What if human urine, effective and less polluting, replaced chemical fertilizers?

Will human urine soon replace chemical fertilizers? Many researchers and NGOs take the question seriously. According to them, it will reduce environmental pollution and feed an increasing number of the population. Synthetic nitrogen fertilizers enhance agricultural production. But when used in abundance, it pollutes the environment. Their prices are rising, even with the war in Ukraine, which has burdened farmers.

What to replace it? Paul, I’m answering to researchers including Fabien Escolier, who is considering reforming more sustainable diets. In order to grow, “plants need nutrients, nitrogen, phosphorous and potassium,” explains engineer and coordinator of the Ocapi (Improving City Carbon, Nitrogen, and Phosphorous Cycles) research program in France. When we eat, we take in these nutrients before we “excrete them, mostly via urine,” he continues.

Transcend Preconceptions

For a long time, urban waste was used in agricultural fields, before it was replaced by chemical fertilizers. But when these nutrients are discharged in very large quantities into rivers, they promote an explosion of green algae, for example, and represent “a major source of nutrient pollution,” asserts Julia Cavici, of the Rich Earth Institute, based in the USA.

Separating and collecting urine from the source requires rethinking the latrines and collection network and overcoming some preconceptions. Separation of urine from toilets was tested in Swedish eco-villages in the early 1990s, and then in Switzerland or Germany. Trials are taking place in the United States, South Africa, Ethiopia, India and Mexico. In France, projects are emerging. “It takes time to introduce environmental innovations, especially one as radical as urine separation,” says Tove Larsen, a researcher at the Swiss Federal School of Water Science and Technology (Eawag).

“We are beginning to understand how precious water is”

She explains that early generations of toilets with a urine separator, considered impractical and ugly, or a fear of bad odors might act as the brakes. The researcher hopes that the new model developed by the Swiss company Laufen together with Eawag will solve these difficulties. Fabien Gandousi owns Restaurant 211 in Paris, which is equipped with dry toilets where urine is collected. “We’ve got pretty positive feedback, people are a little surprised, but (..) they don’t see much difference compared to the traditional system.” “There are hurdles to overcome,” comments Marine Legrand, an anthropologist and member of the Okapi Network. But “we begin to understand how precious water is” and “defecating inside it becomes unacceptable.”

Are people still ready to eat urine-enriched foods? The study shows marked differences between countries. The acceptance rate is very high in China, France or Uganda, but low in Portugal or Jordan. “This topic touches intimacy,” analyzes Ghislain Mercier, of Paris and the Métropole Aménagement which is developing an eco-zone in Paris with 600 housing units and shops…Urine will be collected there and fertilize Parisian green spaces. According to him, there is great potential in offices and homes that are not connected to the sewage network or slums without sanitation facilities.

However, it is necessary to compel the population, to rethink the pipes, to counteract inappropriate legislation … Once the urine has been harvested, the urine must be transported to the fields, which is costly. Various technologies make it possible to reduce its volume and concentration of urea or even dry it. Rich Earth Institute is developing technology solutions to make spreading this fertilizer easy and inexpensive for farmers.

Since urine is not usually a major vector of disease, it does not require extensive processing for use in agriculture. The World Health Organization (WHO) recommends letting it rest. It is also possible to wear it. Urine is still struggling to establish itself as an alternative to synthetic fertilizers. But with rising gas prices and many countries wanting to bolster their food sovereignty, regarding the war in Ukraine, “economic restrictions will catch up to us faster than we thought and make the issue more heard,” comments Ghislan Mercier.

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