A field experiment was conducted using a full-scale ceramic biofilter (approximately 150 m3/min) in order to determine the potential for biofiltration to remove malodorous gases from composting facilities. The main compounds found in malodorous gases were NH3 and H2S. These compounds were analyzed by a UV-spectrophotometer and gas chromatograph. The microbial carrier was a porous ceramic consisting of diatomite and fly ash. About 12 m3 of ceramic media inoculated with waste activated sludge were filled in the biofilter. The experimental conditions were space velocity of 500 hr(-1), empty bed residence time of 7.2 s, and linear velocity of 0.2 m/s. About 90 L/d of water were sprayed for the operation. The NH3 concentration in inlet gases ranged from 8 to 90 ppmv. The concentration of H2S ranged from 3.2-5.5 ppmv. The acclimation of the biofilter was slow, but more than 95% of removal efficiency was achieved after one month of operation. No nutrients were supplied to the biofilter. The pressure drop in the biofilter varied from 20-40 mmAq during the operation. The energy consumption of this biofilter was about 200 kW/d. It was estimated that the deodorization using this ceramic biofilter was successfully carried out to remove the odor emitted from composting facilities.