A group of researchers from the University of Cape Town, in South Africa, has developed a brick whose production is considered 100% eco-friendly. The raw material for the invention is human urine.
Professor Dyllon Randall and engineering undergraduates Suzanne Lambert and Vukheta Mukhari first used organic input to develop a solid fertilizer formula. The problem is that there was liquid left, which could not be wasted. The team then developed a new biological process involving urine plus sand and bacteria, resulting in the so called “bio-bricks.”
"It's essentially the same way by which coral is made in the ocean,” professor Dyllon Randall explained, in an interview to BBC World News. “Chemically speaking, urine is liquid gold,” he justified. This happens because liquid is responsible for at least 1% of household wastewater (in volume), but contains 80% of nitrogen, 56% of phosphate and 63% of potassium of this same wastewater.
Moreover, about 97% of phosphate present in the urine can be converted into calcium phosphate, the fertilizer key ingredient that sustains commercial agriculture worldwide.
How are they manufactured?
The biological process that urine, sand and bacteria undergo is called microbial carbonate precipitation. It works like this: A set of sand is colonized with bacteria that produce urease enzyme; this enzyme breaks down the urea present in the urine forming a calcium carbonate substance. This complex chemical reaction solidifies the sand, making the compound as hard as rock.
“The longer you allow the little bacteria to make the cement, the stronger the product is going to be. We can optimize that process, allowing the bacteria to make the solid stronger by ‘growing’ for longer,” added Randall. On average, each “batch” requires four to six days to complete.
All urine used in the experiment was collected from male restrooms. Also, a huge amount of liquid was necessary. Each bio-brick requires 25 to 30 liters to be produced - and, on average, each time someone goes to the bathroom, they produce around 200 ml to 300 ml, meaning, about 100 people are needed for each brick.
Eco-friendly and no health threat
What makes bio-bricks so sustainable from an environmental perspective is not the input, but how to make it. Manufacturing conventional bricks requires oven-burnt materials to temperatures about 1,400 °C (2,550 °F), producing a great amount of carbon dioxide, a substance that contributes to global warming process. Made out of microbial carbonate precipitation, bio-bricks only need room temperature to “heal.”
Researchers argue that the problem is the unpleasant odor the process releases. "Say you had a pet and it peed in the corner, and you have that strong smell - that's ammonia being released. The process releases exactly the same type of substance,” explained the University of Cape Town teacher.
However, as the process produces extremely high pH that kills all types of pathogens and bacteria, the ammonia odor dissipates after 48 hours. Thus, bio-bricks do not pose any threat to health - nor to nostrils.
Published 19 December 2018