In Canada, the piggery industry is an essential part of the agricultural sector, but the anaerobic storage conditions of swine slurry lead to the emission of methane (CH4), an important greenhouse gas. This study examined the influence of the CH4 concentration and the nitrate-nitrogen concentration in the nutrient solution on the performance of a biofilter packed with an inorganic material treating low concentrations of CH4, between 0.16 and 2.8 g m(-3), representative of the piggery industry. A maximum elimination capacity of 14.5 +/- 0.6 g m(-3) h(-1) was obtained for an inlet load of 38 1 g m(-3) h(-1). The biofilter satisfied first order kinetics with a value of 7.5 h(-1) for the first order constant. Nitrate concentrations from 0 to 0.5 gN L-1 were tested at an inlet load of 14 g m(-3) h(-1) and a nitrate concentration of 0.1 gN L-1 was sufficient for proper biofilter operation. When no inorganic nitrogen was provided in the nutrient solution. the removal efficiency remained at 18 +/- 0.7% suggesting the presence of methanotrophs capable of fixing atmospheric nitrogen. Carbon and nitrogen mass balances suggested that the carbon accumulated within the biofilter was probably used for the production of exopolymeric substances or intracellular compounds. (C) 2011 Elsevier B.V. All rights reserved.