Human urine could be an effective and less polluting crop fertiliser

French researchers think they may have found a unique natural alternative to chemical fertilisers. Their discovery reduces environmental pollution and helps to feed a growing global population, all thanks to an unexpected ingredient - human urine.

Synthetic nitrogen fertilisers boost agricultural production but if used in excess, they pollute the environment. Their prices are also soaring, especially now with the war in Ukraine. It has left scientists searching elsewhere for a solution to this combination of crises.

"Our urine", say researcher Fabien Esculier.

To grow, "plants need nutrients, nitrogen, phosphorus and potassium," explains the engineer and coordinator of the OCAPI research program. When we eat, we ingest these nutrients before "excrete them, mostly through urine."

For a long time, urban excrement was used in agricultural fields, before being replaced by chemical fertilisers.

But when these nutrients are released in large quantities into rivers, they are one of the main sources of pollution.

Separating and collecting the urine at the source means rethinking toilets, the wastewater collection network - and overcoming certain preconceived ideas.

The separation of urine from toilets was first tested in Swedish eco-villages in the early 1990s, then in Switzerland or Germany. Experiments are now also being carried out in the United States, South Africa, Ethiopia, India and Mexico.

In France, projects are emerging in Dol-de-Bretagne, Paris, Montpellier.

The first generation of toilets with a urine separator were considered impractical and unsightly. A new model, however, developed by the Swiss company Laufen with Eawag has got good reviews.

Fabien Gandossi, who owns the 211 restaurant in Paris, equipped his establishment