Noe-Hays was part of a study that looked at concentrations of pharmaceuticals in urine. Caffeine and ibuprofen were among the most common and abundant. After urine was applied to soil, however, the drug concentration in the crops was extremely low. According to the study, to consume the amount of caffeine in a cup of coffee from urine-fertilized produce, a person would have to eat a pound of the produce every day for about 2,000 years, Noe-Hays said.
Gardeners often use urine as fertilizer, and Noe-Hays said it works wonders from his personal experience. Noe-Hays said there is no necessary concentration of nutrients for urine to be used as fertilizer. The mass of its components is what matters. If pouring 1,000 gallons of urine on an acre, there are about 50 pounds of nitrogen added. Using a concentrate 10 times stronger than diluted urine, only 100 gallons would need to be applied to get the same impact, Noe-Hays said. “The hay doesn’t care whether you’re applying the concentrate or the dilute,” he continued. “It just matters how many total pounds of fertilizer it gets.”
For urine to be useful as fertilizer for something more than a personal garden, it’s helpful to take advantage of the ability to concentrate it. A spinoff of Rich Earth called Brightwater Tools is working on concentrating urine by freezing it, Noe-Hays said.
Freezing the water out of urine leaves behind the nutrients in a slurry that can be used onsite or shipped to a farm. Concentrating the urine makes the volume more manageable, particularly if urine-diverting toilets are used in a commercial or office building. Instead of needing multiple visits from urine-specific trucks to empty the tanks, the concentration hardware allows the urine to be sanitized, pasteurized, and freeze-concentrated on-site. In trials, the concentration levels reached a factor of 10, meaning trucks might come to collect every few months instead of every week.
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