This SA engineer turns urine into fertiliser – it may even be used to make jet fuel some day

Business Insider SA
Hlumelo Marepula. (Image: Supplied)
  • Hlumelo Marepula, a master's candidate at the University of Cape Town, turns human urine into fertiliser.
  • She is also exploring the feasibility of using urine to produce jet fuel with water as a by-product. 
  • The methods used in creating the human urine-derived fertiliser or urea are more sustainable than those used for synthetic urea, which is generally energy-intensive.
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Urine may be just waste that humans excrete daily, but to civil engineer Hlumelo Marepula, whose mission is to turn urine into fertiliser, it is a valuable commodity that both helps the planet and is cost-effective for farmers.

She recently bagged an award for producing a urea-ethanol solution that is recrystallised to make fertiliser or urea, and potentially diesel engine fluid with water as a by-product. 

Marepula, a master's candidate at the University of Cape Town (UCT), started exploring the feasibility of using human urine in jet fuel production under the supervision of associate professor Dyllon Randall from UCT's department of civil engineering and the Future Water Institute. But her research later evolved to focus on turning human urine into fertiliser. 

She then began exploiting urine for one of its most dominant components, urea. Urea is a raw material in producing various chemicals and is also a critical nitrogen-rich fertiliser.

The realisation that urea could also be used as a fertiliser, and not just jet fuel, catapulted Marepula to solving a problem in an entirely different industry where she could also address food insecurity issues in Africa, Marepula said. 

"… Especially in a continent like Africa where we have so much arable land and the synthetic version of urea, the one that's made in factories, uses a very energy-intensive process which is quite harmful and contributes a lot to climate change issues," she said. 

Marepula recently presented at the International Summit on Sustainable Development Goals (SDGs) in Africa, where she highlighted the need to come up with alternative methods of producing urea to reduce energy consumption, greenhouse gas emissions as well as costs and said using waste streams in a more circular economy approach is imperative.

"We're basically extracting and not giving back. When the reserves are finished… we won't have enough fossil fuels to make fertiliser to produce food, and we will end up with no food, and that's the long-term way of looking at it," Marepula told Business Insider South Africa. 

The urine was collected from waterless urinals that were installed in UCT bathrooms, where people donated their pee for the project. Once they were full, the urinals were taken to the lab, treated, and mixed with ethanol. 

"The vision is to try and retrofit sanitation in existing buildings so that the urine is no longer going to sewage waste streams and being taken to water treatment plants and have, for example, a separate piping system that diverts all the urine to a central system," she said. 

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