Fertilizer is made of nutrients like nitrogen and phosphorus. Chemical fertilizers require huge amounts of energy to produce. But there are other, natural and more readily available sources. 

The University of Michigan, with support from the National Science Foundation, is working at making our water cleaner, and our agriculture more sustainable, by capturing one of those sources, rather than flushing it down the toilet.

On a hot summer afternoon near Brattleboro, Vermont, farmer Dean Hamilton has fired up his tractor and is fertilizing his hay field — with human urine. 

It takes a bit of time to get used to, says environmental engineer Nancy Love.

“I’ve been surprised at how many people actually get beyond the giggle factor pretty quickly,” she said, “and are willing to listen.”

Fine-tuning the recycling

Rich Earth Institute, a nonprofit, is working with Love and her team. Abraham Noe-Hays says they are fine-tuning new methods to recycle urine into fertilizer.

“There’s a great quote by Buckminster Fuller about how pollution is nothing but the resources that we’re not harvesting, and that we allow them to disperse because we’ve been ignorant of their value,” he said.

Harvesting the resource of urine — which is, after all, full of the same nutrients as chemical fertilizer — will fix two problems at once: eliminate waste and create a natural fertilizer.

The Rich Earth Institute has been using urine as fertilizer since 2012. Kim Nace says they collect about 26,000 liters a year, thanks to a loyal group of dedicated donors.

“We now have people who have some source-separating toilets in their homes. We also have people who have 55 gallon (200-liter) barrels where they collect and then we transport to our farms, and we’ve also got a large urine depot,” Nace said.

They pasteurize the urine to kill any microbes, and then it is applied directly onto hay fields like Hamilton’s.

Next level of project

Now that they’ve partnered with the University of Michigan, Love says they’re looking to take their project to the next level.

“There are three things we really are trying to do with the urine in this kind of next phase. We’re trying to concentrate it. We’re trying to apply technologies to reduce odor, and we’re trying to deal with trace contaminants like the pharmaceuticals,” she said.

Dealing with pharmaceuticals is an important issue. Heat urine kills germs but has no effect on chemicals like drugs that pass through our bodies.

“We know pharmaceuticals are a problem for aquatic organisms and water systems,” Love said. “It’s debatable about the impact on human health at very, very low levels. Independent of that, I think most people would prefer that they not be in their food.”

21st century infrastructure

For Love, this is all about redesigning our wastewater infrastructure for the 21st century. Too many nutrients in the water leads to poor water quality by causing hazardous algal blooms.

“Our water emissions are going into very sensitive water bodies that are vulnerable to these nutrient loads,” she said. “We need to change that dynamic. And if we can capture them and put them to a beneficial use, that’s what we’re trying to do.”

Their efforts could make agriculture greener and our waterways cleaner.
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