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

Project Overview

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

Annual Reports


  • Agronomic: general hay and forage crops, grass (misc. perennial), hay


  • Animal Production: feed/forage
  • Crop Production: municipal wastes, nutrient cycling, organic fertilizers, tissue analysis
  • Education and Training: demonstration, display, farmer to farmer, on-farm/ranch research, participatory research, technical assistance
  • Farm Business Management: new enterprise development, feasibility study, value added
  • Natural Resources/Environment: soil stabilization
  • Production Systems: agroecosystems, holistic management, permaculture
  • Soil Management: soil analysis, organic matter, soil quality/health
  • Sustainable Communities: community planning, infrastructure analysis, local and regional food systems, public participation, public policy, sustainability measures

    Proposal abstract:

    The Rich Earth Institute (REI) works at the intersection of the sustainable agriculture movement and the sanitation industry, where there is keen and growing interest in finding ways to close the food nutrient cycle. Done well, reclaiming the nutrients in human waste provides farmers with sustainable fertilizer while reducing nutrient pollution in our waterways. Attitudes and practices toward recycling human waste are beginning to shift as both food security and the high costs of ensuring clean water and treating sewage become more pressing concerns to planners, legislators, and citizens. There is a growing body of international research on such nutrient reclamation but the U.S. lags behind. The only method commonly used – field application of sewage sludge – has substantial limitations, and until REI there has been no U.S. based practical research into truly sustainable approaches.

    REI is concluding a second year of scientifically controlled field trials demonstrating the utility of recycling human urine into fertilizer for agricultural crops. A grassroots effort, the success of this project has caught the attention of national leaders in the water quality and wastewater treatment industries as well as agronomists and EPA researchers. Local farmers and the community at large have been overwhelmingly supportive of this effort, and our new farmer partners are eager to increase the scale of the operation. REI will expand this project, involving additional farmers while investigating new strategies for maximizing the on-farm benefits of urine fertilizer while minimizing labor requirements.

    Project objectives from proposal:

    Our project involves two experiments:
    1) determination of optimum dilution rates for urine application to hay, and
    2) testing eight regimes for co-composting urine with various substrates.

    Urine for both experiments will be pasteurized at 70°C for 30 minutes, then stored until use. We will upgrade our solar pasteurizer (automated for labor efficiency using the 2013 SARE grant) with ruggedized sensors and a low-flow/high-efficiency heat exchanger, increasing processing capacity by an estimated factor of four. 1. Dilution rate field trial: The objective of this experiment is to establish whether 50/50 dilution of urine at the time of application improves hay yields. This experiment builds on our 2013 SARE project, which demonstrated that urine and synthetic fertilizers produce similar yields when applied at equal NPK rates. This research also dispelled concerns about undiluted urine injuring the crop and showed the importance of dilution rates. Application of a 25/75 urine/water mix, (recommended for certain crops by European researchers,) and undiluted urine produced substantially equivalent hay yields. All urine treatments showed increased yield over the unfertilized control, but the increase on the 50/50 urine/water strip was approximately 40% larger than the increase on either the undiluted or 25/75 strips. Because there were no replicate strips, results are indicative but not conclusive. A concurrent randomized block trial with replicates gave ambiguous results, due to natural variability between the small blocks that obscured differences between treatments.

    With 2014 SARE funding, we will expand the successful strip trial, eliminating the labor-intensive 25/75 dilution rate and testing the remaining two rates in replicate. Two new farms are joining as research partners, allowing us to conduct trials on different soil types under different management practices. Our primary trial will occupy 12 randomized 20'x300' strips at Whetstone Farm. Treatments include pure urine, 50/50 urine/water mix, synthetic fertilizer, and unfertilized control. Each treatment includes three strips, enabling statistical analysis. As in 2013, the UVM lab will analyze urine for ammonia, nitrate, soluble K, and total P. After the first cutting of hay, urine-treatment strips will receive enough urine to apply nitrogen at 50 pounds/acre. Synthetically fertilized strips will receive the same NPK rates as the urine strips, from urea, triple superphosphate, and KCl. Weather permitting, fertilization will occur at moderate temperatures with rain forecast, following best management practices for applying urea. Before fertilization, soil samples will be taken from each strip for soil fertility testing and measurement of gravimetric soil moisture by drying. At cutting, hay on each strip will be baled and weighed. Four composite samples, containing at least 20 corings and representative of each treatment, will be sent to Cumberland Valley Analytical Services for their standard forage quality analysis.

    In our analysis, we will look for statistical differences in the dry weight yield of strips fertilized at different urine dilution rates. This will show whether dilution is necessary, or if the labor-intensive transport of water, (which our farmer partners have identified as the most challenging aspect of urine reuse,) can be eliminated. At Fairwinds Farm, treatments will include pure urine, 50/50 mix, and no-fertilizer control, with two replicates of each treatment. At the request of the farmers no synthetic fertilizer will be used. At Hogget Hill Farm, pure urine will be applied to approximately one acre of a larger field, with synthetic fertilizer on the remainder. Hay from these treatments will be weighed to determine yield per acre. While less statistically robust, these trials encompass additional field conditions and are an opportunity for additional farmers to refine the logistics of urine storage and application. We will continue our tracking of the total investment in equipment and labor for treatment and urine application, in order to calculate the cost per pound of NPK involved in preparing and using urine-based fertilizer. These results will allow interested farmers to assess the viability of urine reuse on their farms.

    2. Composting to stabilize nitrogen and reduce liquid volume: Our objective for this experiment is to concentrate nutrients from urine by driving off excess water through composting, and to produce a compost that has a higher nitrogen:phosphourus ratio than typical animal manure compost. We will test four compost recipes at two composting temperatures, for a total of eight treatments.

    Substrate recipes will be as follows:
    1, 2, 3) horse manure mixed with dry wood shavings at 40%, 70%, and 85% manure by wet weight, and
    4) dry shredded leaves.

    We will fill eight 20 liter vessels following these recipes, wet to capacity with treated urine, and incubate at 30°C or 50°C to simulate conditions within a large aerated pile. (A 30°C environment encourages mesophilic nitrifying bacteria, while 50°C is a more conventional composting temperature.) Bedded horse manure and leaves are specified because of their notoriously high C:N ratios, which would be improved with urine. An adjustable air supply will ensure adequate aeration and active moisture removal. Regular monitoring of oxygen levels in exhaust air will allow calculation of the oxygen uptake rate of each compost vessel. This will allow calculation of the heat evolved. The ventilation rate of each vessel will be adjusted accordingly to ensure that the resulting evaporation rate corresponds to a heat loss rate that could theoretically be supported by a large aerobic pile with similar properties.

    Additional urine will be added to the compost as needed to maintain a moisture level of at least 50%, and urine volumes will be recorded. All leachate will be recycled into the compost. After two months, or if oxygen uptake drops below 100 mg/kg ds-hr, vessels will be removed from the incubator and allowed to cure with passive aeration. After 30 days, samples from each vessel will be subjected to Lepidium sativim bioassay and sent to the UVM lab for a full compost analysis. Compost treatments will be assessed based on total nutrient content and on the percent of total nitrogen from the feedstocks retained in the finished compost. The best performers will be recommended for subsequent larger-scale composting tests on farms.

    March through December, 2014 March–May: Urine will be collected, and the urine pasteurizer upgraded. We will assemble and test the compost incubator and associated controls. As soon as weather permits, REI team will begin to build the automated solar pasteurizer and to enclose the tanks within a mini-greenhouse, preparing for both methods of urine treatment. Because some of these activities will be conducted outdoors, snow cover will largely determine the timeline of completion. REI staff will perform construction, with a target completion date of April 30. Testing and adjustment of the pasteurizer by REI staff will follow, with a completion target of May 15.

    In April, or as the ground becomes exposed and dry, REI staff will lay out the test strips on the two new farms.

    May–June: Urine will be pasteurized. Composting of urine/leaf/wood shaving/manure mixtures will begin. Treatment of the stored urine will begin in early May, or earlier if the equipment testing is complete. Initially, the operation of the pasteurizer in its new configuration will be by REI staff, but the collaborating farmers will assume responsibility after being trained by REI staff. The septage hauler will transport additional urine to the pasteurizer as it is collected. Composting will begin in May and continue throughout this period. After two months of composting, vessels will be removed from the incubator for curing. After curing, samples will be sent out for analysis and the bioassays will be performed.

    June–July: Urine application will be done depending on the timing of the first cutting of hay on each participating farm. Samples of the urine will be sent to UVM for nutrient analysis two weeks before the anticipated application date. The cooperating farmers will apply urine to the strips using a cart-mounted tank applicator, under the supervision of REI staff. August–October: Hay will be harvested and quantified, and samples sent for analysis. Composting begins on the second batch of urine/leaf/wood shaving/manure mixtures. Hay harvest will involve all partners in the project; REI staff will clearly flag each study strip, and the farmers will cut, dry, and bale the hay with REI oversight. Yield will be quantified and forage quality samples will be taken as described and sent out for analysis. Composting begins on the second batch and proceeds in the same way as the previous batch: active composting followed by curing, sampling, and bioassay.

    We will continue to present the results of our research at conferences and forums, and through farm tours and targeted presentations. In 2013 we made in-depth presentations to farmers and public officials at the NOFA Summer Conference, Brattleboro (Vermont) Agricultural Advisory Committee, Vermont Agency of Natural Resources biosolids forum, and Vermont statehouse. We staffed informational booths at the Vermont Organic Recycling Summit (VORS), North America Biochar Symposium, and SolarFest Sustainability Conference. In 2014, we will attend the Vermont Grazing and Livestock conference in January, the NOFA Winter Conference in February, and have submitted an abstract to be presenters at VORS in April.

    We will again be highly visible in the Strolling of the Heifers parade in Brattleboro, Vermont, where we piloted urine collecting portable toilets this year. We will expand our public urine collection efforts and associated outreach in 2014 to include as many as 10 more outdoor summer events. Our collaborator in this is Best Septic of Westminster. Local farmers and visitors from across New England and as far away as Panama and Mexico have toured the test site at Fairwinds Farm in 2013. Formal open house events (4 in total) and almost daily unscheduled visitors have visited the demonstration toilet at the office of the Rich Earth Institute, while others have been to the farm to photograph the fields, the urine tanks and the solar pasteurizer. We have hosted the Brattleboro Department of Public Works and will soon host the Windham Regional Planning Commission for a lunch and round table discussion of our project.

    On April 30th of 2013, EPA officials, engineers and town planners from several states attended our first large-scale urine transport by licensed septage hauler. We will continue to invite farmers and other stakeholders to similar activities each season. Because of steady and consistent messaging, we are regularly approached by farmers and land owners who are interested in using urine in other areas of Vermont and surrounding states. We presented results of initial field trials at the Brattleboro Agricultural Advisory Committee in February of 2013. In 2014 we will meet again with this committee and local farmers will again be invited to follow this third season closely. Site visits to the three participating farms will be encouraged. We will submit an article to the Vermont Grass Farmers Association (VGFA) newsletter.

    The Urine Nutrient Reclamation Project has been featured in two Vermont Public Radio spots. A segment filmed by Vermont Public Television crew will air in the spring of 2014. Project results will be posted on our website at www.richearthinstitute.org. We also maintain a Facebook page and have an email newsletter disseminated to over 500 people. REI is invested in making urine reuse a viable and recognized solution. We will focus on ensuring that the project is exhaustively documented to facilitate replication, and that resulting agricultural recommendations are offered to farmers through multiple channels.

    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.