Biofiltration of Simulated Air Pollutants from Distillers Dried Grains with Solubles (DDGS) Dryer Vents at Corn-Derived Ethanol Production Facilities Li-Jung Chen, a Katherine M. Bangs, a Kerry A. Kinney, a Lynn E. Katz, a and A. Frank Seibert b a Department of Civil, Architectural and Environmental Engineering, ECJ 8.6, University of Texas at Austin, Austin, TX 78712; kakinney@mail.utexas.edu (for correspondence) b Separations Research Program, University of Texas at Austin, Austin, TX 78712 Published online 3 September 2009 in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ep.10401 The DDGS dryer vents at corn-derived ethanol pro- duction facilities often contain a mixture of odorous and/or potentially hazardous air pollutants including acetaldehyde and formaldehyde. The objective of this study was to investigate the feasibility of utilizing a biofilter system to treat the volatile organic com- pounds (VOCs) released from the DDGS dryer stack during ethanol production. Single aldehyde elimina- tion capacity experiments indicate that both acetalde- hyde and formaldehyde are readily biodegraded in a biofilter at a short contact time of 10 s, although the acetaldehyde removals during the initial start up pe- riod were lower than those observed during later operation. A biofilter packed with porous silicate pel- lets at neutral pH successfully achieved greater than 90% removal of VOC mixtures containing acetalde- hyde, formaldehyde, ethanol, and acetic acid. How- ever, extended operation with the four component VOC mixture led to a decline in biofilter pH. At low pH (4.6), acetaldehyde removal declined from 95 to 62% and ethanol removal declined from 90 to 57%. The option of utilizing a water scrubber upstream of the biofilter to remove acetic acid was investigated; it was determined that effective acetic acid removal was possible in a recirculating water scrubber main- tained at a pH level above 7, where the rate of re- moval was controlled by gas phase mass transfer re- sistance. Ó 2009 American Institute of Chemical Engineers Environ Prog, 29: 116–126, 2010 Keywords: acetaldehyde, formaldehyde, biofilter, hazardous air pollutant, ethanol, acetic acid INTRODUCTION Development of alternative renewable energy sources has accelerated rapidly over the past few years as we seek to ease our dependence on expen- sive fossil fuels and to meet our growing energy demands. In the United States, the Energy Independ- ence and Security Act of 2007 requires that U.S. energy providers produce at least 36 billion gallons of biofuel by 2022 [1]. Ethanol is widely viewed as an environmentally friendly alternative to fossil fuels as well as a replacement for methyl tertiary butyl ether, a gasoline oxygenate that has leaked from under- ground fuel storage tanks and contaminated ground- water aquifers across the United States [2, 3]. The domestic production of ethanol from corn stocks has soared recently from 2 billion gallons in 2002 to 9 bil- Ó 2009 American Institute of Chemical Engineers 116 April 2010 Environmental Progress & Sustainable Energy (Vol.29, No.1) DOI 10.1002/ep