Short communication Biofiltration of methane from ruminants gas effluent using Autoclaved Aerated Concrete as the carrier material Giovanni Ganendra a,d , Daniel Mercado-Garcia a , Emma Hernandez-Sanabria a , Nico Peiren b , Sam De Campeneere b , Adrian Ho c , Nico Boon a,⇑ a Laboratory of Microbial Ecology and Technology, Ghent University, Coupure Links 653, B-9000 Gent, Belgium b Institute for Agriculture and Fisheries Research, Animal Sciences Unit, Scheldeweg 68, Melle 9090, Belgium c Department of Microbial Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Droevendaalsesteeg 10, 6708 PB Wageningen, The Netherlands d SIM vzw, Technologiepark 935, BE-9052 Zwijnaarde, Belgium highlights  A biofilter was utilized to remove methane from ruminants gas effluent.  Autoclaved Aerated Concrete was used as the biofilter carrier material.  The average removal efficiency in the biofilter was 17.5%.  Complete carbon sequestration from the removed methane was achieved. article info Article history: Received 29 January 2015 Received in revised form 16 April 2015 Accepted 24 April 2015 Available online 1 May 2015 Keywords: Livestock methane emission mitigation Methane biofilter Methane-Oxidizing Bacteria Autoclaved Aerated Concrete Carbon sequestration abstract The performance of Methane-Oxidizing Bacteria (MOB) immobilized on Autoclaved Aerated Concrete (AAC) in a biofilter setup to remove methane from ruminants gas effluent was investigated. Two dairy cows were housed in respiration chambers for two days where the exhaust gas from the chambers was used as the biofilter feed. MOB consumed methane at an average removal efficiency (RE) of 17.5% and elimination capacity of 67.3 g m 3 d 1 . Several factors that might cause this low RE were the: (a) low methane inlet concentration (average concentration = 61.9 ppmv), (b) presence of ammonia in the inlet gas (average concentration = 1.54 ppmv), (c) the high gas feed flow rate (1.2 m 3 h 1 ), and (d) the lowering humidity level in the biofilter (average RE = 15.9%). By using AAC as the carrier material, carbon dioxide was removed in the biofilter by the likely carbonation reaction with AAC (average RE = 4.02%). Thus, complete carbon sequestration from the converted methane was obtained. Overall, our results showed that an environmentally friendly methane biofilter process could be achieved when using ACC as the carrier material. Ó 2015 Elsevier B.V. All rights reserved. 1. Introduction Methane emitted from livestock contributes up to 40% of the global anthropogenic methane emission [1]. Effective livestock methane emission mitigation strategies should focus on emission originating from the ruminants as it accounts for 90% of the total livestock methane emission [2]. Current approaches include the addition of feed supplements to reduce methane generation from rumen, management practices to improve meat/milk efficiency, and genetic selection [2–4]. However, methane is constantly produced in the rumen and retained in the effluent gas. Ruminants produce methane as a result of the microbial diges- tion of the food in the rumen and large intestines [5]. Protein, starch, and other polysaccharides are hydrolyzed and fermented partly to hydrogen and acetic acid. These components are subse- quently converted to methane by methanogens. Methane repre- sents energy loss from the fermentation process and it is primarily emitted by eructation [6]. Methane can also be emitted by flatulation or methanogenesis in the anaerobic part of manure, although they do not constitute a significant part of the total rumi- nant methane emission. Carbon dioxide is produced from both res- piration and eructation, while ammonia and nitrous oxide are http://dx.doi.org/10.1016/j.cej.2015.04.128 1385-8947/Ó 2015 Elsevier B.V. All rights reserved. ⇑ Corresponding author at: Ghent University, Faculty of Bioscience Engineering, Laboratory of Microbial Ecology and Technology (LabMET), Coupure Links 653, B-9000 Gent, Belgium. Tel.: +32 (0)9 264 59 76; fax: +32 (0)9 264 62 48. E-mail address: Nico.Boon@UGent.be (N. Boon). URL: http://www.labmet.Ugent.be (N. Boon). Chemical Engineering Journal 277 (2015) 318–323 Contents lists available at ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej