Compost-based biofilters are one of the most cost effective treatment technologies for low concentration air pollutants, compared to traditional technologies such as thermal and catalytic oxidation. Recent cost analysis performed for the petroleum and agricultural industries indicates that biobased systems are more economical than conventional technology. In the biofilter, air pollutants are collected and passed through a reactor containing a packing (e.g., compost) seeded with a microbial biofilm (composted material is pre-inoculated with a diverse microbial community capable of degraded a wide range of air pollutants). In addition to compost, other amendments (e.g., wood chips) are added to reduce pressure drop and/or a solid phase buffer. As the emissions pass through the biofilter, the air pollutants are transported from the gas phase to the stationary water/biofilm on the compost matrix and degraded to CO2 and H2O by the microorganisms in the biofilm. If the air pollutants are inorganic in nature (e.g., NH3), lithotrophic bacteria present in the compost will consume the inorganic compound as an energy source (e.g., nitrifying bacteria that convert NH3 + O2 + H+ ? NH4NO3 salts, equation not balanced).