Biological treatment using methane-oxidizing bacteria (MOB) immobilized on six porous carrier materials have been used to mitigate methane emission. Experiments were performed with different MOB inoculated in building materials at high (similar to 20 % (v/v)) and low (similar to 100 ppmv) methane mixing ratios. Methylocystis parvus in autoclaved aerated concrete (AAC) exhibited the highest methane removal rate at high (28.5 +/- 3.8 mu g CH4 g(-1) building material h(-1)) and low (1.7 +/- 0.4 mu g CH4 g(-1) building material h(-1)) methane mixing ratio. Due to the higher volume of pores with diameter > 5 mu m compared to other materials tested, AAC was able to adsorb more bacteria which might explain for the higher methane removal observed. The total methane and carbon dioxide-carbon in the headspace was decreased for 65.2 +/- 10.9 % when M. parvus in Ytong was incubated for 100 h. This study showed that immobilized MOB on building materials could be used to remove methane from the air and also act as carbon sink.