The objective behind this study is to select a suitable inorganic packing material for methane biofiltration. Three packing materials are to be compared: two rock materials (average particles' sizes: 2 and 5？mm) and one porous clay particles (average particle size of 7？mm). The main parameter used to assess the efficiency of the packing material is the methane elimination capacity. The study reveals that the rock material having an average particle size around 2？mm is to be preferred. This result is probably due to its high specific surface area and to its good surface properties as compared to the other 2 tested porous materials. The influence of the nonirrigation with the nutrient solution of the biofilter is also investigated. It has been found that nonirrigation of biofilter causes the biofilter performance to decrease significantly (e.g., 45% decrease in 1 week) even with the humidification of the gas phase prior to its introduction into the biofilter. 1. Introduction Methane (CH4) is the most important greenhouse gas (GHG) after carbon dioxide (CO2). Its worldwide contribution to the greenhouse effect is estimated to 15% while for CO2, it is 78%. Methane has a global warming potential of 21, when compared to CO2, for a lifespan in the atmosphere of around 12 years [1]. Methane emissions are encountered in agriculture, in the energy sector, and in landfills with the latter being responsible for 25% of the total CH4 emissions in Canada. It is to be noted that around 60% of the total worldwide emissions of CH4 are of anthropogenic sources [2]. To avoid direct emissions into the atmosphere of the deleterious CH4, biofiltration can be used. This bioprocess involves microorganisms that biodegrade the target pollutant. The interest given to biofiltration is due to its operational cost, generally considered as lower than other elimination techniques such as the flaring. For a successful operation of a biofilter, a solid phase, also called packing material, on which the microorganisms attach and then grow, is required. Nonoptimized selection of the packing material generally yields an inefficient biological process [3] while its optimization results in lower footprint requirements. Packing materials that may be used during CH4 biofiltration are grouped into 2 main categories: organic and inorganic materials. Organic materials include composts and soils and are generally considered by several authors as the preferred materials [4]. The main advantages of those materials are that they are easily accessible and can naturally contain methanotrophic bacteria,
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