SA Affordable Housing January - February 2019 // Issue: 74 | Page 8

NEWS
To pee or not to pee...
UCT students have developed a new bio-brick, which while offer-
ing no current threat to present production methods, offers up an
innovative solution in the sustainable housing space.
T
he 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.
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JANUARY - FEBRUARY 2019
"You take something that is
considered waste and make
multiple products from it."
“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.
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