Researchers at the University of Stuttgart have developed an innovative way to produce sustainable building material from human urine.
This breakthrough, known as “bio-concrete,” is part of a larger project called “SimBioZe,” which aims to create a circular economy by turning waste into valuable products.
The project has gained attention for its potential to significantly reduce the environmental impact of concrete production.
Concrete is one of the most widely used building materials in the world, with around 4 billion tons of cement being processed every year.
However, the traditional way of making cement is energy-intensive and produces large amounts of greenhouse gases.
To create cement, materials are fired at temperatures of around 1,450 degrees Celsius, consuming vast amounts of energy and contributing heavily to carbon emissions.
In contrast, the bio-concrete developed at the University of Stuttgart is produced through a natural, microbial process called biomineralization, which uses much less energy and generates far fewer emissions.
The key to this process is human urine, which the researchers describe as an abundant and previously overlooked resource.
The method involves mixing bacteria with sand and placing the mixture into a mold.
Over three days, the mold is flushed with calcium-enriched urine, allowing the bacteria to break down urea and create crystals of calcium carbonate. These crystals bind the sand together, forming a solid structure that is chemically similar to natural sandstone.
This innovative method has been published in the journal npj Materials Sustainability.
The first tests of this bio-concrete have shown promising results. When technical urea is used, the material achieves a compressive strength of over 50 megapascals, which is stronger than many other biomineralized building materials.
Even with artificial urine, the concrete reaches 20 megapascals. However, with real human urine, the strength drops to five megapascals, as the bacteria become less active during the three-day process.
The researchers are now working to understand what substances in human urine reduce bacterial activity so they can optimize the process.
The team is also testing the material’s ability to withstand outdoor conditions, including freeze-thaw cycles. According to the researchers, if they can achieve a strength of 30 to 40 megapascals, the material could be suitable for constructing buildings up to three stories high.
A major advantage of bio-concrete is its minimal environmental impact. Unlike traditional cement, which requires massive amounts of heat and energy, bio-concrete is made at room temperature using natural processes.
Additionally, the water in human urine eliminates the need for extra water during production, making the process even more sustainable.
The project is now moving into its second phase, supported by a grant from the Baden-Württemberg Ministry of Science, Research, and the Arts. The researchers plan to optimize the manufacturing process and begin real-world testing.
They envision collecting urine at high-traffic places like airports, turning it into bio-concrete and fertilizer in a pilot facility at Stuttgart Airport. This approach not only produces sustainable building material but also recycles nutrients for agriculture.
The researchers believe that with further development, this sustainable building method could revolutionize the construction industry, offering a green alternative to traditional concrete while turning waste into something valuable.
