tech2 News Staff Oct 29, 2018 12:00 PM IST
A first of its kind brick made from human urine was revealed on Friday by its inventors – a group of master’s civil engineering students at the University of Cape Town – in an innovate twist to waste recovery.
The ‘bio-brick’ was made by tapping into a natural pathway that bacteria use to break down urea.
“It's not unlike the way seashells are formed,” Dr Dyllon Randall, advisor to the students told university press.
Loose sand with urease-producing bacteria were raw materials in the process. The urease breaks down the urea in human urine and produces calcium carbonate in the process, giving sand a little more structure and form. The calcium carbonate could then be moulded into shape to make columns or rectangular building bricks, like those made by the students.
The group experimented with different brick shapes and strengths to make bricks, which were later tested and reworked with assistance from their supervisors.
Unlike regular bricks, which are made using temperatures of 1,400ºC in a kiln-fired process that releases large amounts of carbon dioxide, these bio-bricks made from urine can be ‘grown’ at room temperature.
"The longer you allow the little bacteria to make the cement, the stronger the product is going to be. We can optimise that process," Randall told university press.
A secondary product from the novel urine-upcycling study was biofertiliser. The high nitrogen and potassium content of urine was also harnessed in the process, since they are important components in chemical fertilisers.
The collected urine was processed in three stages, beginning with producing a solid fertiliser form the raw urine. The residual liquid was processed with bacteria to produce bio-bricks that utilise just calcium and carbonate from the mixture.
The remaining liquid was then used to make a secondary fertiliser, effectively making the entire process zero-waste, a university press report said.
While the concept of bricks made from urine was tested using artificial compounds, this study is the first to use real human urine to produce a useful recycled product.
The study was recently published in the Journal of Environmental Chemical Engineering.