Human urine – often flushed away without thought – could be key to making agriculture and wastewater treatment more sustainable and energy efficient, according to new research from the University of Surrey.

Although urine only makes up around one per cent of wastewater, it contains the majority of essential nutrients for plants, including nitrogen, phosphorus and potassium.

In a study published in the Journal of Environmental Chemical Engineering, researchers looked into how these nutrients can be recovered and reused by concentrating urine into a fertiliser-rich stream. Using a low-energy process known as forward osmosis, the team were able to remove water and retain high levels of nutrients without the energy demands of conventional wastewater treatment technologies. The approach could reduce the burden on treatment plants while supporting more sustainable fertiliser production.

Dr Siddharth Gadkari, Lecturer in Chemical Process Engineering at the University of Surrey and lead author of the study, said:

“It is strange to say, but it has the added benefit of being true – our pee is an underutilised resource. Even though it contains the key nutrients we need for agriculture, we currently treat it as waste. Our research shows that with the right treatment approach, we can recover these nutrients efficiently while reducing the energy demands of wastewater treatment.”

A major challenge for membrane-based systems is membrane fouling – where biological and organic material builds up on the surface over time and reduces performance. The study provides one of the first detailed insights into how human urine behaves under repeated operation, showing how different conditions affect fouling, system efficiency and cleaning.

The research team found that simple pre-treatment steps, such as filtration, can significantly improve performance, while most fouling can be reversed through cleaning – making the system more viable for long-term use.

Dr Gadkari added:

“What is particularly exciting is that we have demonstrated how this system behaves under realistic conditions using real human urine. If we can effectively manage fouling, this technology can move much closer to practical, long-term use.”

The work was carried out in collaboration with the University of KwaZulu-Natal in South Africa, where source-separated urine systems are already being explored at scale.

Researchers believe that their work could help reduce reliance on energy-intensive fertiliser production, lower carbon emissions and support more sustainable water and nutrient management worldwide.