Urine Collection Beats Composting Toilets for Nutrient Recycling
April 2, 2014
Human urine collection and use provides a better way to recycle nutrients than use of composting toilets.
Just when you thought it was safe to enjoy this blog over a cup of coffee here’s an article on…urine?
Let me explain.
Urine is a largely sterile, nutrient-rich resource that can be used in fertilizing plants. In fact, according to the Rich Earth Institute, the urine from one adult in a year can provide the fertilizer for over 300 pounds of wheat—enough for nearly a loaf of bread per day.
The Rich Earth Institute is a Brattleboro, Vermont-based organization that’s at the leading edge of the little-known practice of urine collection and use—something that’s emerging in Sweden and a few other places. This past Friday night roughly 200 people gathered at the Strolling of the Heifers’ River Garden in downtown Brattleboro to hear Abe Noe-Hays and Kim Nace from the Rich Earth Institute, along with a New York City comedian/activist, Shawn Shafner, discuss the idea.
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Mixing waste and potable water
With conventional practice, human waste (urine and fecal matter) is mixed with large quantities of potable water and flushed down toilets. From there, it typically flows to municipal wastewater treatment plants where energy- and chemical-intensive processes use bacteria to break down organic wastes, separate out biosolids, kill pathogens, and release that water into rivers or aquifers.
For those living in rural areas not served by a municipal sewer system, that wastewater flows into septic tanks where solids settle out and the effluent then flows into the soil through leach fields—in most cases with most of the nutrients in that waste filtering down into the underground aquifers. I learned when researching onsite wastewater disposal years ago for Environmental Building News (see On-site Wastewater Treatment: Alternatives Offer Better Groundwater Protection, as well as the more recent Waste Water, Want Water) that the aquifers under rural New England towns almost always have nitrate levels that significantly exceed federal drinking water standards.
At the same time, in the chemical industry, tremendous quantities of natural gas are used in the Haber-Bosch process (invented in 1915) to extract nitrogen from the atmosphere, which is made up of roughly 78% nitrogen gas (N2), to produce ammonia fertilizer, the mainstay of commercial agriculture.
Utilizing human urine
When most people think of creating fertilizer from animal waste, they think of manure. Composted cow manure, for example, is widely sold in garden centers. But there are actually far more nutrients in urine than in fecal matter.
In human waste, 88% of the nitrogen is contained in the urine, along with 66% of the phosphorous, according to Swedish research, while nearly all of the hazards—including bacterial pathogens—are contained in the fecal matter.
The idea that the Rich Earth Institute has been advancing for the past several years is to collect human urine, sanitize that urine to kill any bacteria that may be in it (from urinary tract infections, for example, or fecal contamination), and then apply it on fields as a fertilizer.
Abe Noe-Hays (who used to work for our company, BuildingGreen!), has been leading the charge with this idea in the U.S. The Rich Earth Institute secured funding from the U.S. Department of Agriculture, through the Sustainable Agriculture Research and Education (SARE) program to study urine collection and use as fertilizer, and the Institute is into its second year of this study.
Specialized urine-separating flush toilets are available in Scandinavian countries with front chambers for capturing urine (GreenSpec lists two. Abe Noe-Hays manufacturers a urine-separating composting toilet (listed in GreenSpec), and the Institute provides toilet insets for urine collection. On a larger scale, collection of urine from men’s rooms that have waterless urinals is particularly easy.
With the help of Best Septic Service in Brattleboro, the Institute collected 3,000 gallons of urine from over 170 participants in 2013.
According to most experts, simply storing urine for a while in a sealed container is enough to kill bacteria, due to the high alkalinity and ammonia from the urine. But the Rich Earth Institute is experimenting with faster pasteurization systems that heat the urine (including with solar systems that circulate solar-heated fluid through heat exchangers in the urine tanks). They are also testing various strategies for controlling odor—likely the biggest hurdle we face with urine collection and use.
In Sweden urine is being applied on food crops, but to date, with USDA support and permits from the State of Vermont, the Rich Earth Institute has stuck with less controversial applications on non-food crops—specifically hay fields.
Initial results last year with undiluted urine and dilution rates of 1:1 and 3:1, dramatic improvement in hay production was seen (see photo).
Because urine may contain pharmaceuticals being filtered from the body by our kidneys, there is an important question about whether that could pose a problem for use of urine as fertilizer. This year, the Institute will begin an EPA-funded study to test whether residual pharmaceuticals in urine are taken up by vegetables grown on experimental plots.
Better than composting toilets?
I have long been a fan of composting toilets. I like the idea of not mixing human waste with potable water, and I’ve always felt that flushing away the nutrients in human waste was a lost opportunity. But when I learned about urine separation and use (believe it or not in a luncheon presentation on the topic at a conference in Houston, Texas in 2009), I began to see the benefits of urine separation over standard composting toilets.
With standard composting toilets, most of the nitrogen in the waste ends up being volatized as either nitrogen gas or ammonia—and lost into the atmosphere. With urine collection and use, the nutrients aren’t lost; they are recycled in a sustainable nutrient cycle. That's part of why EBN has called urine separation "the next wave of ecological wastewater management."
This is something we’re considering for Leonard Farm, though we have not installed such a system yet. For more information or to participate in ongoing studies, contact the Rich Earth Institute.
Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.