Sustainable fertilizer from reclaimed urine: A farm-scale demonstration for hay production

Sustainable fertilizer from reclaimed urine: A farm-scale demonstration for hay production

Summary

The Rich Earth Institute (REI) is pioneering the use of sanitized human urine as an innovative and sustainable fertilizer. Wide-scale reuse of urine as fertilizer would provide a stably-priced, locally produced, and sustainable source of fertilizer for farms, while directly alleviating the growing problem of nutrient pollution of surface waters by septic systems and wastewater treatment facilities.

At the conclusion of REI’s second season of research, we have produced immediately applicable experimental results, increased farmer demand for urine-based fertilizers, and achieved substantial organizational growth. The SARE-funded research yielded practical insight into optimum application methods for human urine as fertilizer and have clarified questions and experimental parameters for future research. Advances were made in the infrastructure for collecting and processing urine, notably through the automation of urine pasteurizing equipment and the creation of urine collecting portable toilets for use at public events. At 3,000 gallons, urine donation increased by a factor of 5 over 2012, with 170 donors participating. Numerous presentations were given at the farm and a variety of public venues, and journalists and documentary film crews have recorded the year’s activities.

Objectives/Performance Targets

The primary objective of this project was to investigate the effect of the dilution ratio of urine with water on hay yield. Experimental field plots received sufficient urine to supply 50 pounds of nitrogen/acre, mixed with varying amounts of dilution water. In addition there was a control plot, a synthetic fertilizer plot, and two plots receiving urine at rates 50% and 100% higher than the standard rate. The purpose of the experiment was to find the minimum dilution rate necessary to maximize crop yield and minimize labor associated with application.The finding of this season’s research is that undiluted urine can be applied as fertilizer on established hayfields without causing damage to the crop. This is in contrast with recommendations commonly found in urine fertilization guides written for gardeners: namely that urine should be diluted with water before application, using urine:H₂O ratios ranging from 1:3 to 1:10, to prevent damage to plant tissues by concentrated ammonia.

Histogram of hay yield on test plots treated with (left to right) urine at selected dilutions (urine:H₂O) at 50 lbs per acre, urine applied at 150% and 200% application rates, a chemical fertilizer test plot, and an unfertilized control plot.

This finding has very significant implications for the practicality of farm-scale use of urine as fertilizer. This is because pre-application dilution at even a 1:3 urine:H₂O ratio necessitates a three-fold increase in the material volumes handled, compared with field applications of undiluted urine, resulting in significant and potentially prohibitive labor requirements.

While dilution was not necessary to prevent damage to the crop, the dilution rate of 1:1 (urine:H₂O) produced a somewhat higher yield in the strip tests, exceeding both the undiluted urine and synthetic fertilizer treatments. We hypothesize this is due to reduced ammonia volatilization from land fertilized with 1:1 diluted urine, but further experimentation is necessary to confirm this.

The more conservative and labor-intensive 1:3 (urine:H₂O) ratio produced no yield benefit in either trial and required the most effort, leading us to recommend against dilution at this high rate.

Application of undiluted urine at rates in excess of the standard rate showed yield increasing linearly with application rate, further indicating that there was no negative effect caused by the undiluted urine.

This year’s work helped to establish an appropriate scale for plot size in our field trials on established hayfields. The 4m x 4m replicated treatment plots with random distribution showed highly variable yield results in the harvests both before and after fertilization, complicating statistical analysis. (Analysis to be presented in final report.) Compared with the 4m x 4m plots, the more extensive 5.5m x 100m strips showed less variability between treatments and a greater difference between treatments and control. We suspect that this is because larger plots have a buffering effect on variability in soil quality, relative species abundance, and stand establishment.

Advances were made in the collection and transport of urine, with 3000 gallons of urine collected from 170 donors. In partnership with Best Septic of Westminster, Vt., specially modified urine-collecting portable toilets were created and piloted at the Strolling of the Heifers Festival in Brattleboro Vt. and then utilized again at three additional public events. Based on the response this year, we expect to have even more urine donors next year. Best Septic has plans to supply more public events with specially branded urine collecting portable toilets, which have proven to be an excellent outreach tool.

The solar pasteurization system built in 2012 was upgraded during the spring of 2013 to constantly monitor and record the temperatures within the pasteurization vessel, and to automatically empty and refill the vessel once pasteurization criteria were met. This second iteration of the equipment created a more robust system that was easier to operate and to monitor. Our farmer partners were able to safely and successfully operate the equipment independently with limited REI support.

The Brattleboro Municipal Wastewater Treatment Facility is supporting REI’s work by storing 1,000 gallons of urine at the facility over the winter months in preparation for a spring application to hayfields in 2014.

• Hay yield experimental results

Impacts and Contributions/Outcomes

As a result of this year’s research and outreach, two additional farmers have signed up to receive urine fertilizer next year and participate in field trials, and a third is on a waiting list and will receive urine if enough is collected.

As noted, preliminary analysis of the experiment indicates that dilution is not necessary to avoid damaging established hay. 1:1 dilution may be beneficial, but higher dilution rates are unnecessarily labor intensive. This is important because it establishes a labor-efficient method for urine application.

Presentations were made at the following conferences and events:

-Slow Living Summit, Brattleboro, VT
-World Toilet Day, United Nations
-New England Water Environment Association (NEWEA), Boston MA
-NOFA Summer Conference, Amherst MA
-VT Biosolids Forum

A booth and/or urine collecting portable toilet were at the following events:

-Strolling of the Heifers, Brattleboro, VT

-2013 Vermont Organics Recycling Summit, Randolph, VT
-Vermont Solar Fest, Tinmouth, VT
-International Bio-Char conference, Amherst MA.

Some planned future educational outreach includes:
Presentation at VT Grazing and Livestock conference, January 2014

Vermont Public Television is producing a segment on REI for release in March 2014.

• Jay and team applying urine 2013
• Konrad applying urine with handheld boom 2013
• Seth pumping urine with septic truck 2013
• Hay drying on randomized plots 2013

Collaborators: