The Michigan Engineer News Center

From pee to plant food: A visit to the Urine Depot

Michigan researchers in the Civil and Environmental Engineering Department are testing the urine, the soil around the plants, the groundwater beneath them, and the plants themselves. | Medium Read

It’s morning coffee time at Kim Nace and Mike Early’s cozy Vermont home that doubles as the headquarters of the Rich Earth Institute – a nonprofit that’s making food crop fertilizer out of human urine.

They hear someone pull up the driveway.

“We’ve got a donor!” Nace announces, and leaves to greet the visitor.

Outside, a young woman in a tank top lifts a five-gallon jug of amber liquid out of the back of her car. It’s about a week’s worth of urine from her household. She carries it over to the pumping station, opens the cap, sticks the hose in and turns on the machine. The pee gets sucked into a tarp-covered holding tank about the size of a washing machine.

This happens a couple times a day at the Urine Depot, as Nace calls it. More than 100 Brattleboro area volunteers have signed up to contribute to the institute’s mission of turning a waste product into an agricultural resource. It’s an effort Michigan Engineering researchers also have a hand in.

Michigan, Rich Earth and three other organizations are working together on an EPA-funded project to test whether the practice can be done safely, and more broadly. It’s the first large-scale attempt to do this in the United States.
Over the course of the next two years, disinfected urine or urine-derived products will be the nitrogen and phosphorus fertilizer on up to 100 square meters of lettuce and carrots at farms near Brattleboro. The approach has the potential to reduce the nitrogen pollution that creates “dead zones” where fish can’t live in rivers, lakes and marine environments like the Gulf of Mexico.

More directly, it aims to make both wastewater treatment and crop fertilization more efficient and environmentally friendly. Today, farmers typically use synthetic nitrogen and phosphorus fertilizers, which must be manufactured. Meanwhile, urine is chock-full of those substances. In the U.S., indoor plumbing mixes urine with feces and takes it to the treatment plant, where nitrogen and phosphorus can be removed (though not all plants have the technology to do that). It’s an energy-intensive cycle that the Rich Earth Institute and U-M researchers are aiming to break free of.

Michigan researchers in civil and environmental engineering are testing: the urine, the soil around the plants, the groundwater beneath them, and the plants themselves. They’re looking for bacteria, viruses and medications. All of those can be found in urine and the researchers want to see how they would move through their system and which treatment approaches could effectively removing them.

The depot deposits aren’t technically part of the EPA work. They’re being spread on hay for animal feed for a different but related study. The urine for the EPA project comes from broader “collection events” like parades and festivals. To gather urine there, the institute provides specially outfitted and sanitized port-a-potties that anyone can use. In that way, they get contributions from a broader sample of the population.

But the depot is, perhaps, where the biggest believers are. They’re the early adopters.

Hampton knows that peeing into a toilet insert and then funneling it into a jug might seem weird to some people. But to her, it makes sense.

She’s studying to be a dietician. So she finds herself thinking a lot about how the foods she eats changes her waste and how that, in turn, will change the fields.

“It’s like, ‘Okay, I’m really a part of this whole system,’” Hampton said.

“We’ve created this society where it gets flushed away and you don’t have to worry and everything has to be sparkly clean and smell nice.”

What she and others like her are doing is different.
“This is about talking about it and saving it and using it.”

At U-M, the project is led by Krista Wigginton, an assistant professor of civil and environmental engineering. Also participating are Nancy Love, a professor in the same department, and Rebecca Lahr, a postdoctoral researcher in the same department.

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