University of Cape Town researchers created the world's first "bio-bricks" made from sand, bacteria, and human urine collected from special toilets in the engineering school's bathrooms. From The Guardian:
Bio-bricks are created through a natural process called microbial carbonate precipitation, said (project supervisor and water quality engineering lecturer Dyllon) Randall, 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 1,400C and produce large amounts of carbon dioxide, the bio-bricks do not require heat.
"If a client wanted a brick stronger than a 40% limestone brick, you would allow the bacteria to make the solid stronger by 'growing' it for longer," said Randall…
Randall described urine as liquid gold. By volume, urine accounts for less than 1% of domestic waste water, but it contains 80% of the nitrogen, 56% of the phosphorus and 63% of the potassium found in waste water.