UCT students have developed a new bio-brick, which while offering no current threat to present production methods, offers up an innovative solution in the sustainable housing space.

The bio brick, developed by the University of Cape Town students, is made in moulds at room-temperature removing the need for high-temperature kilns and uses as its main ingredient – human urine.

The urine, gathered from a system of urinals at the engineering block at the university, is mixed with sand and bacteria in a process called microbial carbonate precipitation.

In a system that mimics the creation of sea shells, loose sand – which has been colonised with a strand of bacteria that produces urease – is mixed with the urine. Urease breaks down the urea in the urine, producing calcium carbonate, which cements the sand into a brick shape.

While regular bricks are kiln-fired at temperatures of 1 400°C and produce large amounts of carbon dioxide the only by-products of this new method are nitrogen and potassium, which are used in commercial fertilisers.

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 project supervisor Dr Dyllon Randall, a senior lecturer in water quality engineering at the University of Cape Town and his students – Suzanne Lambert and Vukheta Mukhar – uses real human urine for the first time.

“In this example you take something that is considered waste and make multiple products from it. You can use the same process for any waste stream. It’s about rethinking things,” Randall told The Guardian.

Randall explains that the strength of the brick is determined by the length of time for which it is allowed to grow, with early bricks taking between four and six days to grow to the strength of a 40% limestone brick.

“Just a few months later we’ve doubled that strength now just by changing the material we put into the mould and allowing the bacteria to cement the particles for longer – with zero heat, at room temperature,” Randall told BBC’s Newsday programme.

It takes between 25ℓ and 30ℓ of urine to grow just one brick, but Randall is quick to stress that most of this urine is also used to produce about 1kg of fertiliser.