A linear inclination with PCO2 was presented in Fig. 5. The tendency of operating line having a slope of 0.0329 C per unit of PCO2 was observed. An average DT of 2.86 C was obtained at average carbon dioxide production of 79.97 g m3 h1. Comparatively slightly higher elevation in packed bed temperature was found during second set of experiments. In the previous study (Ramirez et al., 2008), it was reported that the ratios of temperature/ carbon dioxide production rate (PCO2 ) were 0.024 C and 0.15 C per unit ofPCO2 for biofiltration and biotrickling filter, respectively.