Research Paper Field evaluation of biofilters in reducing aerial pollutant emissions from a commercial pig finishing building Teng-Teeh Lim a, *, Yaomin Jin b , Ji-Qin Ni b , Albert J. Heber b a Food Systems and Bioengineering, University of Missouri, 230 Agricultural Engineering Building, University of Missouri, Columbia, MO 65211-5200, USA b Agricultural & Biological Engineering, Purdue University, 225 S. University Street, West Lafayette, IN 47907-2093, USA article info Article history: Received 29 June 2011 Received in revised form 27 February 2012 Accepted 1 April 2012 Published online 4 May 2012 Two elevated-bed, wood-chip biofilters were tested at a commercial pig finishing farm in Indiana for effectiveness in mitigating aerial pollutant emissions. Three wooden sampling chambers were installed to contain and redirect two biofilter-treated and one untreated exhaust streams. Two trials were conducted to test the effects of biofilter thickness, which included 127-mm and 254-mm of media depths. The two biofilters with 127-mm media thickness reduced concentrations of ammonia (NH 3 ) by 31.2% ( p < 0.05) and 18.1% ( p > 0.05), and hydrogen sulfide (H 2 S) by 26.6% ( p < 0.05) and 23.6% ( p < 0.05) in the pit fan exhaust air, respectively. Insignificant reductions of methane concentrations were observed. The biofilters with 254-mm media thickness significantly ( p < 0.05) reduced concentrations of NH 3 by 45.8% and 18.0%, and H 2 S by 42.2% and 27.9%, respectively. Significant reductions ( p < 0.05) of particulate matter (PM 10 ), and total suspended particulate were 62.0% and 89.7% for the 127-mm biofilters, and 62.9% and 96.3%, for the 254-mm biofilters, respectively. Very low inlet PM 2.5 concentrations were detected. Average pressure drops of the biofilters ranged from 29.6 to 57.2 Pa. The empty bed residence times (EBRTs) were 0.3 s and 0.6 s for the 127-mm and 254-mm biofilters, respectively. Frequent maintenance checks to minimise compaction and ensure uniform moisture content were required to ensure minimal pressure drops and maximal aerial pollutant removal effi- ciency. The biofilters were relatively simple and inexpensive to install. Although the EBRT was relatively short, the biofilters exhibited low to medium mitigation effectiveness. Higher mitigations would be obtained using biofilters with greater media volumes corre- sponding to longer EBRTs. ª 2012 IAgrE. Published by Elsevier Ltd. All rights reserved. 1. Introduction The livestock industry has traditionally been an important sector of the U.S. economy. However, increased public concerns regarding aerial pollutant emissions and potentially more stringent environmental regulations are some of the immediate challenges faced by the industry. Cost-effective methods are being sought to alleviate odour and other envi- ronmental impacts of pollutant emissions. Several abatement studies have been conducted to reduce odour emissions: diet * Corresponding author. Tel.: þ1 573 882 9519; fax: þ1 573 884 5650. E-mail addresses: limt@missouri.edu (T.-T. Lim), biofiltration@gmail.com (Y. Jin), jiqin@purdue.edu (J.-Q. Ni), heber@purdue.edu (A.J. Heber). Available online at www.sciencedirect.com journal homepage: www.elsevier.com/locate/issn/15375110 biosystems engineering 112 (2012) 192 e201 1537-5110/$ e see front matter ª 2012 IAgrE. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.biosystemseng.2012.04.001