Students at the University of Cape Town have developed a bio-brick that mixes sand, bacteria and human urine. Unsurprisingly, it is the world's first building material to be made from the liquid waste high in nitrogen and phosphorous.

The brick is created through a process called microbial carbonate precipitation, a complex reaction that has many applications. It has been used to improve concrete's durability, as a historical preservation technique on stone, and as a way of improving soil. 

Here, when urine is mixed with sand and bacteria, the resulting chemical reaction produces calcium carbonate, which hardens the mixture and forms the brick. According to the scientists, it is similar to the way seashells are formed. 

Each brick requires about 25 to 30 liters of urine, or roughly 100 bathroom trips, and is collected from a fertilizer-producing urinal. The by-product of the brick making process is used again to create a second fertilizer as well. 

UCT master’s student Suzanne Lambert, who worked with Dr Dyllon Randall and fellow classmate Vukheta Mukhari to develop the technique, says there are many benefits to this process. Not only does  the technique make something useful out of a plentiful waste, but it also does not require the heat needed for traditional brick making. Instead of being kiln-fired, which releases carbon dioxide into the air, the bio-bricks are molded at room temperature. 

The bio-brick is effectively zero waste and has great potential to become at truly sustainable construction material. “In this example you take something that is considered a waste and make multiple products from it" said Dr Dyllon Randall. "You can use the same process for any waste stream. It’s about rethinking things," he added.