Students at University of Cape Town have created bricks using sand, human urine and bacteria, claiming to be the first to do so.

The Bio-bricks are created through a natural process called microbial carbonate precipitation, similar to the way seashells are formed. Loose sand, which has been colonised with 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 shape.

While regular bricks are kiln-fired at temperatures of 1,400ºC producing large amounts of carbon dioxide, bio-bricks do not require heat. The bricks initially smell of ammonia but the smell disappears after 48 hours, the students' supervisor said.

The idea of using urea to grow bio-bricks has previously been tested in the US using synthetic products.