Grantee Research Project Results
2011 Progress Report: Towards a Verifiable Ammonia Emissions Inventory for Cattle Feedlots in the Great Plains
EPA Grant Number: R834551Title: Towards a Verifiable Ammonia Emissions Inventory for Cattle Feedlots in the Great Plains
Investigators: Ham, Jay M , Lamb, Brian , Johnson, Kristen , Pressley, Shelley N.
Institution: Colorado State University , Washington State University
EPA Project Officer: Chung, Serena
Project Period: April 1, 2010 through March 31, 2013 (Extended to March 31, 2014)
Project Period Covered by this Report: April 1, 2011 through March 31,2012
Project Amount: $499,875
RFA: Novel Approaches to Improving Air Pollution Emissions Information (2009) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Air
Objective:
The goal of this study is to use novel field measurements, new modeling approaches and feedback from stakeholders to develop and evaluate an online tool for predicting site-specific beef feedlot ammonia emissions in the Great Plains.
Progress Summary:
Much progress has been made during the second year of the project. Achievements can be categorized into several areas: (1) continued work on new instrumentation for measuring NH3 emissions from livestock, including work on low-cost techniques using passive samplers and inverse modeling; (2) survey of NH3-N isotopic signatures near feedlots and other strong NH3 sources; (3) continued work on understanding the physiochemical mechanisms affecting NH3 volatilization from feedlot pens; (4) more research on the importance of animal diet and the use of hormones and other feed additives on nitrogen excretion in cattle; and (5) expanded collaboration with stakeholders and value-added linkages to other research projects. More details on some of these achievements are presented in the "Results to Date" section. A brief description is provided here.
- A new type of conditional sampler was developed that uses Radiello passive ammonia samplers. Deployment of the cartridges is robotically controlled so that they are only exposed to air under a user-defined set of weather conditions; namely, when winds are blowing directly from the feedlot source with sufficient velocity for turbulent flow. When multiple samplers are deployed at a feedlot, results reveal NH3 hot spots. The operator can then target those areas for NH3 reduction management practices. Furthermore, data can be used with inverse models to estimate NH3 emissions and improve the overall livestock NH3 inventory (i.e., support the development and verification of the online software tool).
- A study was conducted in the summer of 2011 to survey the nitrogen isotopic signatures at feedlots, dairies and other strong NH3 along the front range of Colorado. These results showed that most livestock operations have very similar isotopic fractionation. The isotopic results from fertilizer application and wastewater treatment plants were similar. Thus, isotopes may have limited value when attempting to identify livestock sources contributing NH3 to a region or air mass. However, results may have value in determining long distance transport of NH3; specifically, the residence time of NH3 in the air masses that accumulate on the eastern flank of the Rocky Mountains.
- Our own studies and the results from other research groups suggest that most NH3 from beef feedlots is lost rapidly to the air from the fresh urine patches on the pen surface (the exception might be under cold winter conditions). Thus, the key to estimating NH3 emissions hinges on determining how much N is excreted and accurately modeling the physicochemical processes that govern NH3 volatilization from the urine patches on the soil surface. Work continues in both these areas. As would be expected, simulation shows volatilization is very sensitive to temperature and pH, the former requires simulation of the surface energy balance and the latter requires an accurate submodel of urea hydrolysis and surface N chemistry (especially CO2 pH interactions). However, its not clear how much detail should be included in the modeling effort linked to the objective of this project. Recall, the central goal is to create an online tool for estimating site-specific emissions that can be used for EPA NH3 reporting. Thus, the use of a simple NH3 volatilization potential equation (e.g., Ham, 2010) that is scaled based on (a) animal diet, (b) location/weather, and (c) manure management practices seems like a tractable solution.
- The role of animal diet in NH3 emissions from feedlots cannot be overstated. The crude protein in the diet has a large impact on excretion and N emissions (Galles et al, 2010). Furthermore, feed additives and implants that alter N use efficiency (and excretion) must be considered. Survey work is under way to better quantify the typical feedlot diet and the prevalence of feed additives in the ration.
- This project benefits greatly from collaboration with stakeholders and linkages to other research projects involving NH3 losses from livestock. Collaboration with the Colorado Livestock Association is expanding, and new feedlots have agreed to cooperate (one in southern CO and one in the NE CO). Given the importance of site-to-site variation, it's crucial that the online tool is developed using data from multiple operations located in different environments.
Ammonia emissions from feedlot pens will be measured using multiple techniques at each site. The tower-based relaxed eddy accumulation (REA) system that uses a cavity ring-down NH3 analyzer will be considered the standard. However, recent research on non-orthogonal sonic anemometers suggests that most flux measurements made using eddy covariance and related techniques (e.g., REA) may be underestimating emissions by 11 to 15%. Thus, fluxes will also be estimated using inverse modeling and data from the new passive conditional samplers. A long-path laser may also be used to make spatially integrated measurements of NH3 across the feedlot. The laser data will be used to estimate flux using backward lagrangian stochastic modeling, while the passive sampler results will be used in a 3-D version of the advective diffusion model in backwards mode. Agreement or lack thereof among the different flux measurement techniques will help quantify uncertainty. Monte-Carlo techniques can be used to quantify uncertainty in the 3-D inverse modeling, while first order error analysis can be used to place error bars on the REA flux data.
More time will be invested in quantifying cattle feedlots diets and measuring the chemical properties of the feed where the field studies are being conducted. Feeding records are being obtained from both large and small feedlots in CO and KS. These results will help quantify the range of crude protein in the diet. Also, the prevalence of feed additives, hormonal implants and sub therapeutic antibiotics will be examined. These findings will help develop a more accurate profile of N consumption, N efficiently, and N excretion that is central to developing an accurate NH3 emissions tool. Results will insure that the user of the tool will be asked the proper set of question (inputs) so that the diet can be characterized.
Results from Year 1 and 2
Effect of dietary crude protein on NH3 emissions
The crude protein level in livestock diets is perhaps the most important management factor affecting NH3 losses from cattle feedlots. Unfortunately, little field data are available. Thus, a field study (partially supported by this grant) was conducted that showed reducing crude protein levels can lower NH3 losses from the pen surface by 20 to 40% (Galles et al., 2011). This is a crucial finding because the crude protein in the diet will be a key input in the on-line NH3 prediction tool. While more work is needed, these data, along with the laboratory studies, will help develop a model to properly respond to this all-important input.
A review of the literature showed that the use of feed additives is more widespread than expected and could have a significant effect on N use efficiency and excreted N. If certain feed additives are removed from the market for human health reasons, it is likely that an unintended consequence will be increased NH3 losses to the atmosphere from feedlots. As part of another research project, we are conducting a life cycle assessment (LCA) of beef production that will further demonstrate the complexity of this issue. Regardless, the software tool being developed for this project must include the impacts of feed additives and implants so that it can properly reflect future changes in feed chemistry that might be impacted by regulation.
Modeling
The mosaic model of Ham (2010) has provided some key insights:
- There are likely significant regional differences in NH3 losses from cattle feedlots caused by differences in climate. Ammonia losses from feedlots in northern CO may be 20 to 25% less than a similar feedlot near Amarillo, TX.
- Because NH3 volatilization is very dependent on temperature, accurate simulation of the surface energy balance is essential.
- As suggested by field research, most of the NH3 losses from feedlots during warm conditions occur from fresh urine patches in the pen. However, during the winter, there can be a significant build up of nitrogen on the surface which then creates a large pulse of NH3 losses when conditions start to warm in the spring. This process is more significant in northern areas (NE CO) as compared to southern feedlots (TX Panhandle).
- Developing feedlot specific (cattle manure) equations for the Henry's law constant and the equilibrium constant are essential for accurately simulating NH3 volatilization.
Data suggest that the complexity of NH3 volatilization at the pen surface may make the use of very detailed soil-air exchange models difficult to implement for the current project (i.e., developing the online NH3 tool). Thus, the NH3 potential model (batch reactor model), while still very mechanistic, is the appropriate level of detail given the inputs that can be easily provided by the user. Note, discussions with feedlot managers suggests that inputs to the model must be very easy to access (i.e., keep it simple).
Instrumentation and Measurement
- The time response of the ring-down cavity NH3 analyzer has been evaluated in the lab is and proved adequate for the REA design. However, using the analyzer in dusty environments like feedlots is challenging and the design of the air inlets is critical. An impactor plate system has been designed for testing.
- New collaboration with a research group in France is enhancing the inverse modeling effort. Data from both the ring-down analyzer and a new conditional passive samplers are being used to estimate NH3 losses from manure composting areas using the FIDES-3D model. This will provide yet another form of QA/QC for the project.
- Much progress was made on developing the passive conditional samplers that are deployed in a multimodal wireless network on the periphery of livestock operations. Using a weather based sampling protocol allows these units to both identify NH3 hot spots within feedlots and help quantify emissions via inverse modeling. Below is an example from a large commercial dairy showing the two week time-averaged concentrations of NH3 when winds, from the direction of the operation, were at speeds greater than 1.4 m/s. Studies at feedlots are underway in the summer of 2012.
- Studies of N isotopes showed little variation in N fraction among feedlots and diaries.
Future Activities:
The next 12 months of the project will focus on field measurements of NH3 emissions using both tower-based approaches and the new conditional passive samples/inverse modeling approach. The flux measurements are a continuation of last year's described activity. New efforts will be made to survey feedlot diets and better incorporate these findings into sub models of potential NH3 emissions for use in the software tool. The final goal will be to generate the first version of the software tool for estimating emissions (i.e., the tool to be used by feedlot owners and managers).
Field Studies
- Continue to refine the hardware and software for the tower-based NH3 REA system in the laboratory. These activities are occurring simultaneously at both CSU and WSU.
- In the fall of 2012 and spring of 2013, deploy the tower-based system at commercial feedlots in northern and southern CO. Conduct QA/QC by comparing NH3 fluxes measured with the REA technique to simultaneous estimates made using inverse dispersion modeling. A long path laser system and newly developed conditional passive samplers will be co-deployed with the REA tower to provide inputs to the inverse models.
- Conduct face-to-face interviews with multiple feedlot nutritionists in CO and KS to better quantify typical feedlot diets at large and small operations in the High Plains.
Laboratory Studies
- Intact soil cores will be collected from the pens adjacent to the tower during the field studies in CO. Ammonia emissions from these samples will be evaluated in the lab under controlled conditions using the chamber systems described by Galles, et al. (2011). Results will help determine how factors like ionic strength, temperature and other physicochemical factors affect the volatilization process.
- The same samples will be used to evaluate urea hydrolysis, especially at lower temperatures.
Modeling
- Results from the field and lab studies will be used to refine the model of Ham (2010) and work toward an operational form of the software tool for predicting site-specific feedlot emissions. It is anticipated that full testing and roll-out of the software tool will extend beyond the 36-month duration of the project. Thus, a 12-month no-cost extension will be requested.
- Efforts will be made to incorporate a web-based historic-weather retrieval system into the software tool. This may require that we restrict the first version of the model to the High Plains region (an area that accounts for about 80% of the feedlots).
Journal Articles on this Report : 1 Displayed | Download in RIS Format
Other project views: | All 11 publications | 2 publications in selected types | All 2 journal articles |
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Type | Citation | ||
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Galles K, Ham J, Westover E, Stratton J, Wagner J, Engle T, Bryant TC. Influence of reduced nitrogen diets on ammonia emissions from cattle feedlot pens. Atmosphere 2011;2(4):655-670. |
R834551 (2010) R834551 (2011) R834551 (Final) |
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Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.