Development of Cotton Gin PM2.5 Emission Factors for EPA’s AP-42

Abstract. The Compilation of Air Pollution Emission Factors (AP-42) emission factors are assigned ratings, from A (Excellent) to E (Poor), based on the quality of data used to develop them. AP-42 currently contains no PM2.5 cotton gin emission factors. In an effort to develop science-based data for regulating the industry, a national cotton gin particulate matter emissions study was conducted from 2008 to 2011, in which PM2.5 emission factors were developed for individual processing systems from seven cotton gins across the U.S. This paper used data from the gin stack sampling study and EPA guidelines to develop proposed PM2.5 emission factors for 17 cotton gin systems for EPA’s AP-42. Two methods of calculating the emission factors were compared. These methods were compared to each other and the National Study technical reports. The method that used average gin ITRs and test values (ITR Design 1) was determined to be the best for calculating emission factors as it has a built-in mechanism for screening outliers and reasonably prevents a single facility from biasing an emission factor. Using ITR Design 1, eight of the 17 emission factors rated as “poorly representative,” and the other nine rated as “moderately representative.”