Can bacteria unlock green construction?

This process harnesses bacteria to produce carbon-binding cement

Spotted: Concrete has a huge carbon problem. Its production accounts for 8 per cent of global carbon emissions, and this proportion is only getting bigger as construction ramps up around the world. And according to the International Energy Agency (IEA), we are off track as decarbonisation is pitted against economic growth.

A large proportion of concrete-related emissions come from cement, the main ingredient that goes into making the ubiquitous building material. Sustainable alternatives are needed, and a team of researchers from the Fraunhofer Institute for Ceramic Technologies and Systems (IKTS) believes it has the answer in the form of biogenic construction materials made by cyanobacteria. The researchers’ process not only avoids burning calcium carbonate, the source of CO2 emissions, but can also capture and bind the greenhouse gas, turning concrete from a climate problem to a climate solution. 

Cyanobacteria, previously known as blue-green algae, are not plants, but they are capable of photosynthesis. If placed in a nutrient solution under light, they are driven to multiply, and when Fraunhofer researchers added aggregates like sand or basalt to the mix, they discovered that rock-like porous structures form using biogenic calcium carbonate as a binder. This can then be used as a base for sustainable building materials. What’s more, the newly discovered biological process mimics the formation of stromatolites, limestone deposits that naturally sequester carbon, and the researcher’s bacteria-based structures also absorb and bind CO2 in a similar way. 

Clearly, this discovery holds significant environmental benefits. According to Dr. Matthias Ahlhelm, who is project manager of this research and group manager within the IKTS, the hope is to “offer biogenic, climate-neutral or even climate-negative sustainable materials. But, we need to prove its feasibility of course, regarding must-have properties.” The cultivation process, shaping methodology, and mineralisation procedure all need to be scaled up and tested for economic viability, but initial results look promising. The calcium carbonate material can be shaped by spraying, foaming, and extrusion, making it highly versatile. And it is even compatible with 3D printing, as shown in this related piece of research, published in Frontiers of Bioengineering and Biotechnology. Potential applications are also wide, ranging from insulation to brick and mortar, and the lack of toxic substances often found in conventional building products adds yet another edge. 

While the material is currently undergoing testing for industrial-scale production, the researchers are optimistic and on the lookout for how to “further incorporate circular economy thinking and usage” into their work. They are exploring how to make use of mine waste and dairy byproducts in the production process, further reducing the environmental footprint of the construction industry.

Written By: Oscar Williams