An innovative biofiltration technology based on anoxic biodegradation was proposed in this work for the treatment of inert VOC-laden emissions from the petrochemical industry. Anoxic biofiltration does not require conventional O-2 supply to mineralize VOCs, which increases process safety and allows for the reuse of the residual gas for inertization purposes in plant. The potential of this technology was evaluated in a biotrickling filter using toluene as a model VOC at loads of 3, 5, 12 and 34 g m(-3) h(-1) (corresponding to empty bed residence times of 16, 8, 4 and 1.3 min) with a maximum elimination capacity of similar to 3 g m(-3) h(-1). However, significant differences in the nature and number of metabolites accumulated at each toluene load tested were observed, o- and p-cresol being detected only at 34 g m-3 h-1, while benzyl alcohol, benzaldehyde and phenol were detected at lower loads. A complete toluene removal was maintained after increasing the inlet toluene concentration from 0.5 to 1 gm(-3) (which entailed a loading rate increase from 3 to 6 g m-3 h-1), indicating that the system was limited by mass transfer rather than by biological activity. A high bacterial diversity was observed, the predominant phyla being Actinobacteria and Proteobacteria. (C) 2013 Elsevier B.V. All rights reserved.