SCIENTISTS HAVE turned urine into bio-concrete, as part of a movement to revolutionize sustainable construction by creating building materials from waste. The research team used biomineralization, a biotechnological process where bacteria convert urea found in urine into calcium carbonate crystals.
These large circular crystals with radial striations with smooth surfaces bind sand particles together, resulting in a strong and environmentally friendly bio-concrete chemically similar to natural sandstone.
The project was initiated as the researchers recognized urine as an abundant yet underutilized resource, prompting them to explore microbial biomineralization as a sustainable alternative to traditional concrete production.
While concrete remains the most widely used building material globally with approximately four billion tons produced annually, its huge environmental cost pushes the construction sector to seek more sustainable alternatives.
Producing cement, its key ingredient, requires heating limestone to temperatures of about 2,642 degrees Fahrenheit (1,450 degrees Celsius), consuming large amounts of energy and releasing significant greenhouse gas emissions.
In order to address this environmental challenge, the research team developed bio-concrete as a promising substitute, through an innovative method that integrates into a “wastewater-bio-concrete-fertilizer” value chain, transforming a common waste product into valuable construction materials and fertilizers simultaneously.
They mixed a powder containing bacteria with sand, placed the mixture into a mold, and then flushed it with calcium-enriched urine for three days in an automated process. The breakdown of urea by the bacteria, combined with adding calcium to the urine, causes crystals of calcium carbonate to grow.
The process solidifies the sand mixture into bio-concrete, ultimately producing a solid that is chemically similar to natural calcareous sandstone. Depending on the mold, elements can be created in various shapes and sizes, with a current maximum depth of 15 centimeters.
According to the researchers, when using technical-grade urea, the bio-concrete achieved compressive strengths surpassing 50 megapascals (MPa), making it considerably stronger than previously available biomineralized materials.
Meanwhile, tests with artificial urine produced strengths of 20 MPa, while real human urine resulted in strengths of around 5 MPa, due to a decline in bacterial activity during processing.
The team is currently assessing the bio-concrete’s resilience under freeze-thaw conditions, determining its suitability for outdoor applications. The project’s second phase will focus on optimizing bacterial activity and further refining the production process. By Manny Palomar, PhD (EV Mail JUNE 9-15, 2025 Issue)
