There is nothing more human than trying to turn problems into opportunities. And what problem is more everyday and universal than our bodily waste? While most of us think of urine as simply something to be eliminated, a group of researchers from theUniversity of Stuttgart he had a brilliant and somewhat provocative intuition: use it as a raw material to produce building materials. In a world desperately seeking alternatives to traditional concrete, responsible for approximately 8% of global CO2 emissions, this strange idea could turn out to be ingenious. Through a process of biomineralization, urea-rich urine becomes the key ingredient of a bioconcrete with impressive mechanical properties and a drastically reduced ecological footprint.
An idea that โsolidifiesโ quickly
The cement industry it is a polluting giant that shows no signs of slowing down its activity. Approximately 4 billion tons of cement are produced worldwide each year., with devastating consequences for the environment. Professor Lucio Blandini, director of the Institute for Lightweight Structures and Conceptual Design (ILEK) at the University of Stuttgart, highlights an alarming fact (which, if you follow us, you already know):
Conventional concrete is typically fired at temperatures around 1.450 degrees. This consumes a lot of energy and releases large amounts of greenhouse gases.
To address this problem, three institutes at the University of Stuttgart have joined forces to develop a bioconcrete, an innovative material produced through microbial processes. I was particularly struck by the ingenuity of the process: They mix a powder containing bacteria with sand, place it in a mold, and then irrigate it with calcium-enriched urine for three days in an automated process. The breakdown of urea by the bacteria, combined with the addition of calcium, causes calcium carbonate crystals to grow, which solidify the mixture.
From urine to foundations
The first samples produced show promising properties. The team has reached a compressive strength of over 50 megapascals, significantly exceeding the resistance of previously available building materials produced through biomineralization. With urea in artificial urine, it was achieved a resistance of 20 megapascals, while with real human urine the value was 5 megapascal (bacteria lose activity during the three-day mineralization period).
According to the researchers, a resistance of 30-40 megapascals would be sufficient to construct two- or three-story buildings. They are currently conducting freeze-thaw tests to determine whether the material can be used outdoors. Mayia Smirnova, a researcher at ILEK, explains that the final product is chemically similar to natural calcareous sandstone and can be molded into various shapes, with a maximum depth (at the moment) of 15 centimeters.
Circular economy: a bit of toilet, a bit of construction site
The beauty of this approach is not only the reduction of CO2 emissions, but also the integration into a circular economy. In his study published here, the team developed a concept showing how urine could be separated and processed from the partial wastewater flow in places with a high volume of people, such as an airport, to be used as a raw material for the production of bioconcrete. At the same time, this process could recover valuable secondary substances from the wastewater to produce fertilizer for agriculture. Blandini points out:
By producing two products at the same time, we increase the environmental benefits.
A solution that transforms a problem (wastewater disposal) into a double opportunity: building materials and fertilizers. Perfect example of circular thinking.
Next steps: from theory to practice
After successfully completing the preliminary studies, the project was extended for three years by Baden-Wรผrttemberg Ministry of Science, Research and the Arts. In further laboratory tests, the researchers want to identify substances in human urine that have a negative effect on the activity of the bacteria and thus on the quality of the bioconcrete.
The production process will be optimized on this basis. The team, together with the Center for Organic Agriculture at the University of Hohenheim, is also focusing on the simultaneous production of fertilizers. Once the laboratory tests are completed, the concept will be tested under real conditions: a pilot plant is planned at Stuttgart Airport, where urine will be collected and processed into bioconcrete and fertilizer.
Believe it or not, our urban future could be built with what we throw away without thinking today. I like to think that this research perfectly represents the human ability to see resources where others, including ourselves, only see waste.
