[Abstract] This study has compared the efficiency of 3 mixes of organic materials [peat + coco fibre; branches (1 vol) + wood (1vol) + peat (1 vol.); + branches (5 vol) + wood (2vol) + peat (1 vol.)] used in biofiltres pilot plants in order to remove Volatiles Organic Compounds (VOCs), Ammonia and Odours Units (O.U.) from process and ambient air of a composting plant. After a period of seeding, 3 different air velocities have been applied (125 m/h, 175 m/h and 200 m/h) during approximately 1 ½ month each. Results show a better NH3 removal in filters containing wood (92% to 98%) than in the one with coco fibre (between 17% and 63%) depending on the air velocity and on the pollutant concentration (from 35 to 60 ppmV). Concerning VOCs the efficiency was globally the same (approx. 75%) and that for each velocity and for a relatively constant inlet concentration of 20 ppmV Carbon equivalent. Differences are less obvious in terms of Odours Unit that is mainly due to the variability of the analysis itself. The coco fibres filter seems to be a little bit worst than the two others what would be in accordance with the pollutant removal efficiency observed
