No. 1 waste is golden opportunity
- Published: March 30, 2017
On average, humans use the bathroom five times per day and produce around 125 gallons of urine per year. Ordinarily, this urine is flushed away and forgotten, a routine task that nobody wants to think about any more than necessary. But according to the Rich Earth Institute, a research institute in Vermont, that urine could be repurposed as a crop fertilizer. Peeing is a fact of life, meaning there is more than enough to go around. The question thus becomes: what are the benefits of using urine as a fertilizer, and how can be it be collected on a large enough scale?
“There is great engineering potential” in creating a better way to deal with human waste, said Kim Nace, founder and executive director of the institute. “The modern toilet is outdated.”
Scientists from the Institute recently spent a week at Antioch College exploring fertilizing with human urine. Nace, who wrote her master’s thesis on composting toilets, gave classroom presentations while Ben Goldberg worked with students to build a urine-diverting outdoor toilet. Nace also hosted a talk open to the public that outlined why the group was undertaking its unusual mission.
The week-long visit was organized by Beth Bridgeman, instructor of cooperative education at Antioch, and was sponsored by the Yellow Springs Community Foundation and co-hosted by the University of Dayton’s Ethos Institute. Nace also spoke at Wittenberg, Central State and the University of Dayton.
Modern sanitation is inefficient and irresponsibly wasteful, Nace said, as enormous amounts of energy and resources are used to dispose of disproportionately small amounts of waste: 1.6 liters of human waste creates over 200 liters of wastewater, which is sent to a wastewater treatment facility for purification. Not only are mass amounts of potential fertilizer sacrificed when the toilet is flushed, but the process of treating wastewater generally accounts for a municipality’s highest energy cost, she said. If urine were diverted, toilets would be flushed less often and thus the amount of water needed to do so would decrease proportionally.
Urine makes a great crop fertilizer because it’s rich in nutrients vital for plant growth, Nace said, such as phosphorus and nitrogen. However, releasing significant amounts of nutrient-rich water into rivers and estuaries (which is the end result of many wastewater treatment operations) promotes algae growth, which can kill mass amounts of fish and other wildlife.
The Rich Earth Institute is currently exploring alternative toilet techniques in a community in Vermont, where over 100 residents have been participating in an “informal urine collection” process. Specially-designed toilet seats feature a compartment in the front that diverts urine into a tank below, which is then taken to a pump station and transferred to a larger receptacle. Once the larger receptacle has been filled, the collected urine — around 5,000 gallons so far — is heated to 80 degrees centigrade for 1.2 minutes in a mobile urine pasteurizer and applied to crops.
“It is probably the first community-scale urine recycling project in the USA,” Nace said.
So far, urine as a fertilizer has yielded demonstrably positive results. The Institute applied diluted and undiluted urine mixtures to a hay field, with sections using traditional fertilizer and no fertilizer interspersed as controls. Over 1,600 pounds of hay per acre were harvested from areas with the diluted urine solution, a yield similar to that grown with traditional fertilizers.
“We are very pleased with the perfection of urine as a good agricultural amendment,” Nace said. Urine is also much better for the environment, as the production of the nine billion pounds of synthetic fertilizer used every year accounts for 3–5 percent of annual carbon emissions, she said.
However, a common apprehension about using urine as fertilizer concerns the residual pharmaceuticals found in human waste. The institute is aware of these concerns, Nace said, and so it set out to determine how much of these compounds were passed to the soil through human urine. Vegetables were grown with urine collected from a number of public events, and a study measured the presence of 16 drugs in parts per trillion over two years.
Based on their findings, these concerns seem to be unfounded. A person would have to eat one pound of lettuce per day for the next two thousand years to ingest the amount of caffeine in an eight ounce cup of coffee, Nace said, and that same person would have to eat 154,000 carrots to equal one 500 mg tab of Tylenol. Furthermore, UV rays and microbes in the soil tend to break down compounds, she said.
The urine collected for these tests was done so in an outhouse like the one Antioch students built with Ben Goldberg during the Institute’s visit last week. Approximately 25 students cut boards, pounded nails and helped set up the tanks and hoses for liquid and solid waste. The outhouse boasted the standard divided toilet seat. Goldberg is a carpenter, and the craftsmanship of the outhouse speaks for mastery of the trade.
Bathroom users would be hard-pressed to find a nicer outhouse, he said.
Goldberg was happy to point out the features of the outhouse, such as the cedar walls, which made it relatively light, and the hand-carved wooden door latches. Wooden rails on the bottom allow the outhouse to be transported with relative ease. The finished toilet is currently located on the Antioch farm, though nobody is allowed to avail themselves of its amenities, Bridgeman said, as Ohio environmental regulations currently prohibit the use of such toilets. However, speaking with lawmakers about the issue is another part of the Institute’s mission.
“It’s easy to see that using drinking water to flush toilets is not really a good idea,” Bridgeman said. “Ohio has a chance to get in on [the ground floor]. Hopefully we can be on the cutting edge after Vermont.”
Overall, the idea of urine fertilizer appears to be catching on, Nace said. The Rich Earth Institute was founded five years ago with a thousand-dollar grant, and the grants it has received have only grown since then, including a recent $3 million from the National Science Foundation. The institute has hosted a urine diversion summit for the past few summers in Vermont; 15 people went to the first conference, but 75 people from around the world will attend this year’s gathering, including a dramatist who wrote a musical called “An Inconvenient Poop.”
Ultimately, the institute hopes to see urine-diversion happening on an industrial scale. Nace said she has visions of urine being collected by office buildings, hospitals and stadiums, anywhere with significant numbers of people using the restroom. Underground urine tanks would become just another part of standard engineering practices, she said, though she conceded this is likely a ways off.
To paraphrase an institute pamphlet, the goal is to transform waste all humans produce into a resource all humans need. Whatever it’s called — whiz, pee, piss, tinkle or uresis — human excreta is gaining traction as a valuable fertilizer, a resource increasingly known as “liquid gold.” It’s a strange line of work, perhaps, but the benefits of urine have been driving Nace she began using jugs and testing samples in her garage.
“I’ve been thinking about this every night and every day for the past six or seven years,” she said.