Human urine is being transformed into certified fertiliser at the European Space Agency’s headquarters in Paris, where staff urinate into special toilets that divert the liquid away from the main sewer system. The resulting product – a mineral fertiliser called Aurin – is the only one of its kind made entirely from human urine that has been certified for sale on the open market. “This is not a hippy thing to do; we are recycling minerals,” said David de Chambrier, chief executive of the Swiss startup VunaNexus, which developed the technology. He compared the process to recovering valuable materials from used electronics or batteries: “Separating the urine at the source makes its treatment way easier.”
Inside the Paris basement treatment plant
At the ESA building, the urine‑diverting toilets look entirely normal but send concentrated urine – undiluted by flush water – through a dedicated pipe system into a small treatment plant in the basement. There, the liquid passes through a series of biological and physical tanks that remove micropollutants such as antibiotics and concentrate the nutrients essential for plant growth, notably nitrogen and phosphorus, along with potassium and trace elements including iron, zinc and boron. The treated liquid is then pasteurised at 90°C to kill any viruses and pathogens. Distilled water separated during the process is reinjected into the flushing system, while the remaining concentrate becomes Aurin.
Odour is eliminated within five to ten days through a bacterial process called nitrification, which converts ammonium into nitrate. Visitors to VunaNexus installations have commented on the lack of smell even when large volumes are being processed. The energy required to recycle nitrogen using this method is comparable to the energy consumed by the conventional Haber‑Bosch process that produces synthetic nitrogen fertiliser from natural gas.
Aurin has been approved for use on all plants by Swiss and French authorities, and is also authorised in Liechtenstein and Austria. It is sold to farmers, gardeners and house‑plant owners, and is being trialled by city authorities in Paris, Lausanne and Zurich.
Geopolitical shocks reset the market
Until Russia’s full‑scale invasion of Ukraine in 2022 sent global fertiliser prices soaring, urine‑based products were still widely dismissed as a fringe idea. “We were still seen as a bit hippy,” de Chambrier recalled. That perception has shifted dramatically, not least because of the vulnerability of the conventional fertiliser trade. The Strait of Hormuz – through which roughly a third of the world’s seaborne fertiliser raw materials and a fifth of the liquefied natural gas needed to make them pass – has become a critical chokepoint. The conflict in the Middle East has exposed the fragility of supply chains, and the United Nations has warned that 45 million people are at risk of acute hunger as fertiliser prices spike and threaten food security in the poorest, most import‑dependent countries.
VunaNexus now has its system installed in several large commercial and residential buildings, including one of Switzerland’s largest private banks in Geneva. Together, these sites recycle about three million litres of urine a year. A newly developed eco‑neighbourhood in Paris is rolling out the technology in what will be the biggest project of its kind in Europe. De Chambrier estimates that recycling all the urine produced in Europe could cover roughly 30% of the continent’s nitrogen fertiliser needs – not enough to transform the market on its own, but a meaningful alternative that improves the resilience of urban water treatment and cuts the environmental footprint of fertiliser.
Roots in a South African research project
The company’s technology did not originate in Europe. It grew out of the Vuna project, launched more than a decade ago in South Africa. The name stands for “Valorisation of Urine Nutrients in Africa” and also means “harvest” in isiZulu. The project, co‑led by the Swiss Federal Institute of Aquatic Science and Technology (Eawag), aimed to develop an affordable sanitation system that could produce fertiliser from urine. More than 80,000 urine‑diverting dry toilets were installed on the outskirts of Durban. A pilot scheme collected the urine, treated it and concentrated the nutrients into a fertiliser that was tested on local maize crops. The trials proved the technology worked, but the project hit a serious obstacle: the logistical costs of transporting, storing and processing the urine made the operation unviable at scale. User acceptance and a clear understanding of the rationale behind urine diversion also proved difficult.
The economic challenge – and the path to scale
Making urine‑based fertiliser economically competitive remains the central challenge. On a small treatment site, de Chambrier said, the cost of producing one kilogram of nitrogen from urine is 40 to 50 times that of synthetic fertiliser. VunaNexus needs to scale up its production and, crucially, to be paid for the wastewater treatment service it provides. Under its current model, building owners can generate revenue by reselling the fertiliser and benefit from reduced carbon dioxide emissions, while the company manages the treatment, maintenance and logistics. The target return on investment is 15 years.
The company is also involved in pilot projects beyond western Europe – including the P2Green initiative in Hannover, Germany, and the ZirkulierBAR project in the Berlin region – and has begun optimising the technology for animal urine on Swiss swine farms, treating roughly 3,000 litres a day. VunaNexus was founded in 2022, building on a sister company that had focused on decentralised sanitation since 2016, and has received funding through a MassChallenge grant.
Durban’s ongoing efforts – and a vision for a closed loop
Back in Durban, researchers and NGOs are still working to turn the original Vuna concept into a practical, large‑scale system. One project aims to install low‑tech street‑level urinals in a central district where thousands of informal workers – street vendors and market traders – have no adequate sanitation. An old water treatment plant once used in the Vuna project is being rehabilitated to process the collected urine into fertiliser. Richard Dobson, a co‑founder of the NGO Asiye eTafuleni, which works alongside informal traders, said: “We need to reconceive what is deemed waste and how you can turn a public nuisance into an urban good.” He described the project as “a nice closed loop”: urine collected from people trading in public spaces could be turned into fertiliser for the farmers who grow the vegetables sold on the same streets, creating dignified jobs and circulating economic benefits locally.
Meanwhile, Maano Tshimange, a researcher at the University of Surrey, is studying how to improve the performance of an energy‑efficient membrane system that concentrates nutrients from urine. She grew up without a toilet in a rural area of one of South Africa’s poorest provinces, where her family used urine to fertilise their crops. She said the technology can produce urine‑based fertiliser at scale, “but more work was needed to convince governments and farmers that it is safe to do so”. She added: “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.”
VunaNexus’s ultimate ambition is to turn Aurin into a fertiliser standard 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.
