Progress 02/01/04 to 01/31/08
Outputs OUTPUTS: Cattle feedlots are one of the largest sources of atmospheric ammonia in the Great Plains. Ammonia can have a detrimental effect on the environment and efforts are underway to obtain an accurate ammonia inventory and develop methods for reducing ammonia emissions. To accomplish these goals new instrumentation is needed to measure ammonia fluxes and emission factors from cattle feedlots. A micrometeorological technique called relaxed eddy accumulation (REA) was adapted for measuring NH3 and aerosol NH4+ fluxes (jointly referred to as NHx). REA requires independent sampling of up-moving and down-moving eddies based on the real-time direction of vertical wind speed. An REA sampling system was designed around a pair of ChemComb 3500 Speciation Sampling Cartridges whose main feature is a series of high capacity honeycomb denuders. Breakthrough curve studies of the ChemComb showed it had a capacity to trap over 1800 microgram of NH3, a capacity that would allow continuous operation for up to 24 hours at a cattle feedlot. An REA control system operating at 20 Hz used a pair of high speed valves and a recirculating air handling configuration to discretely sample up-and down draughts of air into two denuders. A time-averaged approach to REA was developed theoretically and tested experimentally at the Kansas State University Beef Research Center, Manhattan, KS, and at 30,000-head commercial feedlot in central Kansas. Differences in the NH3 concentrations between up- and down-moving eddies were between 500 and 1200 ppb when fluxes of NH3 were between 45 and 110 microgram m2 s-1. Aerosol NH4+ represented less than 1% of the total NHx flux. When compared to the pen nitrogen balance, ammonia emissions were, on average, 46 to 54% of the feed nitrogen. Nitrogen intake for feedlot cattle is often between 200 and 240 g/head/day. Thus, a 30,000 head feedlot could be emitting on the order of 3000 kg of nitrogen per day or over 6,600 lbs of ammonia nitrogen per day. PARTICIPANTS: Jay Ham, Cooperating Feedlot Managers TARGET AUDIENCES: Cattle Feedlot, Livestock Industry Groups, Regulators PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts Obtaining good ammonia emissions factors for feedlots is critical because the industry is under increasing environmental scrutiny. Unfortunately, estimating long-term NH3 losses from feedlots is challenging because of the complex chemistry, physics, meteorology, and biology that governs the ammonia volatilization process. Furthermore, the conversion of NH3 gases to secondary aerosols complicates air sampling. This research provides new and confirming evidence that ammonia emissions are typically 45 to 55% of the nitrogen delivered to feedlot pens. These rates are slightly lower than those reported by others using less direct techniques. Because feedlot cattle across the High Plains are fed very similar diets and the number of cattle on feed at any time is known (part of the agriculture statistics service) this research should allow improved regional estimates of ammonia losses from cattle feedlots. Also, the measurement technology developed in this research could be used to test methods for reducing feedlot ammonia emissions. Given that cattle feedlots are a several billion dollar industry in Kansas, any research that helps this industry respond to environmental concerns and take proactive measures to avoid potentially costly regulation could have substantial economic benefits.
Publications
- Ham, J.M., and K.A. Baum. 2007. Measuring Ammonia Fluxes from Cattle Feedlots Using Time-Averaged Relaxed Eddy Accumulation. International Symposium on Air Quality and Waste Management for Agriculture. Publication date 16, September 2007 ASABE Publication Number 701P0907cd
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Progress 01/01/07 to 12/31/07
Outputs OUTPUTS: Cattle feedlots are one of the largest sources of atmospheric ammonia in the Great Plains. Ammonia can have a detrimental effect on the environment and efforts are underway to obtain an accurate ammonia inventory and develop methods for reducing ammonia emissions. To accomplish these goals new instrumentation is needed to measure ammonia fluxes and emission factors from cattle feedlots. A micrometeorological technique called relaxed eddy accumulation (REA) was adapted for measuring NH3 and aerosol NH4+ fluxes (jointly referred to as NHx). REA requires independent sampling of up-moving and down-moving eddies based on the real-time direction of vertical wind speed. An REA sampling system was designed around a pair of ChemComb 3500 Speciation Sampling Cartridges whose main feature is a series of high capacity honeycomb denuders. Breakthrough curve studies of the ChemComb showed it had a capacity to trap over 1800 μg of NH3, a capacity that would allow continuous operation
for up to 24 hours at a cattle feedlot. An REA control system operating at 20 Hz used a pair of high speed valves and a recirculating air handling configuration to discretely sample up- and down draughts of air into two denuders. A time-averaged approach to REA was developed theoretically and tested experimentally at the Kansas State University Beef Research Center, Manhattan, KS, and at 30,000-head commercial feedlot in central Kansas. Differences in the NH3 concentrations between up- and down-moving eddies were between 500 and 1200 ppb when fluxes of NH3 were between 45 and 110 μg m2 s-1. Aerosol NH4+ represented less than 1 % of the total NHx flux. When compared to the pen nitrogen balance, ammonia emissions were, on average, 46 to 54 % of the feed nitrogen. Nitrogen intake for feedlot cattle is often between 200 and 240 g/head/day. Thus, a 30,000 head feedlot could be emitting on the order of 3000 kg of nitrogen per day or over 6,600 lbs of ammonia nitrogen per day.
PARTICIPANTS: Jay Ham, Cooperating Feedlot Managers
TARGET AUDIENCES: Cattle Feedlot, Livestock Industry Groups, Regulators
PROJECT MODIFICATIONS: None
Impacts Obtaining good ammonia emissions factors for feedlots is critical because the industry is under increasing environmental scrutiny. Unfortunately, estimating long-term NH3 losses from feedlots is challenging because of the complex chemistry, physics, meteorology, and biology that governs the ammonia volatilization process. Furthermore, the conversion of NH3 gases to secondary aerosols complicates air sampling. This research provides new and confirming evidence that ammonia emissions are typically 45 to 55 % of the nitrogen delivered to feedlot pens. These rates are slightly lower than those reported by others using less direct techniques. Because feedlot cattle across the High Plains are fed very similar diets and the number of cattle on feed at any time is known (part of the agriculture statistics service) this research should allow improved regional estimates of ammonia losses from cattle feedlots. Also, the measurement technology developed in this research could be
used to test methods for reducing feedlot ammonia emissions. Given that cattle feedlots are a several billion dollar industry in Kansas, any research that helps this industry respond to environmental concerns and take proactive measures to avoid potentially costly regulation could have substantial economic benefits.
Publications
- Ham, J.M., and K.A. Baum. 2007. Measuring Ammonia Fluxes from Cattle Feedlots using Time-Averaged Relaxed Eddy Accumulation. International Symposium on Air Quality and Waste Management for Agriculture. Publication date 16, September 2007 ASABE Publication Number 701P0907cd
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Progress 01/01/06 to 12/31/06
Outputs Research over the reporting period included: 1) development of new techniques to measure ammonia emissions, 2) new ways to estimate what areas of the feedlot are contributing to air samplers, 3) better estimates of the nitrogen fed to cattle in commercial operations, and 4) measurement of nitrogen movement beneath cattle feedlot pens. A new measurement technique called "Time- Averaged Relaxed Eddy Accumulation" TA REA was developed both theoretically and experimentally. That is, turbulence data collected above the feedlots were used to perform a synthetic simulation of the TA REA concept and demonstrate its potential. By using a special type of ammonia sampler called a honeycomb denuder, TA-REA permits the measurement of ammonia losses over week-long periods before the denuder cartridges must be serviced and analyzed. Thus, this technique is a viable long term approach, an important capability when studying ammonia losses where diurnal and seasons variations are
expected. Studies also showed that tower-based sensors deployed above a feedlot sample a relatively small land area. This area is called the "footprint" of the air sampler. Given the height and location of an air sampler, a method was developed to determine which cattle pens were being measured at any moment in time based on weather conditions and a GPS-measured map of the pens. A state-of-art GPS system was used to map the feedlot and determine the fraction of the total area represented by pens, feeding bunks, roads and alleys, and other structures. These results helped convert the tower-based measurements into a number representing the actual losses per unit area of pen surface. Detailed accounting of feeding records showed large site-to site variations in the amount of fecal and urine-nitrogen deposited on the pen surface per unit area. This variance was caused by differences in stocking density among sites. Soil cores were collected beneath several feedlots using a specialized
direct-push sampler. These data showed that deep-percolation of nitrogen beneath the pens was very small and a negligible portion of the overall nitrogen balance.
Impacts Animal feeding operations (AFOs) represent one of the largest segments of agribusiness in the U.S. Forthcoming regulations on ammonia could impact the size and economic viability of AFOs across the country. This research will quantify ammonia emissions from commercial feedlots, providing science based information that will help producers and regulators alike.
Publications
- No publications reported this period
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Progress 01/01/05 to 12/31/05
Outputs Detailed measurements above a commercial cattle feedlot in central Kansas showed that micrometeorological methods are acceptable for measuring gas emissions occurring from the pen surface (e.g., dust, ammonia) but are not suitable for measuring emissions from the animals (e.g., carbon dioxide, methane). Detailed measurements of air flow above a large block of pens showed that the feedlot was relatively aerodynamically smooth despite the presence of bluff bodies like fences, bunks, cattle. Progress was made on a new measurement technique that will hopefully allow near continuous measurement of ammonia losses. This technology will allow measurement of seasonal patterns and annual total losses of ammonia. Soil cores were collected in cattle pens that had been used for 20 to 45 years. Although high nitrogen concentrations were found in the first meter of the soil profile, the total quantity of nitrogen in the subsoil was negligible compared with the total amount of
nitrogen deposited on the pen surface over its lifetime. A detailed study is now underway to determine the rates of nutrient loading on the pen surface by analysis of feeding records, cattle weight gains, and rates of manure removal during pen cleaning.
Impacts Results from this study will lead to improved methods for estimating total ammonia losses from cattle feedlots in the Great Plains.
Publications
- No publications reported this period
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Progress 01/01/04 to 12/31/04
Outputs This project has been active for about 11 months. We are in the early stages of the field work. Results include: Detailed measurements above a commercial cattle feedlot in central Kansas showed that micrometeorological methods are acceptable for measuring emissions occurring from the pen surface (e.g., dust, ammonia) but may not be suitable for measuring emissions of gases from the animals (e.g., carbon dioxide, methane). Both field measurements and theoretical calculations showed that a measurement technique called relaxed eddy accumulation may have promise as a way to make continuous measurements of ammonia losses from cattle feedlots. Given that ammonia losses are often episodic or have strong diurnal patterns, a continuous record of flux would greatly improve long term estimates of annual ammonia emissions from cattle feedlots.
Impacts Results from this study will provide important science-based information to agencies that regulate ammonia as well as researchers developing best management practices to reduce feedlot ammonia emissions.
Publications
- No publications reported this period
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