In 2017, when Cape Town was facing Day Zero during a devastating drought, when the taps were expected to run dry and a city, a vast urban area, was on the brink of being declared a disaster zone, Dr Dyllon Randall thought about going to the toilet and saving the planet.
He came up with a simple and, yet, as most great ideas and solutions are, breakthrough idea. What about the water we waste in the necessary and frequent act of our ablutions? What about the water that is used to flush? What about the water that is used to clean that toilet? What about the human waste, the urine, that goes into that toilet? Surely, thought Dr Randall, a senior engineering lecturer specialising in water quality at the University of Cape Town, there was a way to use it instead of flushing it away?
There was. He and his colleagues developed a fertiliser-producing urinal in 2017. It allowed them not only to collect urine, but also to save water because the urinals were waterless. One ablution later and, within 30 seconds, solid fertiliser is produced.
“I often think about what else can we make from other waste streams and if we get that right, we’re constantly rethinking about waste streams as a resource instead of waste,” said Dr Randall. “This way, we will achieve a sustainable future much faster. If you think about it, nature actually produces no waste. All waste streams are completely recycled.”
The urinal is a 25-litre container with a funnel that screws on to the top, and has a splashback for added sanitation. The container can be removed to transport the urine to be processed. Calcium hydroxide, or lime, is added to the urine to create fertiliser.
“The purpose of the calcium hydroxide is actually the key to how the process works,” said Dr Randall. “So when you add calcium hydroxide, you increase the pH of the urine. When you urinate into the container, the pH of the urine increases to above 12. And this is key, because this is a really high pH and it does a number of things. It is the reason why we are able to recover 96 to 97% of the phosphates, because the high pH initiates the solid formation of your calcium phosphate and hence you can remove it from the urine.
“The high pH also kills pathogens or any harmful bacteria that might be present. So for example, your urine is generally sterile, but if someone is ill you might have things being passed through the urine. We found that just by increasing the pH of the urine, you can actually degrade the pharmaceuticals,” said Dr Randall.
This goes through a filtration system to remove the solid calcium phosphate. The then solid calcium phosphate is air dried and produces the first fertiliser, the solid fertiliser. Multiple options are open to the development and use of the liquid component. They could concentrate that liquid stream and produce a liquid fertiliser that is now rich in urea, which is a very good fertiliser and often used in agricultural fields.
“There are lots of synergies there. And it’s just by simply asking the question, what else can we make from urine?” said Dr Randall.
There is lots, as Dr Randall and his team discovered. The treatment process prevents the breakdown of another component in urine called urea. You can recover it as relatively pure urea crystals. This forms carbonate ions, and when it combines with calcium in the liquid, you form calcium carbonate which is a kind of cement. This is the same process that nature uses to create sea shells and coral reefs. The researchers use this bio-produced cement to also grow bio-bricks from human urine. See Dr Randall’s open lecture on this here: https://www.youtube.com/watch?v=ldl0-H-xP_s&feature=youtu.be
“Essentially what we do with the bio-brick process, we take loose material, so for the feasibility study, we just took normal sea sand, but you can use any loose aggregate. You could use building rubble, mining waste or whatever. And you colonise it with bacteria that produces an enzyme, which speeds up a reaction. In this case, the enzyme is called urease.”
In his lab at UCT Dr Randall has a transparent, Perspex-looking bio-brick mould that stands on little legs. It has plastic tubes running into it from a glass bottle that contains a golden liquid. From here comes the magic. The formation of a bio-brick from urine.
“Essentially, what it does is it starts gluing all the loose sand particles together with calcium carbonate, and eventually you'll get a solid forming of any shape you choose. If you do this in a shape of a bio-brick, then you're going to get a brick. If you do it in the shape of a column, you're going to get a column. You force the system to solidify over, typically, a period of four to six days,” said Dr Randall.
The world’s first bio-brick from urine solidifies at room temperature. Regular bricks need to be fired in a kiln that burns at a heat up to 1 400 degrees Celsius, a process the climate crisis does not need right now.
It feels like it’s just a beginning. Waste water, waste from human water. It’s an innovation that could make us think before flushing.
“If you think about the amount of water we use just to flush, we can use up to 30 to 40% of our daily water usage as an individual just to flush toilets. That’s shocking. And this is really great quality water. That’s water, you could literally drink but we are using it to flush away something that is valuable. Then we spend money and energy at water treatment plants to remove those components.
“But, if we upfront collected the urine, using no water, in waterless urinals or even innovative toilets, we can save 30 to 40% of our daily water usage. So the 60 to 80% of the nutrients that are there, which we can use to make fertilisers, which then can be used to grow food, rather than importing fertilisers, which many countries end up doing. I mean, everyone produces urine.”
Indeed they do.
See https://m.youtube.com/watch?feature=youtu.be&v=U7jm9RrezOo and visit www.jojo.co.za to access the podcast featuring Dr Randall. The 12-episode podcast series features stories about water across South Africa, and the water heroes and activists behind them. From phosphate mining in the Cape West Coast biosphere to protecting the Cape Flats aquifer to cleaning up Cape Town’s water canals. You can also search #ForWaterForLife on all the podcast channels: Iono, Spotify, Stitcher or Apple iTunes.
For more information visit www.jojo.co.za