urine bricks

[Image above] Dyllon Randall, left, and his students Vukheta Mukhari and Suzanne Lambert show their bio-bricks made from human urine. Credit: Robyn Walker, University of Cape Town


Brick as a structural product is one of the oldest and most common building materials, and although there might be some debate as to whether clay bricks are a detriment to the environment or a sustainable construction material, the industry appears to be on board with improving its environmental footprint. In fact, the Brick Industry Association (BIA) advocates to “seek out innovative, environmentally friendly opportunities in the manufacturing process and for the end use of clay brick products.”

Perhaps the BIA might be interested in what researchers at the University of Cape Town are up to. Civil engineering students Suzanne Lambert and Vukheta Mukhari have created a bio-brick made out of human urine.

Yep, you read that right.

Led by senior lecturer in water quality engineering Dyllon Randall, the students combined sand, urine, and a bacteria that produces the enzyme urease to break down the urea that is present in urine. The reaction produces calcium carbonate, which the team used to bind the sand into a brick. It’s a similar process to the way nature makes seashells, according to a University of Cape Town news release.

What is significant about the bricks the team created and are currently testing is that they made the bricks at room temperature, as opposed to conventional bricks that need to be kiln-fired at 1400oC (2552oF), according to the release. The process alone could save a lot of CO2 from being released into the atmosphere. Additionally, the brick’s strength could be increased simply by letting the bacteria break down for a longer period of time.

“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,” Randall says in the release. “The longer you allow the little bacteria to make the cement, the stronger the product is going to be. We can optimise that process.”

But the success of the team’s research doesn’t end at the bio-brick. The process offers a bonus of nitrogen, phosphorous, and potassium—by-products that could be used in fertilizers for crops. Randall’s previous research has focused on recycling and separating urine to collect nutrients that would otherwise end up in the environment.

“A lot of the nutrients found in urine—so for example, the phosphorous, the nitrogen—If we allow that to enter the environment … we get the algae blooms that typically form in dams,” Randall explains in a video. “But if you were to recover those nutrients you could produce a fertilizer, and we actually are running out of natural phosphorous, for example. So if we were to recover this phosphorous from our urine, we can produce the fertilizer in a more sustainable way.”

Now that the process has been solidified, so to speak, the team is exploring ways of collecting, transporting, and recovering the useful components in urine to make the bricks and fertilizer.

The paper, published in Journal of Environmental Chemical Engineering, is “Microbial induced calcium carbonate precipitation at elevated pH values (>11) using Sporosarcina pasteurii” (DOI: 10.1016/j.jece.2018.07.046).

Watch the video below from Engineering.com to learn more about making bio-bricks from urine.

Credit: Engineering.com, YouTube