To create the bio-concrete, the researchers employed biotechnology. A powder containing bacteria is added to sand, which fills a mould. This mixture is rinsed for three days with urine enriched with calcium. The bacteria break down urea, leading to the growth of calcium carbonate crystals and the hardening of the sand mixture into bio-concrete. The result of this process, known as biomineralisation, is a solid material chemically similar to natural calcium sandstone.
Promising alternative
The new bio-concrete offers an alternative to traditional cement-based concrete. “Our production process consumes significantly less energy and causes fewer emissions than traditional cement production,” says Professor Lucio Blandini, Director of ILEK. “But our approach is also sustainable because we embed the product in a circular value chain.”
In the next phase, researchers will focus on identifying contaminants in human urine that affect bacterial activity to optimise the production process. Simultaneous fertiliser production will also receive additional attention in collaboration with the University of Hohenheim’s Centre for Ecological Agriculture. The ultimate goal is a practical test at Stuttgart Airport, where urine will be collected and processed into both bio-concrete and fertilisers.
Initial tests have been promising. Using technical urea, the team achieved an impressive compressive strength of over 50 Megapascals (MPa), significantly higher than existing biomineralisation-based construction materials. The strength achieved with actual human urine is currently lower, at 5 MPa, but researchers believe this can be improved. A strength of 30 to 40 MPa would be sufficient for the masonry of two to three-story buildings. The material’s resistance to frost and thaw is currently being investigated to enable outdoor applications.
For more information on SimBioZe, visit the University of Stuttgart website.
Bioclear Earth, a spin-off from the University of Groningen, has been researching the production of urea- and calcium-based bio-concrete for several years. Read more about it in “Using bacteria to manufacture bio-concrete” (article, Agro&Chemistry, 2 October 2020).
Image: Alexander Limbach/Shutterstock
