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.