Pee for the Peonies - Modern Farmer

On a mission to transform human urine into an environmentally friendly fertilizer, researchers at the University of Michigan discovered the secret is a little age.

Urine is responsible for the majority of nitrogen and phosphorus—both common ingredients in fertilizers—that ends up in wastewater domestically. And at a time when fertilizer prices are skyrocketing and the global supply of phosphorus is running low, repurposing urine—or “pee-cycling”—offers an economical and environmentally minded solution.

Using urine as fertilizer is one way to address both the ways in which nutrients in the water systems are handled and the currently unsustainable nature of agricultural inputs, according to the research.

The first step to recycling urine into a usable fertilizer is removing bacteria and viruses that the urine may contain. That’s where the aging process comes in. Research found that letting collected samples sit for several months before use effectively eliminated any antibiotic-resistant DNA in the urine.

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“Based on our results, we think that microorganisms in the urine break down the extracellular DNA in the urine very quickly,” Krista Wigginton, a University of Michigan associate professor of civil and environmental engineering and corresponding author on a paper published in Environmental Science and Technology, said in a University of Michigan report. That means there is no concern of transferring resistance of bacteria into the environment when using the urine as a fertilizer.

In an effort to educate others about their finding, leaders of the research, including Wigginton and Nancy Love, also an environmental engineering professor, have been using the urine-turned-fertilizer to grow heirloom peonies at the university’s Nichols Arboretum.

Their research, funded by a $3-million grant from the National Science Foundation awarded in 2016, includes not only studying how to utilize urine as fertilizer but also gauging people’s reaction to the idea—hence the peony project.

Originally, the duo thought they’d get some adverse reaction to introducing people to their “putting pee on peonies” experiment, but Wigginton told Phys.org that they have mostly encountered understanding and support of the project. “In general, people think it’s funny at first, but then they understand why we’re doing it and they support it,” she said.

The two plan to be present at the peony beds on weekends for the next few months, informing visitors of their pee-cycling research.