This research focuses on the performance study of a full-scale biofilter for treating a stream of vent gas with airborne VOCs generated from a chemical plant wastewater treatment facility. The biofilter consists of two parallel 20-ft standard containers in each a space of 5.98 m in length, 2.35 m in width and 0.50 m in height were filled with biofiltering media prepared by blending swine-manure compost and fern chips in a certain proportion. The vent gas contains methane, methanol, ethanol, acetone, dichloromethane, methyl ethyl ketone, ethyl acetate and toluene as major components and has an average flow rate of 1,320 m3/h (22 m3/min) and a temperature of 16-40oC. The purposes of this research were to confirm the VOC removal efficiency and to evaluate the elimination capacity for each VOC by monitoring operating parameters, including gas flow rate, system temperature, influent and effluent VOC concentrations of the biofilter. Experimental results show the system has a volumetric influent gas flow rate 1,153-1,470 m3/h which resulted in an average gas empty bed retention time (EBRT) of 0.64 min through the bed, a moisture of 25-70% and a pH of 2.4-6.9 for the media. Removal efficiencies of methane, methanol, ethanol, acetone, dichloromethane, MEK, ethyl acetate, toluene, NMHC and THC were 23.1, 79.3, 95.2, 82.9, 53.5, 63.7, 83.9, 41.2, 76.2 and 50.5%, respectively. Results also indicate that the VOC removal efficiency for each compound was not directly related to such important operating parameters of the biofilter as influent gas flow rate, media temperature, media pH, and the VOC concentration of the influent gas. However, the volumetric elimination rate (K) was approximately linearly varied with the corresponding loading (L) for the biodegradable VOCs in the influent gas. An average removal efficiency (K/L) of 24.5% was obtained with loadings of L < 70 g/m3h for methane. K/L of 91 and 54% were obtained for methanol with L = 0-7 and 15-22 g/m3h, respectively. Average K/L of 95% was obtained for both ethanol and acetone with L < 40 g/m3h. Removal efficiencies of 48 and 76% were obtained for methanol with L = 0-10 and 18-35 g/m3h, respectively. For MEK, an average removal of 89% was obtained with L = 0.5-4 g/m3h. Removal efficiencies of 84, 37, 48, 76 and 51% were obtained with L < 20, 0-0.2, 0.3-0.8 <60 and <120 g/m3h for ethyl acetate, toluene, NMHC and THC, respectively. This full-scale biofilter is effective in removing ethanol, ethyl acetate, acetone, methanol, and MEK. There is no significant removal efficiency for dichloromethane, toluene and methane. The performance can hopefully be improved by controlling the media in suitable conditions of moisture 50-60% and pH 7-8.