Living, breathing buildings: 3D-printed material that eats CO₂

A new photosynthetic material developed by researchers at ETH Zurich can grow, harden, and remove carbon dioxide from the atmosphere — all while staying alive.

The breakthrough relies on cyanobacteria, ancient microbes capable of efficient photosynthesis even under low light.

Embedded in a printable hydrogel, these bacteria form a living structure that grows using only sunlight, CO₂, and nutrient-rich artificial seawater. Over time, the bacteria not only builds biomass but also trigger mineralisation, hardening the material and storing carbon in solid form.

“As a building material, it could help to store CO₂ directly in buildings in the future,” says project leader Mark Tibbitt, a Professor of Macromolecular Engineering at ETH Zurich.

“The material can store carbon not only in biomass, but also in the form of minerals – a special property of these cyanobacteria.”

“Cyanobacteria are among the oldest life forms in the world,” says co-author Yifan Cui. “They are highly efficient at photosynthesis and can utilise even the weakest light to produce biomass from CO₂ and water.”

As the bacteria photosynthesise, they change the chemical environment outside their cells, prompting the formation of solid carbonates such as lime.

These minerals are deposited within the material itself, reinforcing the structure over time. In this way, the cyanobacteria gradually harden the initially soft forms.

Laboratory tests showed that the material continuously binds CO₂ for 400 days. Most of it is in mineral form – around 26 milligrams of CO₂ per gram of material, significantly more than many biological approaches and comparable to the chemical mineralisation used in recycled concrete, which binds around 7 milligrams per gram.

The carrier for the bacteria is a hydrogel: a soft, water-rich gel made of cross-linked polymers. This allows the living cells to remain active while the structure grows and solidifies.

^{Continuous culture over 400 days: Freshly printed, the structure is still soft. After 30 days it can stand free and greens up visibly. It continuously stores CO2 and hardens from the inside. (Scale: 1 cm). Credit: Yifan Cui / ETH Zurich.}

“In this way, we created structures that enable light penetration and passively distribute nutrient fluid throughout the body by capillary forces,” says researcher Dr, Dalia Dranseike, a materials scientist and process engineer. 

The team sees the living material as a low-energy, environmentally friendly alternative to more industrial forms of carbon capture. 

“In the future, we want to investigate how the material can be used as a coating for building façades to bind CO₂ throughout the entire life cycle of a building,” says Tibbitt. 

While the technology is still experimental, it’s already capturing the imagination of architects.

At the Venice Architecture Biennale, the team exhibited their work at the Canadian Pavilion. They used the printed gel to create two tree-trunk-like structures, the tallest around three metres high.

Thanks to the cyanobacteria, each of these experimental towers can bind up to 18 kilograms of CO₂ per year — roughly equivalent to the annual carbon capture of a 20-year-old pine tree in a temperate climate.

“The installation is an experiment – we have adapted the Canada Pavilion so that it provides enough light, humidity and warmth for the cyanobacteria to thrive, and then we watch how they behave,” says ETH doctoral student Andrea Shin Ling.

These findings are published in Nature Communications.