Field Trials: We will determine relative rates of ammonia loss when urine-derived fertilizers (UDFs) are applied to perennial grass using different fertilizer preparation and application methods and under varying soil moisture and wind speed regimes. We will establish a range of conditions where UDFs can be applied with acceptable ammonia volatilization rates to enhance nitrogen retention in soils. By identifying surface application methods and conditions that minimize ammonia volatilization, we will increase the efficacy and economic benefit to grass farmers using UDFs.
On-site visits: In dialog with farmers from a diverse array of livestock farms, we will explore the best strategies and opportunities for using current or slightly modified equipment to use UDFs effectively on their farms for hay, corn, and other feed production while minimizing ammonia loss through tillage or judicious surface application. The documentation and dialogue will address fertility management practices (including use of liquid manures and digestates); equipment used; timing and weather conditions of application; and different soil management practices. The goal is to strategize with farmers the practices, tools, techniques, and critical research to make most effective use of UDFs under varying management conditions.
Our project addresses two problems: 1) nutrient pollution of waterways, and 2) the unsustainability of synthetic fertilizer. Our approach to solving both problems is to divert human urine out of the wastewater stream, reclaiming dissolved NPK and trace plant nutrients for use as agricultural fertilizer.
Ponds, lakes, and coastal estuaries throughout the Northeast are heavily impacted by nitrate and phosphate pollution caused by human activity. Much is made of nutrient pollution from agricultural sources, but wastewater is also a major contributor, and is the principal source of nutrient pollution in some heavily populated watersheds in the Northeast. Fertilizer is expensive for farmers, and prices are unpredictable, threatening farms’ financial viability. Nitrogen is tied to the volatile price of unsustainable fossil fuels. Phosphate is a finite resource, and the Global Phosphorus Research Initiative predicts a shortage of quality rock phosphate within 40 years.
Human urine contributes 70% of the nitrogen and 50% of the phosphorous in wastewater. Most of these nutrients pass through treatment works and into surface waters where they cause pollution. Diverting urine from the wastewater stream and recycling it into fertilizer production would eliminate pollution from waterways, and satisfy 25% of the entire U.S. NPK fertilizer demand.
Previous SARE-funded research by the Rich Earth Institute, (which operates the nation’s first community-scale urine recycling program in Brattleboro, Vermont) has demonstrated in multi-year trials that sanitized urine can effectively replace synthetic fertilizer in hay production when applied under ideal conditions. However, nearly all the nitrogen in urine rapidly converts into ammonia, which is prone to loss by evaporation if applied under non-ideal conditions. Although research exists on ammonia loss from animal manures, there are currently no research-based guidelines on acceptable methods and conditions for surface application of urine derived fertilizer (UDF) on hay.
Our farmer partners, who have seen dramatic yield improvements as a result of UDF, are enthusiastic about continuing to use it. They have expressed strong interest in obtaining data on nitrogen retention in soil over time and best management practices for maximizing the benefits of UDF. Most grass farmers responding to our survey (described in final report SARE ONE14-218) reacted positively to the idea of using UDF. 75% said they wanted more information about fertilizer benefit and 58% wanted to know more about the equipment required to use this fertilizer.
In addition to high-ammonia, sanitized urine, the Institute has also developed several forms of stabilized product that can now be tested to determine optimal fertilizer formulation, application method, timing, weather and soil conditions that are best suited to minimize loss of nitrogen to the atmosphere.We propose to:
1) conduct field trials to quantify ammonia loss from urine-derived fertilizers applied to perennial grass, under a range of environmental conditions and using different UDF products
2) conduct site visits with a diverse array of farmers to a) develop effective strategies for incorporation of urine-based fertilizers into current farm operations, and b) conceptualize the tools, techniques and further research needed to support this potentially transformative practice.
Urine-derived fertilizer (UDF) has a long and established record as a safe and effective replacement for synthetic fertilizer (WHO, 2006) on a wide variety of grains, fruits, and vegetables. Numerous treatment methods are available to inactivate pathogens, including the pasteurization method permitted in Vermont and employed by the Rich Earth Institute. The question of pharmaceutical presence in urine is often raised; our research to date has shown that although pharmaceuticals are present in urine, a person would have to eat nearly a million pounds of lettuce fertilized with urine to receive a single dose of any pharmaceutical (Mullen, et. al., 2015). Even so, to avoid any issues with public perception our efforts focus on fertilization of animal feed crops.
The Institute has conducted four years of field trials using urine-derived fertilizer on hay (SARE ONE13-188, ONE14-218, ONE15-244, and an earlier 2012 trial). Two trials on very moist sandy loam soils both showed strong positive yield response comparable to synthetic fertilizer controls, while trials on drier and sandier soils showed strong response one year and poorer response on the following year.
For urine-derived fertilizer to be effectively utilized in hay production, we believe that the most important factor to control is the loss of nitrogen through ammonia volatilization. This is an issue with other nitrogen-rich fertilizers; ammonia volatilization losses from surface-applied synthetic urea can exceed 60% (Horneck et al., 2011), while losses from animal manure can exceed 90% (Jokela and Meisinger, 2008). These losses can be virtually eliminated through immediate incorporation, such as by simple tillage in row crops such as corn, but subsurface incorporation on grasslands cannot be done without specialized equipment. To make urine-derived fertilizers more accessible to hay producers, guidelines are needed for effective surface application.
Manure characteristics affecting ammonia volatilization include solids content, NH 4 -N content, and pH, with increases in each characteristic leading to increased risk of volatilization (Jokela and Meisinger, 2008). Our own testing shows that nearly all the nitrogen in sanitized urine is in the ammonia/ammonium form, (all urea having hydrolyzed to ammonia,) and the pH is around 9, near ammonia’s pK a of 9.25. Due to these two factors, unincorporated sanitized urine is extremely prone to volatilization. Fortunately the solids content of urine is very low, so urine is more able to self-incorporate into soil by soaking in, compared to manure slurries which pool on the surface and remain exposed. Furthermore, our custom applicator with trailing hoses mimics the ammonia-conserving technique of applying liquid manure in discrete bands (Pfluke et al,2011). How these opposing factors balance out when UDF is applied to perennial grasslands is unknown, as are the specific effects of environmental factors and fertilizer application methods.
Since 2015, the Rich Earth Institute has also conducted trials producing urine-enriched composts. Results indicate that co-composting urine with leaves has the benefit of binding about 65% of the nitrogen from urine into a solid form with an elemental N:P ratio above 10, and safe ammonia and salinity levels (SARE ONE155-244 final report). Limitations of this method include the 35% of nitrogen that is lost during composting, and the requirements for leaf feedstock, compost-making/application equipment, and labor. Because composting will not be suitable for all farms, we believe it is also important to develop best practices for surface application of liquid urine-derived fertilizers.
In collaboration with a multidisciplinary team coordinated by the University of Michigan and funded by an NSF grant, the Rich Earth Institute is developing and testing new UDF production techniques while conducting social research about public perception and attitudes. One of the new UDF formulas is an acid-stabilized urine concentrate which contains most of its nitrogen in urea form. Our hope is that that this fertilizer will absorb fully into the soil before the urea can degrade into ammonia, greatly reducing volatilization. An alternate alkali stabilization method (Randall, 2016) also maintains nitrogen in urea form, but at a high pH. This product also seems likely to initially absorb into the soil with low ammonia losses, but the product’s high pH could drive later volatilization once soil urease degrades the urea into ammonia.
The potential for urine-derived fertilizer production is immense. With 54.5 million people living in the Northeast SARE region, each producing 4 kg of nitrogen annually in their urine annually (Vinnerås, 2002), there is a maximum potential to source 218 million kg of nitrogen fertilizer each year, (not to mention P, K and trace nutrients,) which would nearly meet the region’s approximately 280 million kg demand for N fertilizer. (EPA, 2017)
The experiment involves conducting NH3 volatilization trials under differing field conditions to determine the effect of different strategies for controlling ammonia loss following urine-derived fertilizer (UDF) application. Strategies to be tested include banding vs. broadcast application of UDF, application of UDF under varying soil moisture and wind conditions, and pre-processing of UDF to reduce the concentration of volatile N species. All trials will include a no-fertilizer control, and pre-processed UDF trials will include a synthetic urea treatment.
Field trials will take place on two farms growing hay: Fair Winds Farm (very sandy soil), and Whetstone Valley Farm (higher clay content), both in Brattleboro, Vermont. All fertilizer will be applied at a rate of 50# N/acre. Fertilizer treatments will be applied after harvest of hay, to subplots that will be immediately covered with vented ammonia capture chambers. Treated areas will be separated by 1 m buffer zones. Subplots will be arranged in a randomized block design.
There are four discrete trial designs, articulated in the attached tables, testing the effect of soil moisture, application method, urea stabilization method, and wind speed on ammonia volatilization. If possible, we will replicate each trial on both farms, but this is ambitious and may not be attainable given the time allotted. The soil moisture trial will be performed on both farms, and the other three trials will be performed on at least one farm, and replicated on a second farm as time allows. If ammonia values from no-fertilizer control plots are negligible in initial trials, the number of control replicates may be reduced in subsequent trials to allow more trials to be performed.
Each ammonia gas capture chamber consists of an ammonia trap inside an enclosure. The enclosure is a clear plastic box measuring approximately 50 cm x 40 cm x 35 cm high, placed open-side-down over the portion of the test plot from which ammonia is to be captured. Each enclosure will be perforated with a still-to-be-determined pattern of holes to facilitate gas exchange. Inside the enclosure is placed the ammonia trap, made up of an open plastic container holding 250 mL of 0.15 N H2SO4, and a 40 mm x 40 mm x 15 mm 12V (1 W) electric fan that is supported just above the container, blowing down onto the surface of the acid. Two methods were used to measure the amount of ammonia absorbed by the trap during this test: colorimetric quantification of ammonia concentration using the Hach High Range Ammonia Nitrogen Test ‘N Tube method, and titration using H2SO4 to determine the amount of acid neutralized by NH3.
In preparation for deploying them to the field, we tested the capture chambers to determine the percentage of total volatilized NH3 captured by the acid trap at high rates of volatilization. First, the capture chambers were set up indoors on a bare table, into which were placed open trays containing 1 g ammonia in 1% or 5% solution. The ammonia was allowed to evaporate for 24 hours, at which point negligible alkalinity was measured by titration of the remaining solution with 0.3 N H2SO4, which confirmed full volatilization of the ammonia in this time frame. Then the same test was repeated, but with the capture chambers set up outdoors on mown turf grass. The colorimetric analysis of samples from the ammonia traps was conducted in our own lab in order to get immediate results in case adjustments to the enclosure and recalibration were required.
Unfortunately, the colorimetric ammonia quantification produced inconsistent results that we were not able to resolve immediately. We will be working to resolve this issue before the 2019 field season.
In response to the difficulty with the colorimetric method, we tested a backup method for indirectly quantifying captured ammonia: calculating the quantity of acid neutralized in the trap during the capture of ammonia. To do this, we recorded the volume and concentration of acid that was used to fill the trap before it was placed in the enclosure, in order to quantify the total amount of acid in the trap. After the trap was exposed to ammonia, we determined the volume of the trap contents again and titrated a 10 mL subsample with 0.01 M NaOH, to determine the total quantity of acid remaining. This allowed us to calculate the moles of acid (H+) consumed during the experiment, which equals the moles of ammonia captured, assuming no other sources of alkalinity entered the trap. This method appeared to be more consistent than the colorimetric method, and if we are unable to resolve the issues with the colorimetric method we will use this method as our primary method, with third party colorimetric testing of some samples for confirmation.
These issues delayed calibration of the ammonia capture enclosures long enough that we were unable to conduct the field trial stage of the experiment in 2018. In 2019 we will continue to refine and test our ammonia capture chambers, proceeding to the field trial when we are confident of the repeatability and accuracy of our measurements.
The following are the methods we will use for the field trial itself:
Due to the very rapid ammonia volatilization rate from liquid manure (and presumably urine), with the great majority of ammonia loss occurring within the first two days (Meisinger and Jokela, 2000), chambers will be left in place for 4 days–except for the stabilized UDF trial, in which chambers will be monitored for 14 days. Interior and exterior soil and air temperatures will be electronically logged.
Also prior to the trial, surface soils (0-10 cm) on each farm will be characterized using the UVM AETL standard fertility test and soil texture test (%sand/silt/clay by hydrometer) for composite samples.
We will attempt to initiate the soil moisture trials during a window of warm, dry weather in order to generate soil moisture conditions significantly below field capacity (moisture level 1). Moisture levels 2-4 will be created by irrigation at least 24 hours prior to fertilization, with the target of field capacity for level 4. If the weather does not allow soil to dry significantly, the soil moisture treatments will be replaced by post-fertilization irrigation treatments of 0.5” at varying periods after fertilization to simulate rainfall.
This component of the project aims to assess the feasibility of application and physical incorporation of urine by Vermont farmers most likely to benefit from such application in the near term – i.e. farmers who raise feed corn, hay, forage grains or pasture. Through a series of on-site meetings comprised of observations and dialogue with 7-10 such farmer participants, we
will conceptualize the best practices, tools and techniques needed to effectively apply urine-based fertilizers, and explore options for converting current equipment to allow urine-derived fertilizers to be included in their nutrient-management plans.
The farms to be included represent a diversity of farm types located in Southern and CentralVermont based on farm size, crops grown, type of livestock, and management styles including conventional, transitioning, certified organic, and other “ecological” approaches. Our focus on applications on crops used for animal feed is based in part on our current social research which suggests that this may be more readily acceptable by the public than use on crops for human consumption (at this time).
These visits, anticipated to require approximately 90 minutes, and to be conducted in late winter/early spring of 2019, will include observation and documentation of current soil fertility management practices; equipment used; and application methods for synthetic fertilizers, organic amendments, manures, liquid manures and digestates. In addition, the visits will involve recorded dialogue with farmers concerning the potential for incorporating urine-based fertilizers in their management plans using existing or slightly modified equipment. These conversations will also address farmer observations and beliefs about best timing and weather conditions for application of nitrogen-based fertilizers; the potential obstacles farmers foresee in using UDFs (including social issues such as customer perception, and best methods for addressing these); recommendations and ideas for equipment modification; and suggestions for additional research, such recommendations for soil health parameters that could be evaluated in future trials.
At this point, an extensive list of both quantitative and open-ended questions have been developed from topics and ideas raised in previous farmer surveys (SARE ONE14-218), along with guidelines for dialogue at each site visit, with a focus on allowing each site’s specific characteristics and each farmer’s ideas to be documented, while creating a consistent format for each visit following standard qualitative research procedures.
Following these visits, the observations, documentation and recorded dialogue will be comprised into a summary report, which will be shared with participating farmers for further feedback. The report will then be revised for wider distribution to farmers who are interested in potential application on their farms.
Environmental Protection Agency. Commercial Fertilizer Purchased. 2017. https://www.epa.gov/nutrient-policy-data/commercial-fertilizer-purchased
Horneck, DA; Holcomb, J; Sullivan, D; and Clough, G. Ammonia Volatilization in Grass Forages. 2011. Proceedings, Western Alfalfa & Forage Symposium, Las Vegas, NV, Dec. 11–13.
Jokela, WE: and Meisinger, JJ. 2008. Proc. of the 2008 Wisconsin Fertilizer, Aglime & Pest Management Conference. Vol. (4)
Meisinger, J.J.; and Jokela, WE. 2000. Ammonia Volatilization From Dairy and Poultry Manure. Managing Nutrients and Pathogens from Animal Agriculture. Natural Resource, Agriculture, and Engineering Service, PO Box 4557, Ithaca, NY 14852-4557. www.nraes.org
Mullen, RA; Noe-Hays A; Nace, K; Lahr, R; Goetsch, H; Love, N; Wigginton, K; and Aga, DS: Analysis of Pharmaceuticals in Food Crops Grown in Urine and Struvite Fertilized Soil by Liquid Chromatography-Tandem Mass Spectrometry. 2015. Poster presented at American Chemical Society Conference, Boston, MA. August 16-20.
Pfluke, PD; Jokela, WE; and Bosworth SC. 2011. Ammonia volatilization from surface-banded and broadcast application of liquid dairy manure on grass forage. J Environ Qual. 2011 Mar-Apr;40(2):374-82.
Randall, DG; Krähenbühl, M.; Köpping , I; Larsen, TA; and Udert, KM. 2016. A novel approach for stabilizing fresh urine by calcium hydroxide addition . Water Res. May 15: 95: 361-269.
Vinnerås, B. Possibilities for Sustainable Nutrient Recycling by Faecal Separation Combined with Urine Diversion. 2002. PhD Thesis, Swedish University of Agricultural Sciences, Dept. of Agricultural Engineering, Uppsala, Sweden.
World Health Organization. Guidelines for the safe use of wastewater, excreta and Greywater Vol. 1 Policy and regulatory aspects. 2006. Geneva, Switzerland.
Education & Outreach Activities and Participation Summary
None yet. These activities will happen in the coming year.