Urine as fertilizer: Maximizing hay yield and enriching low-N composts

Final Report for ONE14-218

Project Type: Partnership
Funds awarded in 2014: $14,955.00
Projected End Date: 12/31/2015
Region: Northeast
State: Vermont
Project Leader:
Abraham Noe-Hays
Rich Earth Institute
Kim Nace
Rich Earth Institute
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Project Information


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 can 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 third season of field trials using urine as fertilizer, the Rich Earth Institute collected approximately 4,500 gallons of urine for use as fertilizer on hay. In order to refine the previous year’s study on yield and the effect of diluting urine at the time of application, 1,717 gallons were sanitized and applied to expanded test plots on two farms. Treatments included pure sanitized urine, urine diluted 50/50 with water, and synthetic fertilizer (all applied at a rate of 50 lbs. nitrogen/acre) and a no-fertilizer control. Results confirmed previous findings that diluted and undiluted urine are both effective fertilizers, increasing yield in second cut hay. Data also showed that urine diluted 50/50 with water produced moderately (16%) higher yields than undiluted urine, though the difference did not reach significance and further tests would be needed to show if this difference is real.

The bench-scale composting trial tested four feedstock combinations including horse manure, wood shavings, and shredded leaves. Shredded leaves proved most effective at retaining the nitrogen (N) from urine in the finished compost product, retaining 83% of the total N present at the beginning of the composting process. The recipes combining wood shavings, horse manure, and urine retained between 45% and 53% of the total N.

In a related but separate project, the Institute began EPA-funded field trials to determine the persistence of residual pharmaceuticals from urine-based fertilizers in vegetable crops, soil, and groundwater. This two-year project, (performed in partnership with the University of Michigan, University at Buffalo, Brown and Caldwell engineering firm, and Hampton Roads Sanitation District in Virginia,) will help determine whether there is any need to reduce pharmaceuticals in urine before it is used as fertilizer.

The Institute also asked recipients of the Vermont Grass Farmers Association’s Pasture Calendar publication to take a formal farmer survey to gauge farmer interest and capacity for use of urine as fertilizer, and received 51 farmer responses. 54%, said that they had heard of urine recycling prior to the survey, and 54% would be interested in a using a urine-based compost product. Concerns were primarily about the safety of using urine as a fertilizer and particularly about the pharmaceuticals which could be in the urine.



Our project addresses two seemingly separate problems, one affecting farms and the other affecting the natural environment. Both problems center on the availability of nitrogen and phosphorus, and each problem, if addressed correctly, can provide the solution to the other.

Problem 1 – Unsustainability of synthetic fertilizer – Fertilizer prices have risen sharply in the last ten years and are a major expense to farmers. Nitrogen prices are tied to the volatile price of fossil fuels, which are projected to rise in the long term despite the current gas boom. Phosphate is a finite resource, subject to politically induced price swings, and the Global Phosphorous Research Initiative is predicting a shortage of high-quality rock phosphate within 40 years. All told, reliance on synthetic fertilizers is an unsustainable and uncertain option.

Problem 2 – Nutrient pollution – Ponds, lakes, and coastal estuaries throughout the Northeast are heavily impacted by nitrate and phosphate pollution caused by human activity. While agriculture is implicated to some degree, wastewater from homes and businesses is often the principal source of nutrient pollution in more populated watersheds, primarily due to the urine it contains. 70% of the nitrogen and 50% of the phosphorous in wastewater is from urine, with feces contributing a relatively small share. Many wastewater plants and most septic systems are unable to control this nutrient pollution and are poorly suited to nutrient reclamation.

The only common method for reusing nutrients from human waste is land application of sewage biosolids, which can contain heavy metals, chemical wastes, and other persistent pollutants. Biosolids also contain only a small fraction of the nutrients that present in sewage, with the rest commonly being discharged into rivers as effluent.

However, diverting urine from the wastewater stream for recycling into fertilizer, removes the majority of nitrogen from wastewater and carries no risk from heavy metals or industrial chemicals. Diverting urine from the waste stream (using specially equipped toilets and urinals) protects water quality by recycling N, P, K, and micronutrients back to agriculture. This produces a sustainable, local fertilizer that has the potential to be a dependable and inexpensive resource for many farmers.

As fertilizer prices climb and the cost of conventional sanitation rises, converting urine into fertilizer will be an increasingly profitable solution for both those with fertilizer needs—farmers—and those with wastewater disposal problems—homeowners and municipalities. To reap the benefits of this novel strategy, American farmers need well-documented guidance based on practical experience in successful demonstration projects.

Two challenges of using urine as fertilizer are that: 1) it is rather dilute, containing only 6 grams of nitrogen per liter; and 2) the nitrogen is present as ammonia, which can be lost to volatilization if not handled carefully. This research provides data on two strategies for addressing these issues.

One strategy to avoid ammonia loss is to mix the urine with additional water at the time of application so it will soak more deeply into the soil. But this makes the urine even more dilute, requiring additional labor to handle and spread. This study selected the most successful treatments from the 2013 field season and applied them to additional replicates to investigate the effect of dilution when using urine to fertilize hay, in order to avoid ammonia volatilization and achieve maximum yield.

Another strategy is to use urine in making compost, converting the ammonia to less volatile ammonium nitrate or organic nitrogen while also driving off a portion of the water through evaporation. No expensive tanks are needed for urine storage, and the product is a stable, more concentrated fertilizer, compatible with manure spreaders. This also helps balance the high phosphorus levels often found in compost, because urine is proportionately high in nitrogen. Laboratory composting testing of four different compost recipes quantified their relative effectiveness at retaining the N from added urine.

Researching dilution rates helps establish best practices for liquid urine application. Researching co-composting strategies provides initial data on an alternate methodology for urine-based fertilizer application using a familiar product—compost. Depending on the scale and practices of a given farm, one or the other method may be easier to adopt. By exploring new methodologies while refining established ones, we increase the rate at which sustainable urine-based fertilizer can be brought to scale.

Participating farmers who were directly involved in conducting the field research included Jay Bailey from Fair Winds Farm, Jesse Kayan from Wild Carrot Farm, and Dean Hamilton from Whetstone Valley Farm, all located in Brattleboro, VT.

Project Objectives:

Goals for 2014 included:

  • an increase in the volume of urine collected and recycled as fertilizer
  • increased labor- and energy-efficiency in the processing and application process
  • quantification of the effectiveness of urine as fertilizer on hay crops using two different application methods
  • evaluation of several compost recipes for incorporating the volatile nitrogen present in urine into a stable compost product
  • outreach to farmers and other researchers

Urine collection commenced in March, following a public “Urine Donor Kick-Off” event held in Brattleboro and attended by a standing-room-only audience of over 200 people, including urine donors from the previous year and interested farmers. Institute staff presented a summary of the previous year's work, an explanation of the project's rationale, and an outline of upcoming projects. Our partners at Best Septic Services of Westminster brought a specially converted urine-collecting portable toilet, which was used to collect urine throughout the event. It was customized with a decorative and informative vinyl wrap. Examples of urine diverting toilets for residential installation were also on display.

The depot where participants bring collected urine was upgraded for efficiency and ease of use in March with the addition of a new self-service electric pump station designed and built by the Institute. It allows urine donors to easily and hygienically pump out their own containers. This pump station has remained in use to the present time, requiring only minor modifications to the automatic electric switching mechanism.

Delays in the state permitting process for the redesigned pasteurizer precluded its use to prepare urine for the 2014 growing season. Therefore all urine used in the 2014 season was treated through the long-term storage method (>30 days at or above 20°C). The permit has since been issued and the new pasteurizer was built in 2015, with a tested processing capacity of approximately 750 gallons/day. Further performance data will be detailed in the final report for our SARE-2015 experiment.

Field trials were executed as proposed, with the modification of adding replicates to enlarge the study area on one farm, while eliminating another farm from the study due to logistical issues, as detailed in the methods section.

The first run of the composting trial went as planned, but the second run experienced technical difficulties with the aeration system, with the result that a third run will need to be performed, and reported in the SARE-2015 final report.


Click linked name(s) to expand/collapse or show everyone's info
  • Jay Bailey
  • Dean Hamilton
  • Andrew Rice


Materials and methods:

Hay yield field trial:

Our primary field trials occupied 12 randomized strips at Whetstone Valley Farm, and 9 at Fair Winds Farm, all measuring 5.5 m x 100 m (18’ x 328’). Treatments included pure urine, 1:1 urine/water mix, synthetic fertilizer, and unfertilized control. Each treatment includes three strips, enabling statistical analysis. The synthetic fertilizer strip was omitted at Fair Winds Farm because of a policy against using synthetic fertilizers on that farm.

Nitrogen (N), phosphorus (P), and potassium (K) levels in the urine used in this experiment were quantified by the Agricultural and Environmental Testing Laboratory at UVM. After the first cutting of hay, all urine-treatment strips received enough urine to apply nitrogen at 50 pounds/acre, delivered at ground height through trailing hoses using the institute’s custom applicator. The 1:1 urine/water treatment received the same amount of water as the undiluted urine strip, with the addition of an equal volume of water. The quantities of P and K delivered to these strips was also calculated, and the synthetically fertilized strips received the same NPK rates as the urine strips, through application of urea, triple superphosphate, and KCl applied using a hand-push pelletized fertilizer spreader.

Hay was cut and baled using standard haying equipment, with all bales from each strip being labeled and subsequently weighed, and representative bales cored for dry matter determination.

Composting benchtop trial:

Our objective for this experiment was to concentrate nutrients from urine by driving off excess water through composting, and to produce a compost that has a higher nitrogen:phosphorus ratio than typical animal manure compost.

We tested four compost recipes incubated at a temperature of 30°C. Substrate recipes were as follows: 1, 2, 3) horse manure mixed with dry wood shavings at 85%, 70%, and 40% manure by wet weight, and 4) dry shredded leaves. We placed each substrate mixture in a 20 liter aeration vessel, wet it to capacity with treated urine, and incubated it at 30°C. (A 30°C environment encourages mesophilic nitrifying bacteria, while 50°C is a more conventional composting temperature.) Bedded horse manure and dry hardwood leaves were specified because of their high C:N ratios, which would be improved with urine.

An adjustable air supply ensured adequate aeration. Automated monitoring of the oxygen levels in exhaust air provided feedback to the aeration system, which was programmed to adjust the aeration rate of each vessel individually to maintain at least 10% oxygen in the exhaust.

Ammonia volatilization was quantified by bubbling all exhaust air from each vessel through trap containing 1 L of 0.25 N sulfuric acid. 10 mL of acid solution was removed from each trap periodically and titrated to pH 7.0 with 0.5 M (later 0.25 M) NaOH to determine how much acid had been consumed, and by extension how much ammonia had been trapped.

Additional urine was to be added to the compost as needed to maintain a moisture level of at least 50%, but moisture levels never dropped low enough to require this. Leachate was recycled as the absorptivity of the compost allowed, but excess leachate was removed and stored for analysis. Composing was begun on 1/26/15 and samples were removed for analysis on 3/16/15.

An additional trial was begun on 1/19/15, with the intention of maintaining an incubation temperature of 50°C for the active composting phase, but a leak in the aeration pump limited air flow to the vessels while simultaneously introducing fresh air to the exhaust stream, resulting in inaccurate oxygen readings. By the time the problem was correctly diagnosed, the compost had been exposed to low-oxygen conditions for an extended period, which was deemed to be too large a deviation from the experimental design for the trial to continue as planned. An additional 50°C trial is planned, the results of which will be described in the final report for our SARE-2015 project.

Research results and discussion:

Hay field trials:       

Approximately 1000 gallons of urine were taken to Fair Winds Farm and 1500 gallons to Whetstone Valley Farm and enclosed in purpose-built, unheated greenhouses made of clear plastic film stretched over wooden frames. As in 2013, electronic temperature sensors were submerged in the tanks and connected to a datalogger which recorded time-stamped temperature readings for periodic retrieval, the results of which are shown in Figure 1. Both greenhouses performed adequately, producing a sanitized product for use by mid-July, which was compatible with the fertilizing needs of second cut hay on these farms. For fertilizer application earlier in the season, pasteurization would be a better method.

Figure 1. Figure 1.

The original proposal called for only two replicates of each treatment at Fair Winds Farm, but we increased the number to three in order to increase statistical significance. 811 gallons of urine fertilizer were applied on 7/29/2014. Treatments included undiluted urine, a 50/50 urine/water mix, or no fertilizer. UVM extension testing reported nutrient concentrations in the urine of 6.304 g/L total N, 0.374 g/L total P, and 1.370 g/L total K. Soil moisture in the top six inches (as determined by air drying at room temperature) averaged 17%, with a standard deviation of 0.54%. Dominant species were perennial grasses timothy, brome, orchardgrass, quackgrass, and reed canarygrass, with scattered red clover and vetch growing in Quonset and Warwick soils.

906 gallons were applied at Whetstone Valley Farm on 8/15/14. Each treatment was done in three replicates, including the same treatments as at Fair Winds Farm with the addition of a synthetic fertilizer treatment (urea, triple superphosphate, and KCl) with total NPK levels matched to the quantities applied to the urine-treated strips. UVM extension testing reported nutrient concentrations in the urine of 5.381 g/L total N, 0.329 g/L total P, and 1.300 g/L total K. Soil moisture in the top six inches (as determined by air drying at room temperature) averaged 31%, with a standard deviation of 1.8%. Dominant species were perennial grasses timothy, orchardgrass, and reed canarygrass, with scattered red clover, growing in Marlow fine sandy loam.

Urine fertilizer application at Hogget Hill Farm was omitted because the farmer needed to fertilize before we had enough sanitized urine available. Hogget Hill was the least important site because the other two trials included replicates and multiple treatments, while Hogget Hill was to be a simpler demonstration with no replicates.

Compared to 2013, the urine fertilizer application process was much faster due to a faster transfer pump. A 180 GMP gas-powered Honda pump transferred urine and dilution water from the storage tanks to the applicator roughly 25 times faster than the 7 GPM pump used in 2013. At this rate, the shortest pumping time required per 1000 gallons, (enough to fertilize an acre of hay,) is six minutes.

With pumping time reduced, the time bottleneck became the speed of the applicator. The gravity-fed applicator boom and hoses delivered liquid to the ground at about 25 gallons/minute, requiring about 40 minutes to apply 1000 gallons. Using a powered pump would increase the application speed. Increasing the tank size (currently 200 gallons) would save time by reducing the number of trips required.

Hay was baled at Fair Winds Farm on 10/12/14 and from Whetstone Valley Farm on 11/11/14. Average yields (dry matter) with standard deviations are shown in Figures 2 and 3.

Figure 2 Whetstone Valley Farm yield dry mass

Figure 2.


Figure 3 Fair Winds Farm yield dry mass

Figure 3.

A complete statistical analysis of yield is included in the attached appendix. (Statistical analysis for Rich Earth Institute SARE-2014 project) To summarize, all fertilized types had a highly significant effect on yield relative to unfertilized control. The differences within the varying fertilizer types failed to reach statistical significance, though the yield difference between synthetic and undiluted approached significance. All other fertilizer pairings, including diluted and undiluted urine, showed no significant between group differences in yield.

These findings provide preliminary evidence of the rough equivalence in efficacy between diluted and undiluted urine and synthetic fertilizer in promoting hay yield.


There was a wide variation in the fraction of nitrogen retained by the recipes throughout the composting process (see Table 1). The three manure/shavings recipes all have similar N retention rates of 45-53%, while the leaf recipe has a N retention of 83%. This is keeping with the observation that all three manure/shavings recipes exhibited an ammonia odor during the compost process, while the leaf compost did not.

Table 1. Retention of nitrogen during composting by four different compost recipes Table 1. Retention of nitrogen during composting by four different compost recipes. The labels of the first three recipes reflect the fractions of manure and wood shavings.

Despite the difference in observable ammonia odor, and the data showing high N loss in the manure/shavings composts, the sulfuric acid traps for quantifying ammonia evolution all indicated low evolution rates of 0.4-0.6 g total ammonia nitrogen captured from each vessel over the duration of the compost run. It is possible that the traps were not effective at capturing ammonia, despite their apparent effectiveness during short-term testing before the compost trial began. Follow-up testing of this trapping and quantification method is needed to determine if it is accurate over the long time periods and low ammonia vapor levels involved.

Other measures are reported in Table 2. Of interest are the C:N ratios, which are quite high in the manure/shavings recipes, suggesting that much of the C in the shavings was unavailable, in contrast with the highly available ammonia-N. This mismatch in availability may account for the observed N loss.

Table 2. Analysis of compost and feedstocks Table 2. Analysis of compost and feedstocks

The leaf compost also differs from the manure/shavings formulas in the N and P fractions. The total N in the leaf compost is nearly three times as high as in the manure/shavings compost, and the P level is lower than two out of three of the manure/shavings composts. This high N:P ratio means that the leaf compost has a greater N fertilizing potential, while contributing a relatively small amount of P--which is advantageous on land that has historically received excess P from high applications of animal manure.

A 96-hour germination test using Lepidium sativum mixed 1:1 with soilless bedding media (6 replicate cells of each compost mixture, plus 6 control cells) revealed no inhibition of germination by any of the composts.



Research conclusions:

Hay trials:

The field trials showed that undiluted urine was an effective fertilizer, increasing yield in second-cut hay without damage to the grass from the free ammonia in the urine fertilizer. This is very important, because diluting the urine with water prior to application (commonly recommended in literature on urine as fertilizer) greatly increases  the labor and equipment costs of application. Using undiluted urine reduces these costs and speeds the application process.

However, there was a difference in yield between the diluted and undiluted urine treatments. Strips fertilized with a 50/50 urine/water solution yielded 16% more hay than strips fertilized with pure urine at Whetstone Valley Farm. However, this difference did not rise to the level of statistical significance, and larger trials would be needed to determine if the observed effect was real. If further study proves that dilution is beneficial, it could be achieved efficiently through mixing urine with lower-strength liquid dairy manure prior to application.


Although the second compost run remains to be completed, it is clear from the initial results that co-composting of urine with leaves can produce a compost that retains the majority of the nitrogen and other nutrients found in urine, and has the benefit of producing a solid product that is aesthetically appealing, can be stored inexpensively, and can be applied using conventional equipment.

Farmer Surveys:

Rich Earth Institute conducted a Grass Farmer Survey in October 2014 and received 51 responses. This survey went to the Vermont Pasture Network (VPN) email list maintained by UVM’s Center for Sustainable Agriculture. Due to the unpredictable nature of contacting people by email (messages being sent to spam folders, etc.) we are unsure of the total number of people who actually received the survey, but it was sent to several hundred farmers. Respondents were primarily hay farmers including some who have livestock. Of the 51 responding farmers, 75% were from Vermont, 8% NH, and the rest from other New England states and 1 from Illinois.

Most respondents primarily grow hay or pasture, with a few that also have home or market gardens or grow small amounts of vegetables. The amount of hay grown varied from a few acres to 300 with several in the 100 – 200 acre range. The majority of these hay farmers take two cuttings; some one, and some three. Some of the larger producers expressed strong interest, although they did not all provide contact information in order to learn more about this in the future.

A little more than half, 54%, said that they had heard of urine recycling prior to the survey. The great majority of responses were positive, although cautious. About 4 of the 51 respondents had initial negative responses.

Positive comments included: This is a “good use of wasted resources”; “good source of nutrients”. It could “reduce pollution of waterways”; “could be cost-effective”. The concerns were primarily about the safety of using urine as a fertilizer and particularly about the pharmaceuticals which could be in the urine. 50% of the farmers expressed concern about public perception. Other concerns were about the cost of implementing this in their farm practice. Others were under the impression that it is “prohibited by National Organic Program”. Some were concerned that urine would burn crops. Farmers expressed a need for technical support and more information about logistical details of using urine fertilizer.

60% of respondents use wood ash and lime on their fields. Synthetic N and P applications were only used by 21%.  For those who currently use no synthetic fertilizer and are interested in using urine on their fields, they would see it as an addition to their soil amendment practices, not a replacement. Therefore they expressed significant concern about the costs and would not be interested unless the price was right.

For those who do use chemical fertilizer, it is a significant expense ($425 – $735 dollars per ton,) so urine substitution could help them make substantial savings. Storing the urine prior to application was a concern for some – a few would need the urine delivered (and spread by delivery truck) and could not store at all. For others, storage no problem. The larger hay farmers had 1000- 2000 square feet available for storage.

When asked what the most important information that would inform a decision about using urine as a fertilizer, 75% wanted more information on nutrient composition and 80% wanted more information about the price. 58% wanted to know about the equipment that would be needed. Storage space, time commitment, and labor were identified as lesser concerns. Under “other” many added concerns about pharmaceuticals and hormones, as well as legal issues and  many added that they would want technical assistance for proper usage. 54% would be interested in a using a urine-based compost product.

A second Farmer Interest Survey, built upon the Grass Farmer Survey was created in March, 2016 and has been tested with a small pilot group. It will be disseminated in the fall of 2016.

Participation Summary
2 Farmers participating in research

Education & Outreach Activities and Participation Summary

Participation Summary:

Education/outreach description:

The Rich Earth Institute's work has generated regional, national, and international media attention including: online articles on NPR’s “The Salt”, National Geographic, Modern Farmer, BBC Mundo (Spanish), Grist, and the Guardian, television coverage by Vermont Public Television, and radio interviews on VPR, the CBC, and the Australian Broadcasting Corporation. The Burlington Free Press published a feature article about Rich Earth’s work in November 2015 which was then reprinted in USA Today. Most of these publications can be accessed through our media page at http://richearthinstitute.org/publications/rich-earth-in-the-news

In August of 2015, the Rich Earth Institute held a Urine Diversion Summit, a full day round table discussion for academic and industry leaders who are working in this emerging field to come together and meet each other. The event attracted 15 attendees from Michigan, Florida, California, Maine, Virginia, New Hampshire, Vermont and Switzerland, and was successful in creating a new network for support and collaboration. The event was so successful that it is being expanded for 2016 to two days with an invitation list of over 60 individuals. Rich Earth’s plan is to host this summit every year, in order to strengthen and expand this network of researchers and practitioners.

In October 2015, Rich Earth launched a new website: www.richearthinstitute.org

Local outreach included a urine donor kick off event 3/28/14 which included participating and interested farmers. More recently in January, 2016, a stakeholders breakfast was held at the Centre Congregational Church with approximately 50 people attending. Participating farmers Jay and Janet Bailey spoke with attendees about their experience and their suggestions for future work.

In both 2014 and 2015, Rich Earth team joined the Strolling of the Heifers parade in Brattleboro, VT, and had a booth at the Green Living Expo which was attended by thousands. Rich Earth was notable at this event because we supplied ten portable urine collecting toilets with signage indicating that the urine would be used as a fertilizer on local farms. Volunteers handed out “I donated” stickers and talked with people about Rich Earth’s work throughout the day.

Founders of the institute have been actively promoting the concept of urine diversion and reuse as a fertilizer by presenting at schools, colleges and universities and conferences. Rich Earth presented research findings at the NOFA/MASS Annual Winter Conference at Worcester State University in January 2015. Because major economic incentives for urine diversion stem from its potential to conserve water and prevent water pollution, we also present at conferences related to water and wastewater, or innovations in buildings and infrastructure (including the Water Environment Federation’s WEFTEC conference in Chicago and the Northeast Sustainable Energy Association’s Building Energy conference in Boston.)

In the past year,  Rich Earth’s work has been featured in four professional journals: Planning Magazine, Pumper Magazine, Public Works Magazine, and Water, Environment and Technology.

Project Outcomes

Project outcomes:

Farmer Adoption

Jesse Kayan, owner of Wild Carrot Farm in Brattleboro, says, “Our farm uses land that has been the recipient of Rich Earth’s urine applications for many years now. Having used their product as fertilizer on our small, diversified farm we have had the opportunity to experience the benefits of this system directly. As a result of past destructive practices, our hay land is fragile and low-yielding. Over the several years the Rich Earth Institute has applied urine, we have watched our yields increase dramatically. As a result, we can now make a whole additional cutting of hay each season, increasing our productivity and profits. The urine has not only increased our land’s value, it has helped make significant improvements  to the soil’s fertility and resilience. We feel extremely good to be building our soil while removing a pollutant from the waste stream.”

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.