Cotton Gin Yard and Road Dust Emissions and the Resulting Effects on Downwind Samplers

The control of particulate matter emissions from cotton gins is a priority in many states. The air pollution regulatory process requires that concentrations measured off-property be less than the National Ambient Air Quality Standards. Two methods are commonly used to determine the concentrations on or beyond the property line: ambient sampling and dispersion modeling. In order to limit the emissions from a cotton gin, the State Air Pollution Regulatory Agencies require that the gin obtain a permit. This permit sets the Allowable Emission Rate for the primary criteria pollutant of concern, particulate matter with an aerodynamic equivalent diameter of ten microns or less. The Environmental Protection Agency (EPA) has established emission factors for the particulate emissions from cotton gins in its AP-42 document. When using dispersion modeling or measuring ambient mass concentrations downwind of a cotton gin to determine if it is meeting its allowable emission rate, it is important to note that there are two sources of particulate matter. The exhaust systems from the machinery used to extract the cotton and bale is the source that is being permitted. The gin yard and roads also produce particulate matter. However, these sources are considered to be fugitive emissions, and are not regulated unless the source is considered to be a major source under the Title V operating permit program. There are no cotton gins that currently meet the threshold to be considered a Title V major source, so these emissions should not be regulated. It was hypothesized by the authors that the gin yard and road emissions can contribute significantly to the downwind concentrations. This was demonstrated using the EPA-approved Gaussian-based model, Industrial Source Complex Short Term Version 3 (ISCST3). With this dispersion model, it was possible to distinguish between sources and the concentrations resulting from those sources. The emissions from the gin yard and roads were estimated using AP-42 emission factors, and applied using two processes that are described in detail in the methods section. The average contribution of the gin yard and road uncontrolled emissions was found to be as high as 35% based upon the processes and model assumptions. While this contribution is not precisely what is found on an actual gin yard, it does demonstrate the necessity of including the gin yard and road emissions when determining the concentrations off-property. Introduction The control of dust emissions from cotton gins is a priority in many states. The air pollution regulatory process requires that the concentrations off-property be less than the National Ambient Air Quality Standards (NAAQS). Two methods have been used to determine concentrations of regulated pollutants on or beyond the property line: (1) measurements using ambient samplers and (2) modeling. In order to limit emissions from cotton gins, State Air Pollution Regulatory Agencies (SAPRA) require them to acquire permits. The SAPRA air permit defines the air pollution abatement system and the associated Allowable Emission Rates (AER). The primary pollutant emitted by cotton gins is Particulate Matter (PM) with an Aerodynamic Equivalent Diameter (AED) of 10 micrometers AED (PM10). EPA has published emission factors for emissions of total suspended particulate (TSP) and PM10 from cotton gins in a document referred to as AP-42 (USEPA, 1995). There are several permitting programs that potentially affect agricultural operations in the United States. These programs are used to enforce emission limits based upon NAAQS. The AER is often dependent upon whether the operation is located in an attainment area or not. An attainment area is defined by the EPA as an area considered to have air quality as good as or better than the national ambient air quality standards as defined in the Clean Air Act. (USEPA, 1997) These permits include the New Source Review (NSR) and Title V operating permits. The NSR Permits include: the Prevention of Significant Deterioration (PSD) permit, non-attainment NSR permits, and minor 2005 Beltwide Cotton Conferences, New Orleans, Louisiana January 4 7, 2005 602