A building material that lives and stores carbon

The idea seems to be futuristic: At ETH Zurich, different disciplines work together to combine conventional materials with bacteria, algae and fungi. The common goal: to create living materials that acquire useful properties thanks to the metabolism of microorganisms – “like the ability to bind CO₂ From air through photosynthesis, “says Mark Tibbitt, professor of macromolecular engineering at ETH Zurich.

An interdisciplinary research team, led by Tibbitt, has now converted this vision into reality: it has stable photosynthetic bacteria – known as cyanobacteria – integrated into a printable gel and developed a living material, grows and actively carbon from the air. The researchers recently presented their “Photosynthetic Living Material” in a study in the magazine Natural communication.

Key feature: dual carbon sequestration

The material can be shaped with 3D printing and only requires sunlight and artificial sea water with slightly available nutrients in addition to CO₂ grow. “As a building material, it could help to save CO₂ Directly in buildings in the future, ”says Tibbitt, who included research to live materials at ETH Zurich.

The special thing about it: the living material decreases a lot more CO₂ when it binds through organic growth. “This is because the material can be kept carbon not only in biomass, but also in the form of minerals – a special property of these cyanobacteria,” says Tibbitt.

Yifan Cui, one of the two main authors of the study, explains: “Cyanobacteria are among the oldest ways of life in the world. They are very efficient in photosynthesis and can even use the weakest light to produce biomass from CO₂ and water “.

At the same time, due to photosynthesis, the bacteria change their chemical surroundings outside the cell, so that solid carbonates (such as lime) fail. These minerals represent an additional carbon sink and in contrast to biomass – Store Co.₂ in a more stable form.

Cyanobacteria as a master builder

“We use this ability especially in our material,” says Cui, who is a doctoral student in the Tibbitt research group. A practical side effect: the minerals are deposited in the material and strengthen it mechanically. In this way, the cyanobacteria slowly hardens the initially soft structures.

Labort tests showed that the material continuously binds CO₂ over a period of 400 days, most of them in a mineral form – around 26 milligrams of CO₂ per gram of material. This is significantly more than many biological approaches and comparable to the chemical mineralization of recycled concrete (approx. 7 mg CO₂ per gram).

Hydrogel as a habitat

The carrier material, which houses the living cells, is a hydrogel-in gel made of networked polymers with a high water content. The Tibbitt team selected the polymer network so that it can transport light, Co.₂Water and nutrients and enables the cells to spread evenly inside without leaving the material.

To ensure that the cyanobacteria live as long as possible and remain efficient, the researchers have also optimized the geometry of the structures using 3D printing processes in order to increase the surface, increase light penetration and to promote the nutrient flow.

The co-first author Dalia Dransieke: “In this way we have created structures that enable a light penetration and passively distribute nutrient fluid through the body through capillary forces.” Thanks to this design, in which the capsized cyanobacteria lived productively for more than a year, the material researcher in the Tibbitt team is happy to report.

Infrastructure as a carbon sink

The researchers see their living material as a low -energy and environmentally friendly approach that can bind CO₂ From the atmosphere and complement existing chemical processes for carbon binding. “In the future we would like to investigate how the material can be used as a coating for the construction of facades to bind CO₂ During the entire life cycle of a building “Tibbitt looks ahead.

It is still a long way in front of you – but colleagues from the field of architecture have already taken up the concept and realized initial interpretations in an experimental way.

Two installations in Venice and Milan

Thanks to the ETH Doctoral student Andrea Shin Ling, the basic research of the ETH laboratories has taken the large stage of the architectural biennals in Venice. “It was particularly difficult to increase the production process from laboratory format to room dimensions,” says the architect and organic designer, who is also involved in this study.

Ling received his doctorate in the ETH professor Benjamin Dillenburger's chairman of Digital Building Technologies. In her dissertation, she developed a platform for biofabrication that can print living structures that contain functional cyanobacteria on an architectural level.

For the Picoplanktonic installation in Pavilion, Canada, the project team used the printed structures as living building blocks to build two tree-like objects, the largest around three meters high. Thanks to the cyanobacteria, they can bind up to 18 kg of CO₂ As much as a 20-year-old jaw in the temperate zone per year.

“The installation is an experiment – we have adapted the Canada pavilion so that it offers enough light, moisture and warmth so that the cyanobacteria can thrive, and then we watch how they behave,” says Ling. This is an obligation: the team monitors and maintains the installation on site. Until November 23.

On the 24th Triennale di Milano, Dafne's skin examines the potential of living materials for future construction envelopes. On a structure covered with wooden shingles, microorganisms form a deep green patina that changes the wood over time: A sign of the decay becomes an active design element that binds Co.₂ And emphasizes the aesthetics of microbial processes. Dafnes skin is a collaboration between Maid Studio and Dalia Dransieke. It is part of the exhibition “We The Bacteria: Notes for Biotic Architecture” and runs until November 9th.

The material of the Photosynthetic Living was created thanks to interdisciplinary collaboration within the framework Lively (advanced engineering with living materials). The ETH Zurich initiative promotes cooperation between researchers from various disciplines in order to develop new living materials for a variety of applications.