On November 9, I’ll be joining hundreds of activists, gardeners, farmers, entrepreneurs and researchers from across the planet at the ninth annual Rich Earth Summit. For me, it's an absolute honor to briefly hold the virtual microphone and share my ongoing work with urine as a fertilizer; below is a snapshot of a few projects I’ll be speaking about.
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| Standing in the field: 2022 urine-fertilized corn trial |
Starting in fall of 2021, I rallied 10 of my friends and coworkers to collect their urine. By February 2022 I had amassed some 180 gallons, stored in a sealed IBC tote in a solar-heated kiln space on the far end of the Living Web Farms’ shop. Some were more zealous contributors than others - one person offered up an average 3.2 gallons a week, others had had enough after just one gallon. The goal was to collect 250 gallons with enough time to fully sterilize (via hydrolysis by urease) before application in a large-scale field trial at one of the recently acquired Living Web properties with comparably poor fertility. Sterilization via hydrolysis requires airtight storage for an extended time for urease to naturally convert urea and water into alkaline ammonia, hydroxide and carbonate ions, thus raising pH and killing off any potential pathogens that may have crept in. The WHO has published guidelines on this, recommending between 1 and 6 months of storage, the latter of which applies when fertilizing food for human consumption. We ended the collection period in February at 180 gallons. By then we decided its best use was for application on bloody butcher dent corn, grown exclusively as part of a complete pelleted poultry feed; 4 months of storage at mostly above 70 degrees F would suffice, before our first application in June.
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| Hydrolysis of Urine: Leave it alone in a sealed container and this happens naturally. |
The Trial:
The goals with urine-fertilized-corn trials were sprawling and multifaceted:
First, I wanted to explore the feasibility of a urine collection program, and specifically explore how willing people would be to collect their urine over the long run. Only 4 out of 10 people donated more than once. Out of those four, the top three donors worked on the farm and contributed weekly for at least 3 months. Interestingly, lab analysis of our communal urine indicated only .45 lbs N / gal, significantly lower when compared to published data from other more organized programs in Vermont and Europe.
Second, I wanted to prototype low-cost application equipment that was accessible to conventional farmers and worked in conjunction with a typical spray rig. For obvious reasons, urine shouldn’t be sprayed foliar; we’d have to have targeted applications at ground level, while also being able to clear the tops of the corn plants without breaking their stalks. Ultimately I settled on a design featuring a 10’ pipe, supported by a steel rack mounted on the back of a 50-gallon mobile spray tank. Individual ports with shutoff valves and 8’ long EPDM rubber hoses were tapped at 16” intervals, allowing for moderately precise application, in the rows, at ground level. In practice, our applications became much less precise as the corn plants grew taller, interfering with the trailing hoses, in some cases lifting them off the ground entirely. If I ever do this again, I’ll opt for some kind of weighted hose.
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| Fabricating the manifold for trailing hoses. |
Third, I wanted to visually demonstrate the impact of urine as fertilizer in a side-by-side comparison with a non-fertilized control group. I also wanted to get a sense of how corn responded to different application rates of urine-derived nitrogen. We chose to do four plots: two control groups, one group at a 140 lb N/acre rate, and another at the higher 200 lb N/acre rate. Following flame cultivation, all plots would receive compost prior to seeding.
Plot size was determined by N content and quantity of urine: 73 gallons on roughly 1000ft2 comprises the 140 lb N/acre rate, 105 gallons over the same space is the equivalent of a 200 lb N/acre application. Urine was applied evenly over 4 separate applications throughout the growing season, each time diluted 50% with water.
The Results:
The fertilizing effect of urine was obvious in less than a week following the first application on 4” plants. Fertilized plants were greener, and noticeably taller after two weeks. Additionally, weed pressure was pronounced, requiring hand cultivation at least three times during the first 6 weeks.
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| 6 weeks in: color makes it clear |
By the final application of urine in mid-July, the fertilizing effect between the control and low-rate treated plot was abundantly clear, and treated plants would continue to grow at an outpaced rate throughout the season. Interestingly, it was nearly impossible to visually indicate the line marking low and high rate fertilized plots. Some sections in the control plots had not grown dense enough to shade weeds that would further contribute to their lackluster average yields. Corn in rows growing adjacent to the trial area had also grown more densely, indicating urine was moving across the soil more than previously expected.
All sections were harvested in early November, dried for two weeks in the solar-heated kiln space, shelled, and weighed separately:
140 lb rate: 114 lbs
200 lb rate: 125 lbs
Application of urine at the comparatively lower rate showed a nearly 3-fold increase in yield, with just modest further gains at the higher rate, indicating a diminishing point of returns that should be further explored. Furthermore, the creeping of urine through the soil indicates applications may have been too rich, and similar results could have been achieved with much less urine.
Pee to Protein
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| Is urine-fertilized corn a step towards a more balanced poultry feed? |
It probably comes as no surprise that urine is a fertilizer, and corn responds to fertilizer. Still, it’s exciting to see this validated in such a profound way. However, what is perhaps most interesting was revealed later in a feed analysis: fertilized sections had a marked increase in protein, fiber and fat content.
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| Urine-fertilized duckweed on the left, Wild-Harvested duckweed on the right: The longer roots indicate this tiny aquatic plant is trying harder to find the nutrients it needs to grow. |
Truly sustainable agriculture is all about circular economy and the Pee-to-Protein pipeline is about as close to true circularity as it gets. The future of sustainable agriculture will absolutely have to consider human waste as an input, and fertilizing with urine is a safe and simple starting place.
