement manufacturing is without doubt one of the largest sources of CO2 emissions within the development business. On the Division of Structure, Karen Antorveza Paez, who has simply accomplished her doctorate at ETH Zurich, is researching another that works in a very totally different approach: as a substitute of firing rocks at over 1,000°C, she is getting micro organism to bond grains of sand collectively into strong architectural components.

“We’re utilizing micro organism to provide a kind of mineral glue,” explains Antorveza Paez.

When sure varieties of micro organism are mixed with sand or different strong grains, they be part of the particles collectively right into a strong construction product of interlocking, microscopic calcite crystals.

The method is named microbiologically induced calcite precipitation (MICP), or just biocementation. It’s nothing new: the micro organism used for this, Sporosarcina pasteurii, have been beneath analysis for a few years, reminiscent of for stabilising unfastened subsoil.

They’ve additionally been utilized in concrete analysis for “self-healing” concrete, the place the introduction of bacterial spores causes cracks to seal over on their very own.

Antorveza Paez’s innovation is how the method is managed: not as an addition to present constructing supplies, however as an architectural materials in its personal proper. To realize this, she mixed two analysis fields that had till then been largely separate: biocementation and digital manufacturing.

Whereas it has lengthy been identified that micro organism can bond sand collectively into strong objects beneath sure situations, Antorveza Paez explains that, “What was lacking had been manufacturing processes whereby these organic processes might be managed as required and used to make architectural components”.

Two methods of constructing biogenic constructing supplies

In the middle of writing her doctoral thesis, three scientific research had been performed that describe two totally different manufacturing strategies.

For the primary methodology, 3D biocement printing, the staff developed a “bio-ink” product of a gel based mostly on water and the pure substances alginate and xanthan, in addition to sand and dwell micro organism.

As with a standard 3D printing paste, the bio-ink might be printed right into a given desired construction. The printed object is then immersed in a shower containing urea and calcium chloride.

That is the place the micro organism begin their work by breaking down the urea with an enzyme known as urease. This response releases carbonate ions and, as a by-product, ammonium.

The carbonate and calcium chloride within the resolution bond collectively to kind calcium carbonate, also called limestone – the identical mineral that makes up mussel shells and chalk.

The limestone kinds wherever the micro organism are situated throughout the printed object. Microscopic crystals kind between the grains of sand and “interlock” with one another.

That is what provides the method its gluing property: moderately than being glue within the conventional sense, it’s made up of interlinked mineral crystals that mechanically maintain the grains collectively.

‘Like baking a cake’

All the course of takes two to 5 days, relying on the specified power of the architectural element. This entails offering a recent mineralisation tub each day, in order that the micro organism don’t deplete the substances required to kind the limestone.

The thing is then left to dry. As soon as that is executed, the method is full. The construction has turned to strong mineral and the micro organism are not lively.

Antorveza Paez says, “It’s a bit like baking a cake. You’ve obtained the dough, which continues to be very malleable and delicate. Solely the oven can flip it into one thing strong.”

In her course of, the micro organism play the function of the oven: they slowly set the printed construction till it’s strong, bonded and dry at room temperature. No warmth sources are used.

This course of has been used to create a facade ingredient, amongst different issues. It may be used to supply safety from the solar or as a partition wall, for instance.

Absolutely digital manufacturing

A second method to making use of biocement for architectural functions is robotic spraying. On this method, the researchers eliminated the intermediate stage of the immersion tub.

A robotic arm applies micro organism, the mineralisation substances for limestone formation and sand to a floor repeatedly and one after the opposite, constructing it up in top layer by layer.

This course of is impressed by stromatolites, layered sedimentary rock formations that happen in nature when microorganisms deposit minerals over lengthy intervals of time.

On the 2025 Biennale Architettura in Venice, the method was left working uninterrupted for six months, letting guests see the outcomes for themselves.

“Now we have confirmed that your entire means of biocementation might be automated,” says Antorveza Paez.

The 2 processes are complementary: “The printing is geared extra in direction of architectural components, whereas the spray course of is extra designed for surfaces”, explains Antorveza Paez.

The place the main focus of the printing course of was on supplies science – which bio-ink works and the way it may be printed – the spray course of was mainly involved with the machine itself and the way to management three streams of supplies.

Accordingly, the 2 processes are at totally different phases of growth. Antorveza Paez stories that the spray course of nonetheless requires considerably extra analysis into its mechanical properties, reminiscent of when it comes to how the grains and bonding medium are organized inside the thing.

Fascinated by nature’s ingenuity

For Antorveza Paez, working with microorganisms means one factor above all else: forging a brand new relationship with constructing supplies.

“As an architect, you don’t usually know something about what went into making a fabric – it’s manufactured some place else”, she says. “I’m fascinated by the truth that nature has discovered methods of producing very refined supplies and that we will make these relevant to the issues we face at this time.”

The architect is at the moment engaged on a 3rd examine involved with the environmental impression of biocementation and discovering related options. The rationale for that is that ammonium, which is produced through the response involving the micro organism and mineralisation tub, could be very damaging to the setting.

As Antorveza Paez explains: “If we don’t issue the disposal of this chemical by-product into our designs, then sadly utilizing biocement for development received’t be such a sustainable follow.”

Load-bearing buildings nonetheless a great distance off

The researcher admits that, as issues at the moment stand, biocementation is extra alongside the strains of mortar than concrete. Her comparability with concrete makes it clear how a lot analysis continues to be wanted.

The formulation for concrete – specifying what number of grains of every dimension are mixed and in what proportions – has been refined for over a century and continues to be fine-tuned to at the present time.

Within the case of biocementation, this work is just simply getting began: whereas we all know that micro organism can, in precept, be mixed with sure grain sizes, the query of the way to use this to provide a long-lasting materials that’s as steady as potential is but to be answered by analysis.

“The large query is not whether or not biocement works, however moderately how effectively its properties might be managed,” concludes Antorveza Paez.

Video

References

• Antorveza Paez KA, Kindler RO, Terzis D, Dutto A, Pleij T, Zorzetto G, Studart AR, Dillenburger B: 3D biocement printing: scaling up residing mineral buildings. NPJ Supplies Sustainability 2026, 4: 20, DOI: 10.1038/s44296-026-00110-1
• Antorveza Paez KA, Kindler RO, Terzis D, Lin CW, Coulter FB, Dillenburger B: Robotic biocementation spraying: a bioinspired fabrication methodology for architectural surfaces. Architectural Intelligence 2026, 5: 11, DOI: 10.1007/s44223-026-00120-y
• Antorveza Paez KA, Huang S, Yeh KH, Seav Okay, Dillenburger B. Design workflow for porous 3D-printed biocement geometries. Biotechnology Design. 2026, 4: 40, DOI: 10.1017/s2977905726100286

Predominant picture: Kintek furnace firing and melting rocks, courtesy of Kintek