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Fertilising crops with pee? Yes we can.

SCIENCE

It’s no great secret human urine is full of useful chemicals. People have for some time used it to fertilise citrus trees in particular and veggie gardens in general. Small scale . . . so far. However, that could be about to change. What’s being dreamed up on a quiet industrial estate in the south of France is big. The entrepreneurs behind Toopi are calling for a “peevolution”: a wholesale reassessment of how we think about urine. Far from flushing it down the toilet and spending billions treating it, Toopi is part of a movement that hails pee as an extremely valuable resource — if only they can get enough of it!


It all began just two years ago, reports Wired, when Matthieu Préel, a frustrated portaloo manager, was venting to a friend about how difficult it was disposing of the human urine he had on his hands. “He was telling me how annoying it was to have to pay all this money to dispose of all this pee,” says Michael Roes, Toopi’s co-founder. “[Préel] said to me, ‘Do you have an idea for something we could do with it?’”


Roes knew exactly what he could do with all that excess urine. As manager of a fertiliser company, he was well aware it could be used to feed and nourish plants. The problem was you needed a lot of pee. Urine contains just a fifth of the nitrogen found in your average bottle of nursery fertiliser, and less than five percent each of the potassium and phosphorus, according to a chemical analysis by Fabien Esculier, a researcher at the Ecole des Ponts ParisTech engineering school.

Roes’ challenge was to turn urine into a fertiliser that could compete with the industrial version. He began mixing urine with bacteria he suspected would boost the levels of nitrogen, phosphorus and potassium from the pee that plants could use. “It seemed to work,” he says.


Pee, it turned out, was a great culture for these microorganisms. The result was a kind of super-charged urine that, according to early testing, compares well with chemical fertilisers, litre-for-litre. Tests done in collaboration with the National School of Agricultural Engineering in Bordeaux found that Toopi’s fertiliser helped corn plants grow 60–110 percent more compared to a mineral fertiliser.


Roes eventually wants to process one or two million litres a year, in a process that involves warming the urine up in metal vats and shaking it around to help the bacteria grow. “Winemakers add bacteria to grape juice to transform it into something else. We’re doing the same thing — but with urine,” he says.

Turning urine into fertiliser isn’t just about dealing better with a ‘waste’ product, it could help relieve pressure on the environment, too. Unlocking the plant-feeding potential of our urine could reduce our reliance on synthetic fertilisers, which currently help produce food for at least half of the world’s population. However, nitrogen applied to fields often ends up in waterways, feeding algal blooms — those vast stretches of algae that pollute lakes and rivers — by drastically cutting the water’s oxygen supply.

Synthetic fertilisers also require a lot of energy. “We’re talking about one or two percent of global energy use,” says Esculier. He also notes that urine would be a more reliable source of phosphorus, which is extracted from mines in China, Russia and the disputed Western Sahara. Rather than dig fertiliser out of the ground, why not switch to a source of phosphorus that's as abundant as we are?


Esculier and his colleagues have been testing a range of urine-based fertilisers, and although they’re yet to publish the results, he says most of them are as efficient as their chemical alternatives. However, run-off from urine-based fertilisers could also feed algal blooms. “In my view, it’s more about transforming agricultural practices and figuring out how urine could be used in new eco-farming methods,” he says.


Esculier is also preoccupied with redesigning sanitary systems to divert urine before it hits the drain. Each human produces more than 450 litres a year, the vast bulk of it flushed away with clean water. Modern toilets flush everything down together, making it impossible to separate pee from poo. Swedish companies began developing designs that separate the two in the 1990s, and the German-made NoMix toilet followed around the turn of the millennium. Men didn’t like having to sit down to get the angle right, though, and the company eventually stopped making them.

Could the urine-diverting loo make a major comeback? Perhaps. Fancy Swiss bathroom brand Laufen gave the idea a swish update last year. “I actually think it’s better than a normal toilet,” says Kai Udert, a veteran of human waste research whose institute, EAWAG, helped out with the design.


Toopi’s plans don’t necessarily depend on mass uptake of separating loos; they could source the pee from urinals. But even then, they’d need a huge quantity to produce at scale. The company is in talks with medical labs, festivals and construction companies that have portaloos on their building sites. Most enticing of all is a potential partnership with the Stade de France, home of the national football and rugby teams. The stadium seats more than 80,000 fans, most of whom visit the bathroom at least once during their visit!


Toopi has just raised €1 million in its first funding round and is developing five different liquid fertilisers that can be applied using existing farming methods. Roes says they’re cheaper to use; the starter fertiliser for new crops costs about 20% less than the chemical version. Distributors have “several million litres” on pre-order, according to the company.


Currently, though, they’re producing virtually nothing. Toopi, first, has to submit its fertilisers to rigorous testing. “France has some of the toughest regulations on fertilisers, so it isn’t easy,” said Roes. “But that means once French authorities have given us the go-ahead, the product would be pretty much ready to go worldwide.” Adding weight to their campaign, in January, a study from the University of Michigan determined that urine can be safely used as a fertiliser without fear it might fuel the spread of antibacterial resistance, a previous concern.


Regardless of whether or not Toopi ends up conquering the fertiliser market, Roes remains convinced our future lies in making much better use of our pee. “The world is already running out of clean water,” he said. “And if water’s in short supply, I think we’d rather drink it than flush it down the toilet.”


If we can unlock the plant-feeding potential of our urine, it could reduce our reliance on synthetic fertilisers, which currently help produce food for at least half of the world’s population.

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