Urine collected from an outhouse behind Sudwerk Brewery Co. in Davis, California may help supply the next generation of fertilizers. By partnering with the craft brewery in the “sustainable fertilizer from urine project,” researchers from the University of California, Davis have developed the “pee hive,” a customized outhouse with a built-in pump, 250-gallon collection tank, and a urinal created from a sawed-off beer keg.
We excrete many of the nutrients we consume. These includes beneficial vitamins and minerals and the nutrients found in agricultural soils and fertilizers, which make their way into our food and drink. Salts, hormones, vitamins, and pharmaceuticals often end up flushed down the drain and diluted with waste water. With this in mind, UC Davis environmental engineer Harold Leverenz, sanitary engineer Russel Adams, and graduate student Jessica Hazard embarked on a journey to reclaim these nutrients from our waste.
“Our goal was to extract the primary agricultural nutrients — such as nitrogen and phosphorus — in a high-purity, pasteurized, safe, and concentrated form, with minimum energy input,” Leverenz told Digital Trends. Although Leverenz pointed out that urine is sometimes used as fertilizer in rural areas, this isn’t the most sanitary or socially acceptable practice in cities. So, the team looked to develop a compact, manageable, and automated technology that could be installed in urban areas.
A craft beer bar made for a good partner given the openness of many independent breweries to alternative methods, “not only in brewing, but also in environmental awareness and sustainability,” Leverenz said. From using recycled water to organic and local ingredients, craft breweries push the envelope on quality and sustainable practices. But it isn’t just the companies who have a sustainability-oriented outlook — Leverenz thinks craft beer drinkers tend to be curious and supportive of environmental initiatives as well.
Sudwerk and the UC Davis researchers decided to create an outhouse that complemented the bar’s aesthetic while living up to the project’s ethos. After considering a few different design concepts, they settled on a six-sided structure made of corrugated sheet metal — to match fermentation tanks — which had no construction waste and could be easily disassembled, moved, and reassembled by a single person. The outhouse’s hexagonal shape earned it its punny name — the pee hive.
About once a week, Leverenz and his team carefully load the 250-gallon collection tank onto a pickup truck and transport their haul to a treatment facility, where they can process some 100 gallons of urine per day in a three-step process that turns urea to ammonia, evaporates the ammonia into ammonium carbonate, and adds Epsom salt to collect the additional phosphate left over. This method extracts most of the nitrogen and phosphate, and leaves behind undesirable drugs and chemicals.
With a working system, Leverenz and his colleagues now hope to collect enough urine-derived fertilizers to permit a comparison against common fertilizers used in agriculture.