|Parnell, Jr, Calvin|
Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 7/1/2002
Publication Date: 7/1/2002
Citation: Buser, M.D., Parnell, Jr, C.B., Shaw, B.W., Lacey, R.E. 2002. Characterization of dusts emitted by cotton gins in terms of true pm10. National Cotton Council Beltwide Cotton Conference. CD ROM. Interpretive Summary: Agricultural operations are encountering difficulties complying with the current air pollution regulations for particulate matter (PM). The regulations are based on the National Ambient Air Quality Standards (NAAQS), which set maximum limits for ambient PM based on protecting public health. PM is currently regulated in terms of particle diameters less than or equal to a nominal 10 microns (PM10). Compliance with the PM regulations may be determined through dispersion modeling. Modeling requires emission rates, which are determined from EPA's list of emission factors or from source sampling. Emission factors are industry specific. PM10 emission factors are typically determined from source sampling based on EPA's Method 201a sampling protocol. Ultimately, this method would produce an accurate measure of PM less than or equal to 10 microns. However, this method uses a cyclone to separate the smaller particles from the larger particles and the cyclones are not perfect and errors are introduced due to the interaction of the particle size and cyclone performance characteristics. Two theoretical methods were introduced to estimate the true PM10 emitted from the ten process streams associated with a standard cotton gin. These estimates show that cotton gins are being forced to comply with more stringent PM regulations than urban type sources. The bottom line is that regulatory agencies are using sampling methods developed to regulate urban sources to regulate agricultural sources, and these methods introduce substantial errors when the methods or samplers are exposed to larger dusts than they were designed to sample.
Technical Abstract: Agricultural operations across the United States are encountering difficulties in complying with the current air pollution regulations for particulate matter (PM). Cotton gins are most frequently regulated based on results obtained from dispersion modeling that utilize emission factors from EPA's 1996 AP-42 or emission factors derived from source sampling. PM10 emission factors are typically determined from source sampling based on EPA's Method 201a sampling protocol. EPA has documented the performance characteristics of the cyclones used in Method 201a, which are similar to the performance characteristics of an ambient PM10 sampler. Recent research has shown that ambient PM10 samplers can over-estimate the true PM10 in the ambient air when the sampler is exposed to dust with a mass median diameter larger than 10 microns. The purpose of this manuscript is to explore the potential impacts associated with determining PM10 emission values for cotton gin exhausts using the EPA's Method 201a. Two theoretical methods were introduced to estimate the true PM10 emitted from the ten process streams associated with a standard cotton gin. Estimates from the first and second methods showed that the true PM10 was about 38 and 63% lower than that obtained by PM10 source sampling. For the theoretical methods (method 1 and 2) used in this paper, the estimates of the true percent PM10 was 28 and 24%, respectively. Whereas the current estimate is 39%, as defined in EPA's 1996 AP-42. Therefore, when cotton gins are regulated based on PM10 emission factors from AP-42 or emission factors derived from source sampling based on EPA's Method 201a, they are being forced to comply with more stringent PM regulations than urban type sources.