Atmospheric methane removal by methane-oxidizing bacteria immobilized on porous building materials

Abstract

Biological treatment using Methane Oxidizing Bacteria (MOB) immobilized on carrier materials is considered as the best solution to mitigate methane emission at low concentrations (e.g., in animal houses). The porosity of the support is one of the most important factors for an efficient removal of methane. In animal houses, building materials having a high porosity may provide a niche for MOB. In this study, we evaluated the methane removal capacity of MOB immobilized on porous building materials. Six different types of building materials and MOB were chosen for the experiments. Building materials were immersed in an MOB liquid culture (2.108 cells/ml) and after 24 hours the liquid were separated. The methane removal capacity of MOB was investigated by analyizing the evolution of the methane concentration in the headspace of a closed incubator containing the materials at starting concentrations of ~20 %(v/v) and ~50 ppmv. MOB immobilized on Maastricht limestone and Ytong exhibited higher methane removal rates compared to when immobilized in other materials with M. parvus NCIMB 11129T in Maastricht limestone (0.1 mg CH4 (m3air h)-1) exhibited the highest rate at ~50 ppmv and M. trichosporium NCIMB 11131T in Maastricht limestone (1451 mg CH4 (m3air h)-1) at ~20 %(v/v). Both materials exhibited the highest macropores (i.e., pore diameter > 3 ?m) volume. Therefore, they were likely to accommodate more bacteria and consequently higher methane removal rate by the MOB. M. parvus and M. trichosporium were able to remove methane for two months with decreasing activity. From this study it was shown that methane can be efficiently removed from the air by MOB immobilized on building materials.