Value-added products from urine: Enriched compost and stabilized liquid fertilizer
The Rich Earth Institute 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.
In the fourth season of field trials using urine as fertilizer, the Rich Earth Institute collected over 5,000 gallons of urine for use as fertilizer on hay. In continuation of our previous field trials on yield effects from urine and synthetic fertilizer, undiluted urine and synthetic fertilizer were applied side-by-side in a controlled field trial, with a reduced number of treatments and an increased number of replicates in order to gain more statistical power. Full statistical analysis will be included in the final report.The Rich Earth Institute developed a new, high-capacity, portable pasteurization system for recycling urine into fertilizer, and received a long-term state permit allowing it to produce and distribute urine-derived fertilizer for farmers to use without restriction.
In a related but separate project, the Institute continued EPA-funded field trials to assess the persistence of residual pharmaceuticals from urine-based fertilizers in vegetable crops, soil, and groundwater.
We received a 10-year permit for a portable urine sanitization facility from the Vermont Department of Environmental Conservation on May 15, 2015. This allows us to process up to 500,000 gallons of urine per year, at participating farms or other facilities throughout the state. Construction of the new continuous-flow urine pasteurizer was completed in May, and it was used for all urine treatment in 2015.
Performance tests of the pasteurizer show it to be capable of processing 720 gallons of urine per day with a heat recovery rate of approximately 80%. Assuming an electricity cost of $0.15/kWh, the cost to pasteurize urine using this device is approximately 0.9 cents/gallon, or $9.00/1000 gallons.
Given time and funding, we will develop a third-generation pasteurizer for the 2016 season, with the goals of boosting efficiency, durability, and processing speed, while decreasing size and mechanical complexity. This will allow for more efficient urine processing and may result in a design that can be used in other urine recycling projects.
We completed a fourth season of field trials, comparing the efficacy of urine-derived fertilizer in comparison with synthetic fertilizer for growing second-cut hay. Building on the 2014 trial, we revised the treatments to gain more statistical power for determining best practices for the application of urine-derived fertilizer. We also performed an initial field test of a new, concentrated urine-derived fertilizer product.
The location for the field trial was changed from Fair Winds Farm to Whetstone Valley Farm, due to a successful field season at Whetstone Valley Farm in 2014 and the preference of the farmers at Fair Winds Farm to avoid further application of synthetic fertilizers.
The Whetstone Valley Farm study plot layout from 2014 was retained for 2015, utilizing a 100 m x 66 m test plot divided into 12 subplots, each measuring 5.5 m x 100 m. The three subplots used as no-fertilizer controls in 2014 were reused as no-fertilizer controls in 2015. Eight of the remaining nine strips were redistributed into two treatments with four replicates each: pure urine or synthetic fertilizer. This was done in order to increase the number of replicates for these treatments from three in 2014 to four in 2015. The remaining subplot was treated with a concentrated urine product in order to test its effect in a controlled but not-statistically-significant manner.
Synthetic fertilizer (urea, triple superphosphate, and KCl) was applied to four subplots at Whetstone Valley Farm on 8/9/15 prior to an overnight 1.4” rain event, with NPK application rates matched to the levels to be applied in the urine treatment. Soil moisture at the time of the synthetic fertilizer application in the top six inches of soil (as determined by air drying core samples at room temperature) was 24%.
A total of 458 gallons of undiluted urine were applied to four subplots the following day (8/10/15), during which time the weather remained overcast following the overnight rain event. The Agricultural and Environmental Testing Lab at UVM reported nutrient concentrations in the urine of 7.100 g/L total N, 0.399 g/L total P, and 1.427 g/L total K. Soil moisture in the top six inches (as determined by air drying at room temperature) was 30%. Dominant species were perennial grasses timothy, orchardgrass, and reed canarygrass, with scattered red clover, growing in Marlow fine sandy loam.
42 gallons of concentrated urine (produced using reverse osmosis) were spread on the remaining subplot. The UVM lab reported total P concentration of 2.060g/L and total K of 6.866g/L. Based on the 5x concentration from the original feedstock, total nitrogen was estimated to be 28g/L.
No scorching or browning was evident in any of the subplots, and growth on all the treated subplots was visibly taller and more lush. The hay was cut by the participating farmer on 11/2/15 with Rich Earth Institute staff present, and then baled on 11/4/15 with assistance by Institute staff who tagged bales with subplot identifiers.
Bales were weighed on 11/7/15, and core samples were taken to determine moisture content. Core samples were air dried indoors until 12/17/15 and then reweighed. Total yield values reported in Figure 1 represent the total measured weight of the bales adjusted to their air-dried equivalent.
The composting and stabilized leachate portions of the 2015 SARE study remain to be completed, and are scheduled to to be conducted in the early spring. We will continue the bench-scale trials still underway as part of our 2014 SARE project, and use the results to determine final parameters for the setup and operation of the large bin trials to be conducted for the SARE 2015 study.
March–May: Urine collection, transport, storage
- Urine donor community kick-off event April 10, 2015 held at the River Garden in Brattleboro featuring Get on the Bus Productions presenting “What do we do with our Poo.”
- Bought, configured, and tested a reverse osmosis machine for removing the water from urine to create a concentrated fertilizer product.
- Acquired ten year permit from VT Watershed Management on May 15th, for mobile urine pasteurizing unit.
- Completed spring pump-out route with Best Septic from 10 homes that are using 55 gallon barrels for collection.
- Filled existing farm tanks with urine.
- New mobile pasteurizing unit built and tested.
June–July: Urine treatment
- Additional urine collected, transported to farms, and treated.
- Improvements made to pasteurizer, based on operational experience.
August–October: Urine application
- Urine and chemical fertilizer applied at Whetstone Valley Farm on 8/10, after first cut of hay.
- Additional pasteurized urine applied to other hay fields at Whetstone Valley Farm 8/25 and 8/26.
November–December: Hay harvested, Fall Urine Application
- Completed fall home collection pump-out route 11/6/15 from 10 homes that are using 55 gallon barrels for collection.
- Cut (11/2/15), dried, baled (11/4/15), and weighed (11/7/15) at Whetstone Valley Farm.
- Total urine collected in 2015 over 5,000 gallons.
- Urine collection continues through the winter.
Still to be completed:
- Full statistical analysis of field trial results
- Bench-top compost trials
- Bin-scale compost trials
Impacts and Contributions/Outcomes
The field trial showed that when pure urine and synthetic fertilizer were applied at the same NPK loading rates, yields were not significantly different. In the 2015 trial, which used more replicates than the 2014 trial, yield of the synthetically-fertilized strips averaged 10% higher than the urine-fertilized strips, but the difference was not statistically significant. Average yields from the urine-fertilized and synthetically-fertilized strips were 84% and 103% higher than the control, respectively.
This finding is important because it confirms results from the 2014 trial that undiluted urine can be applied effectively to hayfields under moist soil conditions using simple and inexpensive equipment, without the labor-intensive step of diluting the urine prior to application. Given that the synthetic fertilizer was applied at the ideal moment, (on an overcast day hours before the beginning of a 1.4” rain event,) it can be assumed that the field conditions represent a best-case scenario for synthetic urea incorporation and subsequent utilization. Because the yield from urine-fertilized subplots was within 10% of that of the synthetically-fertilized subplots, we assume that ammonia losses from the applied urine were low.
Therefore, applying undiluted urine to moist soil after a rain event appears to be an effective and efficient means of fertilizing hay.
It should be noted that 2014 results showed a 16% yield increase when urine was diluted 50:50 with water before application instead of being applied undiluted–but while highly suggestive the difference was not statistically significant. Further study with a substantially larger number of replicates would be needed to determine whether this effect was real. Furthermore, in our judgement the labor and equipment time that would be required to transport water for dilution would likely negate the practical benefit, even if the effect proved to be real. Therefore the 2015 field trial focused on application to moist soil, where water in the receiving soil could result in in-place dilution of the urine by soil water.
In addition to the SARE-funded research, the Rich Earth Institute completed a second and final season of field trials funded by the EPA as part of a study to determine if any pretreatment of urine to remove residual pharmaceuticals is advisable before urine is used as a fertilizer. The study, which assesses the persistence of pharmaceutical residuals from urine in soil, crops, and groundwater, is being conducted in collaboration with partners at the University of Michigan, University at Buffalo, and Hampton Roads Sanitation District. The Institute grew lettuce and carrot crops in situ, amended with urine, struvite, and synthetic fertilizers. Samples of urine, soil, groundwater, and crop tissues are currently undergoing chemical and biological analysis at labs at the participating universities. Final research results will be available in 2016.
The Rich Earth Institute’s work continued to generate local, regional, and national media attention including:
- 10 minute video: Peecycling, University of Michigan, April 1, 2015
- Local articles in the Brattleboro Reformer and The Commons
- National articles in USA Today (from Burlington Free Press), The Guardian, and The Boston Globe
- Institute staff travelled to Montpelier, Vermont twice in the spring to testify to meetings of the Fish, Wildlife and Water Resources Committee, the Agriculture and Forest Products Committee, and the Windham County legislative delegation.
- Kenya – Managing Director Kim Nace travelled to Nairobi where she presented Rich Earth Institute’s progress and findings to NGO project staff at Sanergy and other NGO projects, USAID, and World Bank sanitation leaders.
- Invited and sponsored by colleagues from Recode in Oregon, Research Director Abe Noe-Hays attended both the International Dry Toilet Conference in Finland and World Water Week conference in Sweden in August and September. His three week itinerary in three countries included meetings and interviews with key stakeholders in the emerging field of urine diversion and ecological sanitation, and site visits to pilot projects.
- NOFA/Mass conference presentation, 1/10/2015
- Northeast Sustainable Energy Alliance (NESEA) annual conference in Boston in March. Directors of the Institute presented in a 2-session panel workshop titled “Rethinking the Urban Water Grid.”
- University of Michigan, 4/1/2015, Rich Earth Institute Directors presented their work to a graduate student seminar, and assisted colleagues from the EPA-funded pharmaceutical study in initiating urine collection on campus.
- WEFTEC (Water Environment Federation’s Annual Technical Exhibition and Conference) in September in Chicago. Abe Noe-Hays, Research Director, presented at this conference.
- University of Vermont – 10/30/2015 Directors presented to students at the School of Agriculture Friday seminar series.
In November, 2015, the Institute launched a new website.
15 Christine Court
Vernon, VT 05354
Office Phone: 9784791450
511 Upper Dummerston Road
Brattleboro, VT 05301
Office Phone: 8022549067
Whetstone Valley farm
114 Cooke Road
Brattleboro, VT 05301
Office Phone: 8022570175