Why Is Amsterdam Seeking Urine Donations For Its Green Roofs?

CREDIT: Shutterstock

Looking for a fun fact to bring up at the Thanksgiving Day table? Well look no further, because the ever-eccentric city of Amsterdam has got you covered.

As reported by Treehugger, Amsterdam’s water utility, Waternet, has begun collecting pee from public urinals in order to fertilize roofs of buildings that are covered with vegetation. These appropriately-named “green roofs” generally serve to absorb excess stormwater, which can be one of the biggest sources of excess runoff in a metropolitan area.

This is usually due to the fact that cities have a great deal of pavement and little ground to absorb rainfall, so sewer systems can be overwhelmed by rain, triggering the discharge of polluted runoff from streets mixed with untreated sewage into the nearest body of water. Green roofs help to mitigate that.

Amsterdam’s green roofs also help clean the city air, and provide habitats for birds and insects.

But why pee on this?

Might it be hard for women to pee in these?

Might it be hard for women to pee in these?

CREDIT: Chris Toala Olivares via

The answer is that urine contains phosphorus, a mineral that is essential for healthy plant life but that some scientists say could be depleted within the century. Though other scientists disagree, Amsterdam nonetheless wants to be prepared — the city already has tall, gray, plastic public urinals all over the city.

“Even if there isn’t a looming shortage, cities can still look at ways to extract more value from urine,” a report in UBM Future Cities noted. “It may also help protect them against fluctuating fertilizer prices. This is why Waternet is looking to extract more phosphates from urine and sewage.”

UBM’s report said that construction for a urine processing plant began in September and is set to open next year. If the city is able to collect urine from 1 million people, it could produce 1,000 tons of fertilizer annually, UBM said.