Chemical Engineering Journal 168 (2011) 151–158 Contents lists available at ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej Biofiltration of methane at low concentrations representative of the piggery industry—Influence of the methane and nitrogen concentrations Matthieu Girard a , Antonio Avalos Ramirez a , Gerardo Buelna b , Michèle Heitz a,∗ a Department of Chemical Engineering and Biotechnological Engineering, Faculty of Engineering, Université de Sherbrooke, 2500 Boulevard de l’Université, Sherbrooke, Québec, Canada, J1K 2R1 b Centre de Recherche Industrielle du Québec, 333 rue Franquet, Québec, Canada, G1P 4C7 article info Article history: Received 7 July 2010 Received in revised form 15 December 2010 Accepted 15 December 2010 Keywords: Biofiltration Methane Piggery industry Greenhouse gases Nitrogen Inorganic filter bed abstract 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 (CH 4 ), an important greenhouse gas. This study examined the influence of the CH 4 concentration and the nitrate-nitrogen concentration in the nutrient solution on the performance of a biofilter packed with an inorganic material treating low concentra- tions of CH 4 , 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 ± 1gm -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 suf- ficient 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 fix- ing 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. © 2011 Elsevier B.V. All rights reserved. 1. Introduction In Canada, the piggery industry is an essential part of the agri- cultural sector, comprising more than 64,000 direct and indirect jobs [1]. In 2009 alone, there were over 28 million hogs produced in Canada with exports worth just under 3 billion dollars [2]. How- ever, the main waste product of this industry, swine slurry, causes severe environmental problems. The anaerobic storage conditions of this waste product lead to the emission of methane (CH 4 ), an important greenhouse gas (GHG). In fact, in Canada in 2008, swine slurry management was responsible for the release of 1.3 million metric tons of carbon dioxide (CO 2 ) equivalent of CH 4 [3]. In terms of climate change, CH 4 has a global warming potential 25 times that of CO 2 for a 100-year time horizon [4]. Methane is produced by the anaerobic digestion of organic matter by microorganisms which occurs mainly during the stor- age of swine slurry. Typical concentrations of CH 4 in the polluted air from pig houses vary between 0.005 and 0.1 g m -3 (7 and 150 ppmv) and depend essentially on the ventilation flow rate. Methane concentrations ([CH 4 ]) from covered slurry storages with ∗ Corresponding author. Tel.: +1 819 821 8000x62827; fax: +1 819 821 7955. E-mail address: Michele.Heitz@USherbrooke.ca (M. Heitz). no aeration can reach 425 g m -3 (65%, v/v), but storage covers are rarely airtight and concentrations usually vary from 0.1 to 20 g m -3 (150–30,600 ppmv) [5]. In order to limit the piggery industry’s impact on climate change, GHG emissions must be reduced or treated. Methane emissions can be reduced by modifying the hogs’ diet, treating the slurry or decreasing the slurry’s biological activity [6–8]. To mitigate CH 4 emissions, it is possible to collect the gas and burn it using a flare, but concentrations are rarely high enough for direct combustion which requires a minimal concentration of 130 g m -3 (20%, v/v) [9]. An innovative approach uses microorganisms to oxidize CH 4 into CO 2 , water, salts and biomass. This process can be carried out in a biofilter where the polluted gas passes through a bed packed with a porous humid material on which microorganisms capa- ble of degrading the specific contaminants are established [10,11]. This phenomenon has been studied in the piggery industry with both natural and artificial slurry surface crusts. These surface crusts showed potential for CH 4 removal, but it is difficult to control and optimize the biological reactions [12,13]. Several studies have been carried out on the biofiltration of CH 4 originating from sanitary landfills; Nikiema et al. [14] conducted an extensive review on this topic. Most of these studies used organic packing materials, but promising results have been obtained with inorganic materials [15,16]. For relatively high [CH 4 ]s, between 1385-8947/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.cej.2010.12.054