Value-added products from urine: Enriched compost and stabilized liquid fertilizer

Project Overview

Project Type: Partnership
Funds awarded in 2015: $14,833.00
Projected End Date: 12/31/2017
Region: Northeast
State: Vermont
Project Leader:
Kim Nace
Rich Earth Institute
Abraham Noe-Hays
Rich Earth Institute

Annual Reports


  • Agronomic: grass (misc. perennial)


  • Crop Production: fertigation, fertilizers, nutrient management, organic fertilizers
  • Education and Training: demonstration, on-farm/ranch research, participatory research, technical assistance
  • Natural Resources/Environment: other
  • Soil Management: composting, organic matter
  • Sustainable Communities: local and regional food systems

    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. 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 third 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’s request for a SARE partnership grant is to expand this project, further decreasing capital and labor costs to farms using urine fertilizer by incorporating the urine into existing on-farm composting activities.

    Project objectives from proposal:

    Urine recycling could shift our agricultural practices from a linear, unsustainable use of nutrient resources into a sustainable, closed-loop nutrient cycle. Previous research by the Institute has shown that urine is an effective fertilizer for hay, and field tests in Germany and Sweden have proven that urine-based fertilizer is suitable for growing grains.

    We propose to test whether composting can transform urine into a fertilizer with better handling, storage, and application characteristics than untransformed urine. We will test three methods: 1) co-composting urine with a high-carbon feedstock, 2) co-composting urine with a high-carbon feedstock, followed by further urine additions and augmented aeration during the curing stage, and 3) using finished compost as a nitrification medium for transforming urine into a stabilized liquid product.

    These strategies for converting urine into compost or a stable liquid fertilizer will transform the ammonia into nonvolatile nitrate or organic nitrogen, while driving off a portion of the water through evaporation. Costly sealed tanks will no longer be needed for storage, and the product will be 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.


    The project will produce and evaluate new fertilizer products using urine collected through the Rich Earth Institute's ongoing Urine Nutrient Recycling Program. These products will include urine-enriched compost and stabilized liquid fertilizer. The project will be facilitated by a redesigned urine pasteurizer with greatly increased capacity. The project will also include a continuation of field trials using liquid urine to fertilize hay. Work will take place on two farms in Brattleboro, Vermont, with farmer partners who have experience using urine-based fertilizer. Whetstone Valley Farm will be the site of the compost trials, while Fair Winds Farm will supply composting feedstocks and perform additional liquid-urine field testing.

    All third-party analysis will be performed by UVM's Agricultural and Environmental Testing Lab, TestAmerica Labs, or a similarly qualified laboratory.

    Composting trial:

    Composting will occur in two purpose-built, 5' x 5' x 4' covered composting bins. The bins will incorporate controlled aeration and a network of sensors recording composting conditions throughout the piles in real time. Bins will be filled with a high-carbon feedstock blend, the composition being determined by the results of the current SARE-supported benchtop composting trial. The total NPK, percentage dry matter, C:N ratio of the feedstock blend, and total NPK of the urine will be determined by third-party testing. Sanitized urine will be added to the high-carbon feedstock using drip irrigation tape to initiate thermophilic composting. The quantity to be added will be based on calculations to achieve an initial C:N ratio of 30:1, with possible adjustment based on the benchtop trials, due to the immediate availability of nitrogen in urine.

    Temperatures will be monitored using nine digital temperature probes placed in each pile. Probes will be distributed in a two-dimensional grid, with vertical positions in the top, middle, and bottom layers of each pile and horizontal positions at the core, periphery, and a midpoint.

    Piles will sit on a concrete slab and have waterproof liners to collect all leachate, which will be pumped into storage containers. Bin walls will be non-permeable to simulate conditions within a full-scale vessel or large windrow. Oxygen and ammonia gas concentrations throughout the piles will be monitored and active aeration employed via blower and buried diffusion pipes to ensure that oxygen levels exceed 5%. Compost moisture and pH levels will be tested regularly by core sampling and moisture maintained at 50-60% by addition of urine using drip irrigation tape. Bins will be treated identically throughout the thermophilic phase until internal temperature drops to 30°C. Then Bin 1 will continue to receive aeration to maintain 5% oxygen, while Bin 2 will receive increased aeration to facilitate evaporation and allow further urine addition. Aeration rate will be increased until it begins to interfere with reliable moisture content control or cause an elevation of pH. Urine will be added to each pile as needed to maintain 50-60% moisture.

    Nitrified liquid fertilizer production:

    A third bin at Whetstone Valley Farm will be test the effectiveness of trickling sanitized urine through compost to stabilize it and nitrify the ammonia fraction. In the spring, the Bailey family will empty finished compost from their livestock manure shed. Up to four yards of this compost—from horse manure, wood shavings, and small amounts of other organic material—will be added to the bin. Coarse wood chips may be added to improve the free airspace of the compost. Urine will be added to the bin using drip irrigation tape to evenly wet the compost. All leachate will be collected and tested periodically by a third-party lab for nitrate, nitrite, ammonia, and pH. More frequent onsite pH testing will be used as a proxy for the nitrate-N:ammonia-N ratio. The active aeration rate will be adjusted to keep oxygen levels above 10%, encouraging nitrification and discouraging denitrification. A grid of temperature probes will perform continuous temperature measurements, as in the other bins. Additional urine will be added at a rate to be determined to most closely meet the following targets: approximately 1:1 ratio between nitrate-N and ammonia-N in leachate, pH of leachate neutral to slightly acidic, compost moisture levels low enough to maintain an aerobic environment throughout (evidenced by absence of odors characteristic of anaerobic conditions in compost core samples.) Urine will be added at the maximum rate that conforms to these targets, and the resulting leachate will be pumped into a storage tank for collection and analysis. The urine feedstock and the resulting leachate will both be third-party tested for total-N, ammonium-N, potassium, phosphorus, electrical conductivity, and pH. Compost will be submitted for UVM's standard compost analysis. If additional funding can be secured, samples of urine before and after nitrification treatment will be sent to the Institute's partners at University at Buffalo for pharmaceutical analysis, to determine the degree to which the process removes 14 common pharmaceuticals.

    Continued field trial:

    Farmer partners at Fair Winds Farm will perform a fourth year of field trials, replicating the 2014 experiment under new field conditions and expanding the data set that compares hay yield from diluted vs. undiluted urine application.


    An analysis of the three treatment methods will include the efficiency at which ammonia in urine is assimilated into compost or stabilized leachate (as opposed to being lost to volatilization), the total NPK levels in the finished product, any practical difficulties in executing each treatment, and the amount of energy consumed by the ventilation blowers. Other differences in compost quality revealed by third-party testing will be noted. The report will include an assessment of which of these three treatment methods is most promising for large-scale application. The report will indicate how well it achieves the project goals of producing a fertilizer product that is more concentrated, less costly to store, and easier to apply than the untransformed urine. If data from the field trials require changes to previous conclusions about the effect of urine dilution on hay yields, it will be discussed.


    March 2015:

    The new urine pasteurizer will be tested by Institute staff, and sufficient urine to begin the composting trial (already onsite) will be pasteurized and returned to storage. Samples of the pasteurized urine will be sent out for coliform and nutrient testing at third-party labs.


    Finished compost from Fair Winds Farm and other high-carbon feedstocks will be transported to Whetstone Valley Farm by the Institute and stored under cover. The three compost bins will be built by Institute staff, in consultation with Bob Spencer, and fitted with dataloggers, instrumentation, and aeration systems, with a target

    completion date of May 15.


    Best Septic will transport urine to Fair Winds Farm, and Institute staff will train partner farmers Jay and Janet Bailey in operation of the pasteurizer. Urine will be pasteurized and samples sent out for coliform and nutrient testing. Best Septic will continue to transport urine to the two farms throughout the project period as needed to support the composting trials and continued field testing on hay.

    Institute staff will fill the compost bins with their respective media and add sanitized urine as described In the methods section. Bins 1 and 2 are expected to enter the thermophilic composting phase quickly and remain there for 8-12 weeks. Bin 3 (for mesophilic nitrification) will remain at or near ambient temperature throughout this period.


    Farmer partners will spread urine on the designated test strips and on whatever other hayfields they choose, as the first cutting schedule permits. Institute staff will assist by marking the boundaries of the test plots and measuring precise quantities of urine for application to the test strips.


    Bins 1 and 2 are expected to enter the curing stage, at which point Bin 2 will begin receiving increased aeration and additional urine inputs. If Bin 3 is producing nitrified liquid fertilizer, operation will continue unchanged. If it is not performing as anticipated, Institute staff will make adjustments to the operation regime or to the media composition for evaluation during the remainder of the experiment.

    August or September:

    Partner farmers will cut and bale hay, which will be weighed and documented by Institute staff.


    Curing of Bins 1 and 2 will continue (with further urine additions to Bin 2), and Bin 3 will continue to operate as a nitrification reactor, until moisture content, ammonia levels, or other physical characteristics indicate that the compost is cured and/or the respective process intended for each bin has reached its conclusion.

    November 2015—January 2016:

    Institute staff will sample compost and nitrified liquid fertilizer, sending samples to a third-party lab for nutrient and physical analysis, and conducting in-house Lepidium sativim bioassays. Institute staff will analyze data logs and assess performance of the compost trials.

    February—March 2016:

    In consultation with partner farmer, Best Septic Services, and Bob Spencer, Institute staff will prepare the final report documenting the results of the experiment and the practical knowledge gained in the process.


    In 2015 we will attend the Vermont Grazing and Livestock conference in January, the NOFA Winter Conference in February, the Building Energy Conference in Boston in March and the UVM Food Systems summit in June. We are already slated for a 2 session panel presentation in Boston and have submitted or will submit applications to present at the other conferences.

    In the past year, interview requests from regional, national, and international media outlets have stepped up dramatically. We have been published online in Modern Farmer magazine, National Geographic, Grist, Greenspec, Gizmodo and NPR’s The Salt. The national professional journal for urban and regional planners (Planning) and for septage haulers (Pumper) have featured our project. We have been interviewed by Vermont Public Radio, Vermont Public Television, the CBC, and the Australian Broadcast Corporation.

    Visitors from across New England and as far away as Panama, China, South Africa, Germany and Mexico have toured the test site at Fair Winds Farm. School groups from Yale, Hampshire and Marlboro Colleges visited this past summer. Almost daily unscheduled visitors arrive to see the demonstration toilet at the office of the Rich Earth Institute.

    Project results will be posted on our website at We also maintain a Facebook page and have an email newsletter disseminated to over 900 people.

    In 2015, we hope to hire additional personnel at the Institute. This support will allow us to further develop appropriate publications for distribution in order to share our results with our farming communities.

    The Rich Earth Institute is invested in making urine reuse a viable and recognized solution. We will ensure that the project is thoroughly 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.