alpha-Pinene biodegradation was evaluated in mesophilic and thermophilic biotrickling filters. The potential of silicone oil for enhancing the removal was evaluated too, at both temperatures. Performance was studied at empty bed residence times between 60 and 14 s, and concentrations of 0.06-38.84 g m(-3), with or without silicone oil. Efficiency decreased as the pollutant concentration was increased, showing higher elimination capacities at higher EBRTs. In the absence of silicone oil, better results were obtained in the thermophilic than in the mesophilic bioreactor. At similar loads (360 g m(-3) h(-1)), in the thermophilic bioreactor the elimination capacity was 293 g m(-3) h(-1), with a removal efficiency of 81%, while in the mesophilic BTF the elimination capacity only reached 195 g m(-3) h(-1), for that same load. The presence of a second liquid phase improved performance of both bioreactors. With 5% silicone oil, elimination capacities as high as 2000 g m(-3) h(-1) were achieved, under either mesophilic or thermophilic conditions. (C) 2010 Elsevier Ltd. All rights reserved.