BBC– Human urine has been used to create environmentally friendly bricks by university students in South Africa.
They combined urine with sand and bacteria in a process that allows the bricks to solidify at room temperature.
“It’s essentially the same way that coral is made in the ocean,” Dyllon Randall, their supervisor at the University of Cape Town, told the BBC.
Regular bricks need to be baked in high-temperature kilns that produce large amounts of carbon dioxide.
The engineering students at the University of Cape Town (UCT) have been harvesting urine from men’s toilets.
After first making a solid fertiliser, the leftover liquid is then used in a biological process “to grow” what the university calls “bio-bricks”.
The process is called microbial carbonate precipitation.
The bacteria produces an enzyme that breaks down urea in the urine, forming calcium carbonate, which then binds the sand into rock hard, grey bricks.
But after about 48 hours, the bricks completely lose the ammonia smell – and they do not have any health risks either, he said.
“The process we use in stage one kills all harmful pathogens and bacteria because we operate at an extremely high pH that has been shown to kill pretty much everything.”
According to UCT, the concept of using urea to grow bricks was tested in the US some years ago using synthetic urea, which requires a lot of energy to produce.
The bricks produced by Dr Randall and his students, Suzanne Lambert and Vukheta Mukhari, use real human urine for the first time, which offers opportunities for recycling waste.
They take between four and six days to grow – if you want a stronger brick you leave it for longer.