Mitigating odors from animal facilities using biofilters
Mitigating odors from livestock sites using biofilters was addressed in this dissertation which is organized in paper format and comprises a literature review paper and two original research papers. In the first literature review paper, both the laboratory and field research from 1997 to 2008 was reviewed to give an up-to-date perspective of studies on the mitigation of odors and volatile organic compounds (VOCs) relating to agricultural facilities using biofilters. A mobile biofiter testing system was developed which can be used at field conditions to evaluate biofilter performance at variable media types, empty bed residence times (EBRT) and media moisture contents. A field study for mitigating odors and odorous compounds from a deep-pit swine finishing facility in central Iowa was conducted to test two types of wood chip media (western cedar and two inch hardwood) using the mobile biofilter testing system. The biofilter testing system was continuously operated and evaluated at different media moisture content levels and different air flow rates resulting in a variable EBRT from 1.6 to 7.3 sec. A dynamic forced-choice olfactometer was used to evaluate odor concentrations from both the control plenum and biofilter treatments. Hydrogen sulfide and ammonia concentrations were also measured from these olfactometry samples. Solid-phase microextraction fibers were used to extract VOCs from both the control plenum and biofilter treatments. Analyses of VOCs and its corresponding individual odors were carried out using a gas chromatography-mass spectrometry-olfactometry (GC-MS-O) system. Pressure drop characteristics through the biofilters packed with western cedar and hardwood media were monitored. The reduction efficiency and pressure drop characteristics obtained with the wood chip-based biofilters indicate the feasibility of farm-level applications of wood chip-based biofilters for reducing swine building odors. The results also showed that both a proper media moisture content and a minimum EBRT were critical to a successful wood chip-based biofilter.