Want to Fertilize Your Garden? Try Recycled Urine

Though it sounds disgusting, a new initiative in Amsterdam is part of an effort to find natural alternatives to traditional fertilizer.

(Photo: Allan Baxter/Getty Images)

Nov 27, 2013· 2 MIN READ
A Bay Area native, Andri Antoniades has previously worked as a fashion industry journalist and a medical writer.

The next time your vegetable garden needs perking up you may want to consider a rather unorthodox fertilizer—recycled human urine. Reprocessed wastewater has over the years increasingly gained traction as a sustainable fertilizer: one that promotes plant growth and could, in large-scale applications, save energy on sewage disposal.

That’s the rationale behind Green Urine, a new pee-recycling program in Amsterdam. Run by Waternet, the city’s utility company, the initiative is collecting urine from residents to fertilize rooftops across the city.

Sparing its employees the awkwardness of going door-to-door asking residents to pee in a cup, Waternet instead has set up rows of temporary urinals in one of the city’s public squares. After it’s collected, the urine will be processed to extract its phosphates, turning them into struvite, a powdery substance used as fertilizer. That struvite will later be spread across several acres of rooftop gardens in the city.

“It is totally possible to use human urine as a fertilizer instead of industrial fertilizer,” environmental scientist Helvi Heinonen-Tanski told Scientific American. In addition to making agricultural methods more sustainable, urine-based fertilizer could help boost food production and heighten sanitation in developing countries, particularly in small communities where wastewater treatment simply isn’t available.

Traditional phosphate fertilizers have been used since the 1800s, but our global dependence on them to grow our food has some concerned we’re depleting the planet’s phosphorus supplies—a concern that could be alleviated by sourcing the compound from human urine.

Not everyone agrees on that point, however. Some argue we have about 300 years' worth of phosphorus in our reserves, while others say the planet could run out within the next century. If the latter is correct, that poses an obvious problem for our world’s food supplies.

The Green Urine campaign is also a test case for the sewage treatment plant Waternet is set to open next year. Featuring a dedicated collection point for human wastewater, officials at the facility have set a goal of collecting urine samples from 1 million Amsterdam residents in the hopes of producing 1 million tons of fertilizer annually.

Waternet is just the latest group to jump on the pee-cycling bandwagon. In 2007, researchers in Finland actually did go door-to-door collecting urine from locals. That untreated wastewater was used to successfully fertilize small crops of vegetables such as cucumbers and cabbage—all of which the researchers reported tasted delicious.

Earlier this year, chemical engineers at the University of Florida joined the pro-pee cause. They successfully tested methods for extracting phosphorus from urine before it had a chance to hit the sewage system, where it can become diluted and more difficult to collect. Their goal was to inspire the use of diverting systems, such as waterless urinals and composting toilets, both of which could cut down on water usage and simplify waste streams.

Fertilizing plants by peeing on them is a centuries-old tradition, though in our modern minds, the very idea can seem...well, gross. But it actually isn’t. As a fertilizer, Scientific American writes, urine poses no health risk, and wastewater is often recycled into clean drinking water.

Still, getting past the ick factor might be difficult for some.

But considering our surging global population and the crucial need to find sustainable methods for supporting it, we might eventually have no choice.