Response of compost biocover to freeze-thaw cycles: Column experiments Farzad Moghbel, Mamadou Fall ⁎ Department of Civil Engineering, University of Ottawa, 161 Colonel by, Ottawa K1N 6N5, Ontario, Canada abstract article info Article history: Received 22 December 2014 Received in revised form 11 August 2016 Accepted 2 September 2016 Available online 4 September 2016 The microbial oxidation of methane in biocover is considered a promising technology for the mitigation of meth- ane emissions from landfills. In the present paper, the behaviour (evolution of methane and oxygen concentra- tion, volumetric water content and temperature) and performance under freeze-thaw cycles (FTCs) conditions are investigated by column experiments. In the utilizing of column experiments, three columns are developed, manufactured, prepared and treated by a period of methane injection (0 FTC), after 1 FTC and 2 FTCs, in three re- spective stages. One column is instrumented with various sensors to monitor the evolution of temperature, vol- umetric water content, settlement and gas composition at four different depths for one of the biocover columns. In addition, laboratory testing is carried out on the biocover samples with regards to their organic content and grain size distribution. The results show that two FTCs have effect on the methane removal of compost biocover as well as influence the evolution of the volumetric water content, temperature, settlement, gas composition and organic content of the biocover. However, these effects and influence are more significant in the upper layers (≤ 15 cm) of the compost biocover column. The results presented in this paper will contribute to a better design of landfill biocovers in cold regions. © 2016 Elsevier B.V. All rights reserved. Keywords: Biocover Compost Climate change Freeze-thaw Cold regions Methane 1. Introduction Amongst the greenhouse gases (GHGs), methane (CH 4 ) has been the subject of exclusive research as the 100-year global warming potential for CH 4 is around 28 times greater than that of CO 2 (IPCC, 2014). One of the major CH 4 production sources is by waste sector landfills (Bogner et al., 2007). Recent studies show that CH 4 gas production from the waste industries are considered as the second highest source of anthropogenic CH 4 emission in Europe (Scheutz et al., 2003, 2009) and the third highest source in the US (EPA, 2014). Landfills produce 21% and 30% of all anthropogenic CH 4 emissions in Canada and Europe, respectively (Perdikea et al., 2008). Moreover, in developing countries that are experiencing economic and population growth, the quantity of CH 4 generated from landfills is increasing (Khoshand and Fall, 2014). Landfill gas collection systems are mandatory in many countries in order to prevent or decrease the amount of landfill gas (LFG) emissions into the atmosphere (Ait-Benichou et al., 2009). However, these sys- tems are not economically efficient in landfills that are small in size, old in age or located in cold regions (Zeiss, 2006), where the rate of LFG emissions is not sufficient for utilizing burning or energy recovery systems (Huber-Humer et al., 2009). Moreover, as uncontrolled dumps or landfills with (temporary) inactive gas collection systems are also potential sources of LFG (Ait-Benichou et al., 2009), both fugi- tive and residual emissions may exist during the life time of a landfill (Roncato and Cabral, 2012). A green and novel solution for preventing or limiting landfill meth- ane escape is the utilization of biocovers. Biocovers are a type of landfill top cover which enhances the environmental circumstances for methanotroph bacteria which consume (i.e. oxidize) CH 4 during its es- cape from landfills (Huber-Humer et al., 2009). Several studies have demonstrated biocovers to be a promising technology for mitigating CH 4 emission from landfills (e.g. Roncato and Cabral, 2012; Chi et al., 2012; Zeiss, 2006). Moreover, previous investigations (e.g., Humer and Lechner, 1999; Huber-Humer, 2004; Wilshusen et al., 2004) have re- ported that stabilized compost materials are a suitable biocover medi- um for CH 4 oxidation. However, many aspects of the practical application of compost as landfill biocovers in cold regions have not been investigated and/or are not understood. One of these aspects is the response of biocovers to freeze-thaw cycles (FTCs). Cold and freeze-thaw climatic conditions are common in many countries or regions in the world. In such locali- ties, particularly those with long and cold winters, biocovers remain covered under snow or frozen for a long period of time (Rykaart and Hockley, 2009). They will be also subjected to freeze-thaw cycles. FTCs may alter the performance of the biocover. For instance, FTCs may Cold Regions Science and Technology 131 (2016) 39–45 ⁎ Corresponding author. E-mail address: mfall@uottawa.ca (M. Fall). http://dx.doi.org/10.1016/j.coldregions.2016.09.005 0165-232X/© 2016 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Cold Regions Science and Technology journal homepage: www.elsevier.com/locate/coldregions