Biofiltration consists of a filter-bed of organic matter serving both as carrier for the active biomass and as nutrient Supply, through which the polluted gas passes. The selection of a suitable medium material is of major importance to ensure optimum biofilter efficiency. Peanut shells are an agricultural byproduct locally available in large quantities at a low price in most tropical and sub-tropical countries. A previous study showed that peanut shells are physically and chemically suitable for biofiltration. This paper presents the results obtained during a six month biofiltration experiment using peanut shells as medium and methanol as air pollutant. It is shown that peanut shells are potentially suitable as biofiltration medium, since degradation rates of up to 30 kg MeOH/m(3) d with an empty bed residence time of 19s was obtained. The biofilter showed a good resistance to shock load and no operational problems were observed. (C) 2009 Elsevier Ltd. All rights reserved.