Bacteria create bio-concrete Sandy soil isn’t a stable basis for building a house. This is why an EPFL spin-off is consolidating it with the help of micro-organisms. Text: Florian Fisch Illustration: ikonaut Soil bacteria from the region A crumbling substructure? An unstable coastline? There are lots of ways to consolidate ground like this. But they often rely on harmful chemicals or expensive construction methods. A biological solution, however, can build on the capabilities of bacteria present in the local soil. Multiplying in the bio-reactor In the labs of the spin-off company Medusoil in Lausanne, the right micro-organisms are selected and multiplied. They can then either be freeze-dried – like the dried yeast we use to bake bread – or fed straight into largescale bio-reactors on the building site. Afterwards, they’re injected into the soil.
Biological concrete Once they’re in the soil, the bacteria (black in the image) consume the urea that has also been injected into the soil, turning it into carbonate, one of the chemical components of lime. The other component is calcium, which is usually present in the soil but can also be injected into it. The lime crystals (white) bond with the grains of sand (beige) or other soil particles to create a kind of concrete. You don’t need to use a quarry or a cement kiln. The only thing for which there isn’t yet a bio-version is the plastic meshing that Medusoil uses.
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