Can urine help save food production during crises?

One of the main components in conventional crop production is the use of imported mineral fertilisers. However, the climate crisis, higher prices and insecurity in import force us to rethink our ways to use mineral fertilisersand see other solutions.

Alkaline urine dehydration is a new technology under development by researchers at SLU to capture all the nutrients in urine without its water. The team at SLU is working to disrupt the way we manage wastewater and design sanitation systems. They believe that resources like urine should be separately collected, safely treated to produce fertilisers, and returned to farmland to close the nutrient loop in our food system. If implemented globally, such a system could reduce the transgression of the planetary boundary for nitrogen and phosphorus by 35% and 25%, respectively.

In terms of nutrients, urine contains more than 80% of the nitrogen and over half of the potassium and the phosphorus. In fact, urine produced by people worldwide contains enough nutrients to fertilise three-quarters of the food we eat.

– Drying is a simple operation that can be performed everywhere. An alkaline urine dryer can be put together in a few hours as it requires materials that are fairly easy to procure locally. By following a few simple steps, anyone can safely dry urine to produce a fertiliser. We have demonstrated that the technology works well in Sweden and Finland, but also in Bolivia. To perform alkaline dehydration, households need to have electricity supply, as fans need to be operated for ventilation. Our current focus is on reducing the energy demand for evaporating water as this is important to ensure wider acceptance and suitability of the technology in different contexts, says Prithvi Simha, researcher in the project.

– The global system of food production is the largest human influence today on the planet’s natural cycles of nitrogen and phosphorus, since we add these two elements as artificial fertilisers on farmland. So, most of the food we eat today is not farmed sustainably. But we can change this by switching over to human urine-based fertilisers, which would reduce our negative impact on the planetary boundaries and have the added benefit of improving the sustainability of our sanitation system. Dehydrated urine, for instance, can be used in urban farming to improve the resilience of local food systems, transported and applied on rural cropland, or used as a raw material by the fertiliser industry.  

With this technology it is possible to produce fertilisers without importing, which makes the production chain more resilient to disruptions, more sustainable with closed recycling loops, reduced use of fossil phosphorus, less transports, and reduced leakage of wastewater to nature.

- When a handful of countries that produce majority of the fertilisers also start banning fertiliser exports to safeguard their own food production, you soon start seeing fertiliser prices soar and food price inflation rise, says Prithvi. 

Watch a short video presenting the project. 

- But we can make local food production more resilient. The nutrients we need to grow our food are much closer to us than we realise – in our urine. If we collect and recycle all the urine we produce in Sweden today, we estimate that nearly one-quarter of the nitrogen and phosphorus fertilisers demand in agriculture can be met. The potential for substituting synthetic fertiliser with urine is much higher in countries with high population and low fertiliser use; for e.g., Uganda and Bolivia. 

- What we’re developing is a process that can convert urine to solid fertiliser pellets having the same composition as that of synthetic fertilisers on the market. Implementing this at scale would mean taking a significant step to make our food systems less vulnerable to global events and towards achieving fossil-free farming.