Wonderful Engineering

Your Urine Can Now Be Used To Make Bricks For Construction

An unusual bricks making ingredient, urine, was discovered by University of Cape Town Masters research student Suzanne Lambert. According to Lambert’s supervisor, Dr. Dyllon Randall, human urine is the ‘liquid gold.’ He said that urine accounts for less than 1% of the domestic wastewater, but it contains 80% of the nitrogen, 56% of the phosphorus and 63% of the potassium of this wastewater. The urine for this experiment was collected from temporary urinals placed in the university campus. The receptacles also had builders lime in it which is a material that reacts with the phosphorus in urine to produce fertilizer.

After the fertilizer is extracted, the remaining liquid is used in the brick making process. The residual urine contains high levels of naturally occurring urea. The solution is mixed with loose sand, and the mixture is allowed to be colonized by a type of bacteria which produces the enzyme urease. Urease is secreted by the bacteria that breaks down the urea and produces calcium carbonate. This is the same compound which gives strength to the eggshells. It solidifies the loose sand particles together and bonds everything to form a dense brick. The more time bacteria spend inside the mixture, the stronger the bricks become.

The bricks made of urine use less energy to produce than regular brick. Randall said, “If a client wanted a brick stronger than a 40% limestone brick, you would allow the bacteria to make the solid stronger by ‘growing’ it for longer. The longer you allow the little bacteria to make the cement, the stronger the product is going to be. We can optimize that process.” The discovery of the process is not something new however its application in forming bricks is a game changer. The main ingredient that is the human urine is in infinite supply. The research has opened doors to the new ways of inexpensive and low tech ways to build a brick. The engineering team of the research is working on the brick’s development. Randall said, “No-one’s looked at it regarding that entire cycle and the potential to recover multiple valuable products. The next question is how to do that in an optimized way so that profit can be created from urine.”