Update on the Development of Cotton Gin PM2.5 Emission Factors for Epa's AP-42

A cotton ginning industry-supported project was initiated in 2008 to update the U.S. Environmental Protection Agency’s (EPA) Compilation of Air Pollution Emission Factors (AP-42) to include PM_2.5 emission factors. This study develops emission factors from the PM_2.5 emission factor data collected from the industry supported project (hereafter referred to as “National Study”) for 17 cotton gin systems and rates their quality using EPA’s new Emission Factor Development Procedures (published August 2013). Stack emissions were collected using Method 201a with a PM₁₀ and PM_2.5 cyclone and Method 17 in combination with particle size analysis. Unrepresentative test runs were removed from the National Study dataset if gin operation was erratic, laboratory errors occurred, or if indicated to be an outlier by either of two outlier tests. The remaining test runs were assessed for quality using the EPA’s Test Quality Rating Tool and assigned Individual Test Ratings (ITRs).The test runs and ITRs were averaged for each method used at a gin. The averages were used to develop emission factors and their representativeness ratings. This resulted in eight “poorly” and nine “moderately” representative emission factors, and a range of 0.002 (mote trash) to 0.032 lbs. of PM_2.5 per bale (unloading). While no factors received a rating of “highly representative,” having PM_2.5 emission factors developed from sampled data, as opposed to being estimated from PM₁₀ factors, will provide science based data for regulating the industry.