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ARS Home » Northeast Area » University Park, Pennsylvania » Pasture Systems & Watershed Management Research » Research » Publications at this Location » Publication #308907
Title: Determination of particulate matter emissions from cattle feedlots using windtrax and flux-gradient technique

Author
item Bonifacio, Henry
item MAGHIRANG, RONALDO - Kansas State University
item Trabue, Steven - Steve
item MCCONNELL, LAURA - Bayer Corporation
item Prueger, John
item BONIFACIO, EDNA - Kansas State University

Submitted to: Journal of Air and Waste Management Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/13/2016
Publication Date: N/A
Citation: N/A

Interpretive Summary: Air pollutant emissions from large beef cattle feedlots have been an important issue because of their adverse effects on human health and the environment. These air pollutant emissions include both gaseous emissions, such as ammonia, hydrogen sulfide and greenhouse gases, and particulate matter (PM) emissions. To assess the human health and environmental impacts of these pollutants, it is important to have accurate air emission rate estimates applicable for cattle feedlots. There are several approaches of measuring air emission rates from cattle feedlots and these include air dispersion models and micrometeorological methods. However, several issues arise from having various techniques that can be used in estimating emission rates. Which one is the more reliable approach? How do these techniques compare to one another in terms of their estimated emission rates? Are their determined emission rates method-specific, such that emission rates calculated by a method cannot be applied to others? This study compared two of the emission estimation methods commonly used for feedlots, namely WindTrax, an air dispersion model, and the flux-gradient technique, a widely-used micrometeorological method. Concentrations of PM10 and weather conditions were measured at a commercial beef cattle feedlot in Kansas and were used in PM10 emission rate estimation. The two methods differed in terms of their determined PM10 emission rates, with the flux-gradient technique calculating higher values in general. Changing the heights and number of heights used in estimation led to considerable differences in determined emission rates for the flux-gradient technique but not for WindTrax. Nevertheless, findings from this study suggest that conversion factors can be developed between calculated emission rates of these two methods. Air pollutant emissions from large beef cattle feedlots have been an important issue because of their adverse effects on human health and the environment. These air pollutant emissions include both gaseous emissions, such as ammonia, hydrogen sulfide and greenhouse gases, and particulate matter (PM) emissions. To assess the human health and environmental impacts of these pollutants, it is important to have accurate air emission rate estimates applicable for cattle feedlots. There are several approaches of measuring air emission rates from cattle feedlots and these include air dispersion models and micrometeorological methods. However, several issues arise from having various techniques that can be used in estimating emission rates. Which one is the more reliable approach? How do these techniques compare to one another in terms of their estimated emission rates? Are their determined emission rates method-specific, such that emission rates calculated by a method cannot be applied to others? This study compared two of the emission estimation methods commonly used for feedlots, namely WindTrax, an air dispersion model, and the flux-gradient technique, a widely-used micrometeorological method. Concentrations of PM10 and weather conditions were measured at a commercial beef cattle feedlot in Kansas and were used in PM10 emission rate estimation. The two methods differed in terms of their determined PM10 emission rates, with WindTrax calculating higher values. Between the two methods, the flux-gradient technique may be better than WindTrax in estimating emissions rates because it was less influenced by the measurement bias caused by the type of sampler used. Nevertheless, findings from this study suggest that conversion factors can be developed between these two methods so that their calculated emission rates will no longer be method-specific.

Technical Abstract: Large commercial cattle feedlots are significant sources of particulate matter (PM) emissions. This research compared WindTrax and the flux-gradient technique in estimating emissions of PM with aerodynamic diameter < 10 µm (PM10) from cattle feedlots. Meteorological conditions were measured and PM10 concentrations were profiled vertically (i.e., 2.0 to 7.62 m) at a large commercial beef cattle feedlot in Kansas from May through September 2011. Results show that between the two methods evaluated, WindTrax was least sensitive to changes in heights and number of heights used in the emission estimation, with calculated PM10 emission rates varying by up to 18% only. On the other hand, PM10 emission rates produced by the flux-gradient technique varied by almost 56% when changing either heights and/or number of heights in emission calculation. Both methods were sensitive to height settings, with their respective PM10 emission rates higher when the lowest height setting (2.0 m) was included. Calculating PM10 emission rates with the 7.62-m height led to lower estimates for the flux-gradient technique but no significant change in estimates was observed for WindTrax. As demonstrated in this study, for the flux-gradient technique, settings for the lowest and highest heights were the most critical in emission estimation; exclusion of other heights in between showed only to 2% to 6% change in calculated PM10 emission rates. In general, the higher PM10 emission rates were obtained with the flux-gradient technique. However, eliminating the lowest height (2.0 m) in the calculation and, at the same time, using a specific set of formulations for the flux-gradient technique made its calculated PM10 emission rates slightly lower (but not significantly different) than those from WindTrax. Several emission estimation methods (EEMs) can be used to determine emission fluxes of air pollutants from large area sources, including open-lot beef cattle feedlots. This research was conducted to compare two EEMs in determining PM10 (particulate matter with an aerodynamic diameter = 10 µm) emission fluxes from large cattle feedlots: (a) reverse dispersion modeling with WindTrax, a backward Lagrangian stochastic-based atmospheric dispersion model, and (b) the flux-gradient technique, a widely used micrometeorological method for estimating air emissions from open area sources. PM10 concentrations were measured at a large cattle feedlot at four heights (i.e., 2.00, 3.81, 5.34, and 7.62 m) using tapered element oscillating microbalance (TEOM) and low-volume (LV) PM10 samplers during nine 4- to 5-day intensive sampling campaigns from May 2010 through September 2011. Micrometeorological conditions were also monitored with eddy covariance instrumentation. PM10 emission rates were calculated using the two EEMs (i.e., WindTrax, flux gradient). Using TEOM measurements (n = 207 hourly values), WindTrax calculated higher (16%) but not significantly different PM10 emission rates compared with those determined by the flux-gradient method. WindTrax also calculated higher emission rates (38%) when using LV measurements (n = 33 sampling runs), but this time, PM10 emission rates were significantly different from those determined with the flux-gradient technique. For both EEMs, TEOM-based emission rates were significantly higher than LV-based emission rates; however, the effect of the sampler type was more pronounced in WindTrax than in the flux-gradient method. In WindTrax, TEOM-based PM10 emission rates were higher than LV-based PM10 emission rates by a factor of two; in the flux-gradient technique, on the other hand, TEOM-based emission rates were higher than LV-based emission rates by approximately 30%.