Biofiltration refers to the removal and oxidation of organic gases (i.e., volatile organic compounds, or VOCs) from contaminated air by vapor phase biodegradation in beds (biofilters) of compost, soil, or other materials such as municipal waste, sand, bark peat, volcanic ash, or diatomaceous earth. As contaminated air (such as air from a soil vapor extraction process) flows through the biofilter, the VOCs sorb onto surfaces of the pile and are degraded by microorganisms. Nutrient blends or exogenous microbial cultures can be added to a biofilter to enhance its performance. Moisture needs to be continually supplied to the biofilter to counteract the drying effects of the gas stream. The stationary support media that make up the biofiltration bed should be porous enough to allow gas flow through the biofilter and should provide a large surface area with high wetting and sorptive capacities. This support media should also provide...