The construction industry is not necessarily considered to be environmentally friendly: around six percent of global carbon dioxide emissions are produced in the production of cement. More carbon dioxide is released when the concrete that was made from the cement hardens. Scientists from the United States have developed a building material that is significantly more environmentally friendly than conventional concrete and has another very practical property: it can multiply.
The material developed by researchers led by Wil Srubar from the University of Colorado in Boulder consists of sand, a hydrogel and a bacterium that drives photosynthesis. The researchers created a scaffold out of the sand, the hydrogel contains water and food for the bacteria so that they can live and multiply.
The cyanobacteria of the genus Synechococcus produce lime, similar to mussels, which clogs the structure. This creates a living material that is as stable as cement mortar. "It looks like Frankenstein-like material,". said Srubar, "That's exactly what we're trying to create: something that stays alive."
Under the right conditions, which means the presence of moisture and nutrients, the bacteria not only stay alive, but multiply. The researchers shared a building block made from the organic building material and added sand, hydrogel and nutrients. Within a few hours, the two half blocks had become two whole. The researchers went on like this and finally received eight building blocks in the third generation.
The advantage is that building materials can be produced without emissions in this way. However, there is also a downside: in order for the material to reach its maximum strength, it must be completely dry. But then the bacteria that need moisture to live suffer.
The researchers must therefore find a compromise between dryness for strength and moisture for the viability of the microorganisms. On the other hand, they can use humidity and temperature like switches to control when the bacteria grow and when the material is at rest and fulfills its structural function.
The project, the Srubar and his team in the Matter magazine, belongs to the research area Engineered Living Materials (ELMs). Researchers mix inanimate matter with living organisms, mostly bacteria. This gives them materials with new properties, such as those that react to light, recognize pressure or have an antimicrobial effect.