Biof iitration is an established economical air pollution control technology for removing organic contaminants in air. Existing filters using natural media, such as peat and compost, were demonstrated in the field for degrading up to several thousand ppm of contaminants. An engineered biofilter using synthetic media, such as activated carbon, has been developed that shows improvements in removal efficiency, biodegradation and space requirements over the existing filters. This carbon filter has been operated for >11 months in a bench-top unit, accomplishing ≥90 percent removal efficiency consistently in a stream containing 10 to 20 ppm of toluene. The mass transfer zone remained stationary and extremely short (1 to 4 seconds of empty bed contact time) during the entire operating period. Compared with existing filters, this engineered filter showed 40 to 80 times greater biodegradation efficiency under the selected conditions, resulting in a decreased space requirement and other advantages in equipment sizing. In addition, the engineered filter allows for removal of biomass, with no medium compaction and no replacement or excess disposal of spent media required. The unit, kept in a humid state supplemented with inorganic nutrients, offers a desirable environment for biogrowth. The extremely efficient bio-regeneration shown in this study indicates that the biofilter could also replace some existing carbon applications, particularly for removal of weakly-adsorbed, but biodegradable, contaminants or applications with strong competition by moisture.