William B. Faulkner

Sensitivity of two dispersion models (AERMOD and ISCST3) to input parameters for a rural ground-level area source.

Abstract As of December 2006, the American Meteorological Society/U.S. Environmental Protection Agency (EPA) Regulatory Model with Plume Rise Model Enhancements (AERMOD-PRIME; hereafter AERMOD) replaced the Industrial Source Complex Short Term Version 3 (ISCST3) as the EPA-preferred regulatory model. The change from ISCST3 to AERMOD will affect Prevention of Significant Deterioration (PSD) increment consumption as well as permit compliance in states where regulatory agencies limit property line concentrations using modeling analysis. Because of differences in model formulation and the treatment of terrain features, one cannot predict a priori whether ISCST3 or AERMOD will predict higher or lower pollutant concentrations downwind of a source. The objectives of this paper were to determine the sensitivity of AERMOD to various inputs and compare the highest downwind concentrations from a ground-level area source (GLAS) predicted by AERMOD to those predicted by ISCST3. Concentrations predicted using ISCST3 were sensitive to changes in wind speed, temperature, solar radiation (as it affects stability class), and mixing heights below 160 m. Surface roughness also affected downwind concentrations predicted by ISCST3. AERMOD was sensitive to changes in albedo, surface roughness, wind speed, temperature, and cloud cover. Bowen ratio did not affect the results from AERMOD. These results demonstrate AERMOD’s sensitivity to small changes in wind speed and surface roughness. When AERMOD is used to determine property line concentrations, small changes in these variables may affect the distance within which concentration limits are exceeded by several hundred meters.

Comparison of Dispersion Models for Ammonia Emissions from a Ground-Level Area Source

Dispersion models are important tools for determining and regulating pollutant emissions from many sources, including ground-level area sources such as feedyards, dairies, and agricultural field operations. This study compares the calculated emission fluxes of ammonia from a feedyard in the Texas panhandle using four dispersion models: Industrial Source Complex Short Term Version 3 (ISCST3), AERMOD-PRIME, WindTrax, and AUSTAL. ISCST3 and AERMOD are Gaussian plume models, while WindTrax and AUSTAL are backward and forward Lagrangian stochastic models, respectively. Identical measured downwind ammonia concentration data were entered into each model. The results of this study indicate that calculated emission rates and/or emission factors are model specific, and no simple conversion factor can be used to adjust emission rates and/or factors between models. Therefore, emission factors developed using one model should not be used in other models to determine downwind pollutant concentrations.

Particulate matter emission factors for almond harvest as a function of harvester speed.

Abstract Almond harvest accounts for substantial particulate matter less than 10 µm in aerodynamic diameter (PM10) emissions in California each harvest season. This paper addresses the reduction of harvester ground speed from a standard 8 km/hr (5 mph) to 4 km/hr (2.5 mph) as a possible mitigation measure for reducing PM10 emissions. Ambient total suspended particulate (TSP) and PM10 sampling was conducted during harvest with alternating control (8 km/hr [5 mph]) and experimental (4 km/hr [2.5 mph]) treatments. On-site meteorological data were used in conjunction with both Industrial Source Complex-Short Term version 3 (ISCST3) and the American Meteorological Society/U.S. Environmental Protection Agency Regulatory Model (AERMOD) dispersion models to back-calculate emission rates from the measured concentrations. Baseline annual emission factors for nut pickup of 381 ± 122 and 361 ± 123 kg PM10/km2·yr were determined using ISCST3 and AERMOD, respectively. Both of these values are substantially lower than the current PM10 emission factor for almond pickup of 4120 kg PM10/km2·yr. The particulate matter less than 2.5 µm in aerodynamic diameter (PM2.5) emission factors for nut pickup developed from this study were 25 ± 8 kg PM2.5/km2·yr and 24 ± 8 kg PM10/km2·yr were determined using ISCST3 and AERMOD, respectively. Reducing harvester speed resulted in an emissions reduction of 42% for TSP, but no differences were detected in emissions of PM10 and PM2.5. Differences detected in the emission factors developed using ISCST3 and AERMOD were not statistically significant, indicating that almond harvest emission factors previously developed using ISCST3 may be applied appropriately in AERMOD.

Evaluation of Modern Cotton Harvest Systems on Irrigated Cotton: Harvester Performance

Picker and stripper harvest systems were evaluated on production-scale irrigated cotton on the High Plains of Texas over three harvest seasons. Observations on harvester performance, including time-in-motion, harvest loss, seed cotton composition, and turnout, were conducted at seven locations with multiple cultivars. In systems where sufficient support equipment was available, strippers had higher productivity (i.e. acres per hour) than pickers. In higher yielding cotton, pickers had a higher productivity rate than strippers. The picker harvest had higher harvest losses but also resulted in lower levels of foreign matter and, therefore, higher turnout. The results of this research have elsewhere been incorporated into an economic model comparing harvest systems under various yield conditions.

Determining Seasonal Greenhouse Gas Emissions from Ground-Level Area Sources in a Dairy Operation in Central Texas

ABSTRACT Greenhouse gas (GHG) emissions from agricultural production operations are recognized as an important air quality issue. A new technique following the U.S. Environmental Protection Agency Method TO-14A was used to measure GHG emissions from ground-level area sources (GLAS) in a free-stall dairy operation in central Texas. The objective of this study was to quantify and report GHG emission rates (ERs) from the dairy during the summer and winter using this protocol. A weeklong sampling was performed during each season. A total of 75 and 66 chromatograms of air samples were acquired from six delineated GLAS (loafing pen, walkway, barn, silage pile, settling basin, and lagoon) of the same dairy during summer and winter, respectively. Three primary GHGs—methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O)—were identified from the dairy operation during the sampling periods. The estimated overall ERs for CH4, CO2, and N2O during the summer for this dairy were 274, 6005, and 7.96 g head−1day−1, respectively. During the winter, the estimated overall CH4, CO2, and N2O ERs were 52, 7471, and 3.59 g head−1day−1, respectively. The overall CH4 and N2O ERs during the summer were approximately 5.3 and 2.2 times higher than those in the winter for the free-stall dairy. These seasonal variations were likely due to fluctuations in ambient temperature, dairy manure loading rates, and manure microbial activity of GLAS. The annualized ERs for CH4, CO2, and N2O for this dairy were estimated to be 181, 6612, and 6.13 g head−1day−1, respectively. Total GHG emissions calculated for this dairy with 500 cows were 2250 t of carbon dioxide equivalent (CO2e) per year. IMPLICATIONS The agricultural sector, especially concentrated animal feeding operations (CAFOs) contribute a considerable amount of GHGs to the atmosphere. To develop abatement strategies to reduce GHG emissions, it is important to learn to collect, analyze, verify, and report real data on actual emissions. Therefore, there is a need for a robust and accurate technique/protocol to measure GHGs from CAFOs. It is important to obtain direct estimates of GHG emissions from different GLAS in CAFOs to compile emission inventories and to develop GLAS-specific abatement strategies.

Evaluation of modern cotton harvest systems on irrigated cotton: fiber quality

Picker and stripper harvest systems were evaluated on production-scale irrigated cotton on the High Plains of Texas over three harvest seasons. Observations on fiber quality using High Volume Instrument (HVI) and Advanced Fiber Information Systems (AFIS) were made on multiple cultivars harvested from six locations. When fibers were relatively immature, micronaire, length, and length uniformity as measured by HVI were better for picker harvested cotton than for stripped cotton leading to a higher loan value and average sale price for the producer. In cases where fibers were more mature, differences in fiber quality parameters between picked and stripped cottons were less pronounced leading to less discrepancy in the value of cotton harvested. However, differences in nep counts, short fiber content, and visible foreign matter between harvest treatments were still distinguishable. The results of this study indicate that producers may realize greater fiber quality and lint value by using picker harvesters, but the magnitude of those differences are a function of growing conditions and/or fiber maturity. Differences in cultivars also played a large role in determining fiber properties.

Evaluation of particulate matter abatement strategies for almond harvest.

ABSTRACT Almond harvest accounts for substantial PM10 (particulate matter [PM] ≤10 μm in nominal aerodynamic diameter) emissions in California each harvest season. This paper evaluates the effects of using reduced-pass sweepers and lower harvester separation fan speeds (930 rpm) on lowering PM emissions from almond harvesting operations. In-canopy measurements of PM concentrations were collected along with PM concentration measurements at the orchard boundary; these were used in conjunction with on-site meteorological data and inverse dispersion modeling to back-calculate emission rates from the measured concentrations. The harvester discharge plume was measured as a function of visible plume opacity during conditioning operations. Reduced-pass sweeping showed the potential for reducing PM emissions, but results were confounded because of differences in orchard maturity and irrigation methods. Fuel consumption and sweeping time per unit area were reduced when comparing a reduced-pass sweeper to a conventional sweeper. Reducing the separation fan speed from 1080 to 930 rpm led to reductions in PM emissions. In general, foreign matter levels within harvested product were nominally affected by separation fan speed in the south (less mature) orchard; however, in samples conditioned using the lower fan speed from the north (more mature) orchard, these levels were unacceptable. IMPLICATIONS The results of this research indicate that PM emissions from almond sweeping operations may be reduced by use of reduced-pass sweepers. Additionally, increased efficiencies in fuel consumption and time required for sweeping may be realized by use of reduced-pass sweepers. Reducing harvester separation fan speeds results in lower emissions from nut conditioning, but foreign matter levels in conditioned samples from more mature orchards were unacceptable.

EFFECTS OF CYCLONE DIAMETER ON PERFORMANCE OF 1D3D CYCLONES : CUTPOINT AND SLOPE

Cyclones are a commonly used air pollution abatement device for separating particulate matter (PM) from air streams in industrial processes. Several mathematical models have been proposed to predict the cutpoint of cyclones as cyclone diameter varies. The objective of this research was to determine the relationship between cyclone diameter, cutpoint, and slope of the fractional efficiency curve (FEC) based on empirical data. Tests were performed comparing cutpoints and FEC slopes of 15.24, 30.48, 60.96, and 91.44 cm (6, 12, 24, and 36 in.) diameter cyclones with poly-disperse PM having an aerodynamic mass median diameter near 10 µm. The mass of PM collected by the cyclones and the mass and particle size distributions of PM that penetrated the cyclones were used to determine each cyclones FEC, characterized by a cutpoint and slope. The cutpoints of cyclones showed no relationship to cyclone diameter, while the slope of the cyclone FECs increased as cyclone diameter increased. Statistically different collection efficiencies were observed among the 30.48, 60.96, and 91.44 cm (12, 24, and 36 in.) diameter cyclones. None of the previously published mathematical models analyzed in this article accurately predicted cyclone cutpoint.

Comparison of seasonal phenol and p-cresol emissions from ground-level area sources in a dairy operation in central Texas

Although there are more than 200 odor-causing volatile organic compounds (VOCs), phenol and p-cresol are two prominent odor-causing VOCs found downwind from concentrated animal feeding operations (CAFOs). The VOC emissions from cattle and dairy production are difficult to quantify accurately because of their low concentrations, spatial variability, and limitations of available instruments. To quantify VOCs, a protocol following U.S. Environmental Protection Agency (EPA) Method TO-14A has been established based on the isolation flux chamber method and a portable gas chromatograph (GC) coupled with a purge-and-trap system. The general objective of this research was to quantify phenol and p-cresol emission rates (ERs) from different ground-level area sources (GLASs) in a free-stall dairy during summer and winter seasons using this protocol. Two-week-long sampling campaigns were conducted in a dairy operation in central Texas. Twenty-nine air samples were collected during winter and 37 samples were collected during summer from six specifically delineated GLASs (barn, loafing pen, lagoon, settling basin, silage pile, and walkway) at the free-stall dairy. Thirteen VOCs were identified during the sampling period and the GC was calibrated for phenol and p-cresol, the primary odorous VOCs identified. The overall calculated ERs for phenol and p-cresol were 2656 ± 728 and 763 ± 212 mg hd−1 day−1, respectively, during winter. Overall phenol and p-cresol ERs were calculated to be 1183 ± 361 and 551 ± 214 mg hd−1 day−1, respectively, during summer. In general, overall phenol and p-cresol ERs during winter were about 2.3 and 1.4 times, respectively, higher than those during summer. Implications: Concentrated animal feeding operations contribute a considerable amount of VOCs to the atmosphere. The phenol and p-cresol are two VOCs recognized as potential odor-causing compounds emitted from livestock operation. To develop effective strategies for mitigating livestock odorous VOC emissions, relative emissions from different GLAS in a livestock operation under different climate conditions should be quantified. It is also important to obtain direct estimates of VOC emissions from different GLAS in CAFOs to compile emission inventories. This research determined phenol and p-cresol emissions from different GLAS in a free-stall dairy and also identified areas in a dairy operations that have the highest phenol and p-cresol emissions.

Influence of Harvesting and Gin Cleaning Practices on Southern High Plains Cotton Quality

Southern High Plains cotton has improved over the last ten years with regard to yield and fiber length and strength. In light of increased adoption of picker harvesting to preserve fiber quality and improve harvest productivity, ginning practices are needed which preserve fiber quality and maximize return to the producer. The objective of this work was to investigate the influence of harvest method, number of seed-cotton extractor cleaners (e.g. stick machines), and seed-cotton cleaning rate on foreign matter content, lint value, and fiber and yarn quality of cotton produced in the Southern High Plains. Compared to using only one stick machine, the use of two stick machines in the seed-cotton cleaning system removed more foreign material from both picker- and stripper-harvested cotton, but more foreign material was removed by the stick machines from stripper-harvested cotton because it had higher initial foreign matter content. Seed-cotton cleaning rate had no influence on stick machine cleaning performance for picked cotton but higher cleaning rates reduced stick machine cleaning performance for stripper-harvested cotton. Picker-harvested cotton exhibited improved HVI and AFIS fiber quality and higher bale values compared to stripper-harvested cotton. The use of two stick machines improved fiber color properties and reduced lint foreign matter content. Seed-cotton cleaning rate had a minimal effect on fiber quality and bale value was not influenced by the number of stick machines or seed-cotton cleaning rate. Total lint value, on a production area basis, was higher for stripper-harvested cotton after both lint cleaners compared to picker-harvested cotton due to yield differences. Yarn imperfections were reduced for ring spun yarn produced from picker-harvested cotton processed through one stick machine at the high cleaning rate. The findings of this work support a recommendation for using one stick machine in seed-cotton cleaning systems processing picker-harvested cotton and two stick machines in systems processing stripper-harvested cotton.