The authors are solely responsible for the content of this technical presentation. The technical presentation does not necessarily reflect the official position of the American Society of Agricultural and Biological Engineers (ASABE), and its printing and distribution does not constitute an endorsement of views which may be expressed. Technical presentations are not subject to the formal peer review process by ASABE editorial committees; therefore, they are not to be presented as refereed publications. Citation of this work should state that it is from an ASABE meeting paper. EXAMPLE: Author's Last Name, Initials. 2012. Title of Presentation. ASABE Paper No. 12----. St. Joseph, Mich.: ASABE. For information about securing permission to reprint or reproduce a technical presentation, please contact ASABE at rutter@asabe.org or 269-932-7004 (2950 Niles Road, St. Joseph, MI 49085-9659 USA). An ASABE Meeting Presentation Paper Number: 12-1338423 A Feasible Biofilter Media Moisture Sensor Liangcheng Yang, ASABE Member Engineer Department of Agricultural and Biological Engineering, University of Illinois at Urbana- Champaign. Email: yang126@illinois.edu Xinlei Wang, ASABE Member Engineer, Associate Professor Department of Agricultural and Biological Engineering, University of Illinois at Urbana- Champaign. Email: xwang2@illinois.edu Ted L. Funk, ASABE Member Engineer, Extension Specialist Department of Agricultural and Biological Engineering, University of Illinois at Urbana- Champaign. Email: funkt@illinois.edu Sijie Shi, Master Student Department of Agricultural and Biological Engineering, University of Illinois at Urbana- Champaign. Email: sshi5@illinois.edu Richard S. Gates, ASABE Fellow, Professor Department of Agricultural and Biological Engineering, University of Illinois at Urbana- Champaign. Email: rsgates@illinois.edu Yuanhui Zhang, ASABE Fellow, Professor Department of Agricultural and Biological Engineering, University of Illinois at Urbana- Champaign. Email: yzhang1@illinois.edu Written for presentation at the 2012 ASABE Annual International Meeting Sponsored by ASABE Hilton Anatole Dallas, Texas July 29 – August 1, 2012 Abstract. Biofiltration is commonly used for the treatment of gases containing low concentrations of ammonia. One very important biofilter operational parameter is the media moisture. High media moisture content usually favors ammonia removal, but leads to production of nitrous oxide - a powerful greenhouse gas. Monitoring and controlling moisture is a technical challenge, since the