Could human urine help cut France's dependence on imported fertilisers?

France's cities produce millions of litres of urine every day. Most disappears into the sewer system. But some scientists are now saying what we flush away could help fertilise the country's fields – an eco-friendly way to reduce dependence on increasingly expensive and polluting imported fertilisers.

At a collection point in Châtillon, just south of Paris, Bruno Rakedjian unscrews the cap of a five-litre jerry can and inserts a plastic tube which then pumps the yellow liquid contents into a 150-litre container.

"Twenty of us in Châtillon are collecting urine at home," he says, pointing to a blue plastic funnel that makes peeing into the plastic container a straightforward affair.

Like the other members, he drops off his urine once a week when picking up organic vegetables supplied by the local farmer who collects the urine.

This small citizen-led initiative was started four years ago as part of a publicly funded project on using human waste in agriculture, run by research programme OCAPI.

"One person’s urine over the course of a year could fertilise 500 square metres of fields, and 25 million baguettes could be produced every day using the urine of everyone living in the Paris region," said Fabien Escudier, head of the OCAPI programme.

Escudier has been researching the use of human waste as fertiliser for more than a decade. Since instability in the Middle East pushed up the price of imported chemical fertilisers, there's growing interest in exploiting such homegrown alternatives.

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Double dependency

France is Europe's largest agricultural producer and relies heavily on fertilisers. Conventional French farmers spread an average of 170kg of nitrogen fertiliser per hectare of wheat, maize or sugar beet – 80 percent of which is imported.

Nitrogen fertiliser is produced using natural gas, largely from the Gulf States, while much of the phosphate used comes from Morocco and contains high levels of the toxic heavy metal cadmium, which has been linked to cancer.

"We have a double dependency," says microbiologist Marc-André Selosse.

With the Iran-US war and partial blockade of the Strait of Hormuz pushing up energy prices, Selosse argues that this dependence has become increasingly visible and "problematic".

But that's not the only cost. When excess fertiliser washes off fields into rivers and coastal waters, it can trigger algal blooms and water pollution.

"You lose money in tourism, in fish production and you have health issues for people [in the area]," Selosse says. "It's terribly costly, this story of mineral fertilisers."

Urine could provide a far cheaper, greener and healthier alternative.

"Every one of us produces around 11 grams of nitrogen and 0.7 grams of phosphorus in their urine every day," he says. "That's a resource."

Listen to this story on the Spotlight on France podcast:

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'The impact is huge'

Rakedjian joined the urine collection scheme four years ago through his local AMAP – a community-supported agriculture network linking consumers and organic farmers.

"I like to take action to protect the environment," he says. Since each flush of the loo uses 10 litres of water, peeing into a container instead also saves water, and money.

He says there's also a satisfying circular logic in closing the loop. "When we eat the vegetables, we produce urine. And then we give the urine back to agriculture."

His scheme supplies organic farmer Simon Ronceray with around 300 litres of urine each month.

"The project is far from some niche concern or crackpot idea," Ronceray told Reporterre magazine. "French farming depends on synthetic fertilisers derived from oil or highly polluting phosphate mines. Our urine can supply the necessary nitrogen, phosphorus and potassium, and completely free of charge."

Urine is already "nearly bacteria-free", says Selosse and studies have shown that if stored at 20C for at least six months, urine may be considered safe to use as a fertiliser for any crop.

After storage, Ronceray sprays it on the soil – around two litres per square metre.

"The quantity of urine collected is actually quite small compared with the needs of the partner farm," says Louise Raguet, a researcher with OCAPI and co-ordinator of the Chatillôn project. "But the social and cultural impact is huge."

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Urine-separating toilets

Since most of the urine currently collected in France is by companies that hire out dry toilets for events, Raguet says it's difficult to measure volumes, although "a few years ago we estimated that several hundred cubic metres were collected and used in agriculture".

The most high-profile urine collection project is at the headquarters of the European Space Agency in Paris, which has equipped its premises with urine-separating toilets.

In early 2027, around 600 homes will be equipped with these in a new sustainable housing development in Saint-Vincent-de-Paul in Paris's 14th arrondissement.

Urine is far less concentrated than traditional fertiliser so the volumes needed are far greater. But researchers believe it could nonetheless replace a meaningful share of current fertiliser use.

Raguet says estimates vary widely depending on how agriculture evolves.

"If we don't change agricultural practices, it's probably around 10 percent. But if we move towards agroecological systems, it could be 30 to 40 percent."

Selosse also emphasises that the lower amounts of energy needed to produce and transport urine-derived fertiliser would result in "three times less greenhouse effect".

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Agricultural regulations

France is still debating how urine-derived fertilisers could fit into existing agricultural regulations, particularly in organic farming.

Raguet says that at one point they believed they had secured permission for trials in organic agriculture.

"We had obtained a derogation but then there was an administrative muddle," she says, with different ministries unable to agree on the rules.

Ronceray said he couldn't risk losing his organic certification, so for the meantime he spreads the collected urine on his agroforestry hedgerows and in his own garden.

"You can clearly see a difference – the plants fertilised this way are more vigorous and grow much better," he said.

However, a number of conventional farmers, particularly in the Paris region, are experimenting with using it on cereal crops.

"Wheat, maize, colza – produce that will be cooked," Raguet says. "Urine is good at boosting growth in vegetables, but while we're still in the exploratory phase, most farmers prefer to start off with something like wheat or on non-edible crops."

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'The best of the past'

For centuries, both urine and excrement were collected and returned to farmland.

Microbiologist Selosse points to a system used in Lyon up until the late 19th century known as the merdoduc – "the word means pipelines for transporting shit".

Waste was collected in the city via 55km of pipelines and distributed to surrounding farmland. It was a source of paid work, but eventually disappeared as the city-wide sewage system was introduced and synthetic fertilisers became cheaper and easier to use.

Selosse says he's not proposing a return to medieval times, but a selective revival of old ideas combined with modern technology.

"It's taking the best of the past and the best of the future," he says.

Beyond citizen-led initiatives, Selosse says it's time to develop human waste collection on an industrial level.

"There are places in Paris where most of the urine is produced," he says, citing Charles de Gaulle Airport, the Louvre and Versailles. Once the toilets are installed, "it's easy to collect and to have pipelines for that".

His plan would involve compulsory screening of the urine to ensure it was safe to use, with collecting in places such as hospitals excluded.

Regulatory and logistical issues still have to be sorted out – not to mention public acceptance, since the idea of fertilising crops with human waste continues to provoke unease, even ridicule, he says.

And he has yet to win much political support.

"It looks to most [politicians] like a stupid thing of extreme ecologists, whereas it's a technical solution."

Listen to more on this subject on the Spotlight on France podcast.