University students in South Africa have developed a way to create environmentally friendly bricks using human urine.
Urine From Men's Toilets
The engineering students at the University of Cape Town involved in the project first gathered urine from men's toilets. They then combined the urine with sand and bacteria in a process known as microbial carbonate precipitation.
The bacteria produce urase, an enzyme that breaks down urea in urine, forming calcium carbonate that then binds the sand into bricks.
Strength Of Bio-bricks Is Scalable
Dyllon Randall, the lead supervisor of the students, explained that the process is essentially the same as how corals are made in the ocean. The strength of the bio-bricks, however, can be scaled up and down depending on how the bacteria are allowed to grow.
Randall said that the longer the bacteria is allowed to make the cement, the stronger the product becomes.
He also said that when the process was started, they only achieved the same compressibility strength as 40 percent of a limestone brick.
They eventually doubled the strength by just changing the materials that they put in the mold and allowing the bacteria to cement the particles for a longer time.
The bricks can now be made to be as hard as a limestone, albeit the strength of these bricks would depend on the needs of the client.
"If a client wanted a brick stronger than a 40 percent limestone brick, you would allow the bacteria to make the solid stronger by 'growing' it for longer," said Randall.
"The longer you allow the little bacteria to make the cement, the stronger the product is going to be. We can optimise that process."
Process Produces Zero Waste
Most of the bricks produced worldwide are still made using the rudimentary process that involved getting the materials kiln-fired at temperatures around 1,400 C, which produces copious amounts of carbon dioxide.
The process involving the bio-bricks, on the other hand, produces zero waste because the by-products are nitrogen and potassium, elements that are used in commercial fertilizers.