Second stage seed-cotton cleaning system particulate emission factors for cotton gins: Particle size distribution characteristics

Authors: BOYKIN, JAMES - Retired ARS Employee; BUSER, MICHAEL - Oklahoma State University; Whitelock, Derek; Holt, Gregory

Submitted to: Journal of Cotton Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/29/2015
Publication Date: 11/12/2015
Publication URL: http://handle.nal.usda.gov/10113/61751
Citation: Boykin, J.C., Buser, M.D., Whitelock, D.P., Holt, G.A. 2015. Second stage seed-cotton cleaning system particulate emission factors for cotton gins: Particle size distribution characteristics. Journal of Cotton Science. 19:401-414.

Interpretive Summary: In 2006, the U.S. Environmental Protection Agency (EPA) implemented a more stringent air quality standard for very fine dust smaller than 2.5 micrometers in diameter (PM2.5). Also, quality ratings for EPA emission factors for cotton gin particulate with a diameter less than or equal to 10 micrometers (PM10) are extremely low. The primary issue affecting the cotton industry across the country is that cotton gins may not be regulated fairly, because very little scientifically sound information is available on cotton gin emissions. Since all cotton gins will eventually be impacted by these issues, cotton ginners’ associations across the cotton belt agreed that there was an urgent need to collect cotton gin emissions data to address the PM2.5 standards and current regulatory issues concerning PM10 emission factors. The EPA-approved methodology to measure emissions utilizes size selective particulate samplers. There is a body of evidence that raises questions regarding the effectiveness of these samplers and points to a critical need for additional information about the particulate sampled. In response, seven cotton gins at locations across the cotton belt were sampled by the USDA-ARS Cotton Ginning Laboratories and Oklahoma State University to develop particle size characteristics for the dust emitted while processing cotton. Using these characteristics, it was found that the second stage seed-cotton cleaning systems at the gins sampled emitted on average 0.0031 pounds of PM2.5 for every 500 pound bale of cotton produced and 0.056 pounds of PM10 per bale. These results were lower than those measured utilizing EPA-approved methods. This information will go further to ensure that cotton gins are appropriately permitted and accounted for in state and federal regulations. Also, this may allow many gins to avoid installing additional dust control measures with substantially higher capital and operating costs that will impact the ginning cost to the farmer.

Technical Abstract: This report is part of a project to characterize cotton gin emissions from the standpoint of total particulate stack sampling and particle size analyses. In 2013, Environmental Protection Agency (EPA) published a more stringent standard for particulate matter with nominal diameter less than or equal to 2.5 µm (PM2.5). This created an urgent need to collect additional cotton gin emissions data to address current regulatory issues, because EPA AP-42 cotton gin PM2.5 emission factors did not exist. In addition, current EPA AP-42 emission factor quality ratings for cotton gin PM10 (particulate matter with nominal diameter less than or equal to 10 µm) data are questionable and extremely low. The objective of this study was to characterize particulate emissions for second stage seed-cotton cleaning systems from cotton gins located in regions across the cotton belt based on EPA-approved total particulate stack sampling methodologies and particle size analyses. Average measured PM2.5, PM10 and PM10-2.5 emission factors based on the mass and particle size analyses of EPA Method 17 total particulate filter and wash samples from five gins (14 total test runs) were 0.0014 kg/227-kg bale (0.0031 lb/500-lb bale), 0.025 kg/bale (0.056 lb/bale), and 0.024 kg/bale (0.052 lb/bale), respectively. The second stage seed-cotton cleaning system particle size distributions were characterized by an average mass median diameter of 12.21 µm (aerodynamic equivalent diameter) and a geometric standard deviation of 3.11. Based on system average emission factors, the ratio of PM2.5 to total particulate was 2.4%, PM2.5 to PM10 was 5.6%, PM10 to total was 43%, and PM10-2.5 to total was 41%. Particle size distribution based system average PM2.5 and PM10 emission factors were 39% and 64% of those measured for this project utilizing EPA-approved methods. The particle sized distribution based PM10 emission factor was 60% of that currently published in EPA AP-42 for the No. 2 dryer and cleaner system.