A team of materials scientists from the Swiss Federal Institute of Technology (ETH) in Zurich has developed a new “living” material that incorporates cyanobacteria and absorbs carbon dioxide (CO2). Over time, it hardens and can be used in construction.
Because it contains cyanobacteria, the material performs photosynthesis: using sunlight and water, it converts CO2 into oxygen and sugars that fuel growth.
With the right nutrients, the material can also transform CO2 into solid carbonate minerals, such as limestone, the team found. Eventually, these minerals create a robust framework within the material, strengthening it and storing carbon in a more stable form than biomass alone.
“The material can store carbon not only in biomass but also in the form of minerals (a unique property of these cyanobacteria). As a building material, it will help in the future to sequester CO2 directly in buildings,” said co-author Mark Tibbitt, an assistant professor in the Department of Macromolecular Engineering at ETH.
Without the ability to isolate carbon in mineral form, the new material would remain flexible and jelly-like, Live Science reported. By producing a mineral skeleton from CO2 and nutrients, the material gradually increases its mechanical strength, making it a strong candidate for construction, the researchers say.
They also think the material could be applied as a coating on building facades to absorb CO2 directly from the atmosphere. During the study, the material continuously absorbed carbon dioxide for 400 consecutive days, retaining about 26 milligrams of CO2 per gram of material as carbonate deposits. That rate is significantly higher than other biological carbon-absorption methods.
The increasingly vibrant green color of the material indicates that it is storing CO2 as biomass. However, cyanobacteria can only grow to a certain extent, and the rate at which cells stored carbon leveled off after about 30 days. That means carbon sequestration as biomass decreases after this period, though it does not stop.
The foundation of the new material is a 3D-printed hydrogel with a high water content, made of cross-linked molecules. The researchers chose a porous hydrogel and cultivated cyanobacteria within it, ensuring adequate light, water, and CO2 penetration. The team then tested various forms of the hydrogel to determine which supported cyanobacterial survival best.
“Cyanobacteria are one of the oldest forms of life on Earth. They are highly efficient at photosynthesis and can utilize even the faintest light to produce biomass from CO2 and water,” said co-author Ifan Tsui.
During the study, the scientists immersed the hydrogels in artificial seawater to supply the nutrients needed for mineral deposition. The team now needs further research to determine how to incorporate those nutrients, particularly calcium and magnesium, into material intended for building surfaces.
The researchers are also experimenting with different shapes the “living” material could take. At an architectural exhibition in Venice, the team presented it in the form of two objects resembling tree trunks. Each could absorb about 18 kilograms of CO2 per year — roughly the same as a 20-year-old pine tree.
The scientists said cyanobacteria could be genetically modified to increase their photosynthesis rate before being embedded in the material.
The results of the study were published in the journal Nature Communications.
