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The so-called biological bricks are made from human urine from men's toilets, sand and bacteria producing urase. How are they better compared to limestone bricks? ( pixabay )
Students in South Africa have developed a way to create bricks that respect the environment using human urine.
Urine of men's toilets
Engineering students from the University of Cape Town participating in the project first collected urine from men's toilets. They then combined the urine with sand and bacteria in a process called microbial carbonate precipitation.
The bacteria produce the urase, an enzyme that breaks down urea in the urine, forming calcium carbonate that then binds the sand to the bricks.
The strength of bio-bricks is evolutionary
Dyllon Randall, the senior student supervisor, explained that the process is essentially the same as that used for making corals in the ocean. The strength of biological bricks, however, can be increased and reduced depending on how bacteria are allowed to grow.
Randall said that the longer the bacteria are allowed to manufacture the cement, the stronger the product becomes.
He also said that when the process was launched, they did not achieve the same resistance to compressibility as 40% of a limestone brick.
They eventually doubled the resistance by simply changing the materials they put in the mold and allowing the bacteria to stick the particles longer.
Bricks can now be as hard as limestone, although their strength depends on customer needs.
"If a customer wanted a stronger brick than a 40% limestone brick, you would allow bacteria to make the solid stronger by" developing "it longer," Randall said.
"The more you let the little bacteria make the cement, the stronger the product, we can optimize that process."
The process produces no waste
Most of the bricks produced in the world are still produced using the rudimentary process of baking the materials in the oven at a temperature of about 1,400 C, which produces large amounts of carbon dioxide.
The process involving organic bricks, meanwhile, produces no waste as the byproducts are nitrogen and potassium, elements used in commercial fertilizers.
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