‘This is not a hippy thing’: the startup recycling urine to make natural fertiliser

As recent conflicts expose vulnerability of fertiliser markets and its effect on food security, VunaNexus offers an alternative

When staff answer the call of nature at the European Space Agency’s headquarters in Paris, their urine is not simply flushed away – it is turned into something much more useful. While urine-diverting toilets are often associated with smelly festival loos, there is nothing bohemian about recycling nutrients from human pee, said David de Chambrier, the chief executive of VunaNexus.

The process isn’t so different from recovering minerals in used electronics.

“Urine is a very concentrated resource. This is not a hippy thing to do; we are recycling minerals,” he said. Similarly to batteries, which should not be thrown in the bin to be recycled, “separating the urine at the source makes its treatment way easier”.

Special toilets that look like normal facilities send the separated liquid, without diluting it with water, down a piping system into a small treatment plant in the basement of the building.

There, the urine goes through a series of tanks that remove micropollutants, such as antibiotics, and concentrate valuable nutrients such as nitrogen and phosphorus that are essential for plant growth. The liquid is then pasteurised at 90C, killing any potential viruses and other pathogens. The distilled water is separated and reinjected into the flushing system before a liquid fertiliser called Aurin comes out on the other side.

VunaNexus, the Swiss startup behind the technology, says Aurin is the only mineral fertiliser made entirely of human urine that is certified on the market. It is approved for use on all plants by the Swiss and French authorities and is sold to farmers, for use in gardens and on house plants and is being tested by city authorities in Paris, Lausanne and Zurich.

Until the start of Russia’s war in Ukraine in 2022, which sentfertiliser prices soaring, “we were still seen as a bit hippy”, said de Chambrier, who leads VunaNexus with his sister Nadège de Chambrier, an environmental engineer and the company’s chief technical officer. But that has now changed.

The chokehold on the strait of Hormuz, through which about a third of the global trade in raw materials for fertilisers – and a fifth of shipments of the liquified fossil gas required to make them – passes, has acutely exposed the vulnerability of the fertiliser market and spurred renewed interest in alternatives.

The UN has said 45 million people are at risk of acute hunger because of the conflict in the Middle East as fertiliser prices soar and the supply shock threatens food security in some of the world’s poorest countries.

Today, the VunaNexus system is installed in several large commercial and residential buildings including one of Switzerland’s largest private banks in Geneva, recycling about 3m litres of urine a year. The technology is being rolled out across a newly developed eco neighbourhood in Paris, which will be the biggest project of its kind in Europe.

“If we were to recycle all the urine of people in Europe, I think we could cover around 30% of the nitrogen need,” said de Chambrier. That’s not enough to transform the fertiliser market but it provides an alternative to increase the resilience of water treatment systems in dense urban areas and reduce fertiliser’s environmental impact, he said.

Far from wealthy European cities, the company was born out of a pioneering research project in South Africa more than a decade ago, which aimed to develop an affordable sanitation system that could produce urine-based fertiliser. It was called Vuna, which stands for Valorisation of Urine Nutrients in Africa and means “harvest” in the local isiZulu language.

More than 80,000 urine-diverting dry toilets were installed on the outskirts of Durban. The project, which was co-led by the Swiss water research institute Eawag, piloted a scheme to collect the urine, treat it and concentrate its nutrients into a natural fertiliser that could be used by local farmers.

The fertiliser was tested on maize crops, demonstrating that the technology worked, but the logistical costs of transporting, storing and processing the urine made the project unviable at scale.

Making the economics work remains a major challenge, even in Switzerland. On a small treatment site, the cost of producing one kilogram of nitrogen from urine is 40 to 50 times that of synthetic fertiliser, said de Chambrier.

To become competitive on the agricultural market, VunaNexus needs to scale its fertiliser production and should get paid for the wastewater treatment service it provides, he suggested.

In Durban, researchers and NGOs are still working on finding ways to deliver improved urban sanitation that can produce fertilisers.

One project aims to establish a urine collection system from low-tech street-level urinals installed in a central area of Durban where thousands of informal workers earn a living as street vendors and in the district’s markets without adequate sanitation. An old water treatment plant once used in the Vuna project is being rehabilitated to turn the collected urine into fertiliser.

Richard Dobson, a co-founder of the NGO Asiye eTafuleni which works alongside informal workers using public spaces for their livelihoods, said: “We need to reconceive what is deemed waste and how you can turn a public nuisance into an urban good.”

The project, he said, would create “a nice closed loop”. Collecting the urine of people trading in public spaces and turning it into fertiliser could benefit the farmers growing the vegetables being sold on the street – a cycle that could create dignified job opportunities and reinject economic benefits into the local economy, he said.

Meanwhile, Maano Tshimange, a researcher at the University of Surrey, who grew up without a toilet in a rural area in one of South Africa’s poorest provinces, is studying how to improve the performance of an energy-efficient technique to concentrate nutrients from urine using a membrane system.

Tshimange, whose family used urine to fertilise their crops, said the technology makes it possible to produce urine-based fertiliser at scale, but more work was needed to convince governments and farmers that it is safe to do so.

“I still believe that in rural areas where people don’t have access to fertilisers I can make a difference in raising awareness that urine isn’t waste but a valuable resource,” she said.

Ultimately, VunaNexus hopes to turn Aurin into a fertiliser standard that is cheap enough to be produced in other parts of the world, including in Durban. “Our goal as a company is to bring this technology back where it came from,” said de Chambrier.