Physical characterization and quantification of water vapor uptake capacity of landfill biocover media

Recent research in the field of global climate change has listed methane emissions from the landfills as a potent contributor to the global warming. Biologically active cover (biocover) materials are proposed to mitigate the fugitive methane emissions from landfills sites by microbial oxidization of methane to carbon dioxide. In this study, organic clay rich soil and woodchips are proposed as the biocover materials. The efficiency of the methane oxidation has been found to be a function of the biocover material's moisture content (MC). The main objective of this study was to quantify the amount of water vapor uptake by the biocover materials when these materials are in contact with a gas stream at different relative humidities (RHs). Bench scale column tests were conducted to determine the water vapor adsorption capacity of organic clay soil and woodchips obtained from the McCommas Bluff Landfill (MCB-LF) site in the City of Dallas, Texas. Water vapor adsorption breakthrough curves were obtained by humidifying a dry air stream at RH ranging from 75% to 95% and passing it through biocover media column. The MC of the MCB-LF biocover soil increased from 8.9 % to 14 % at 95% RH, adsorbing 38.7 mg water/g MCB-LF soil. The MCB-LF biocover woodchips adsorbed 24.9 mg water/g MCB-LF woodchips when the air stream was at 95% RH, increasing the MC from 10.3 % to 14.4 %. When the MCB-LF biocover soil and woodchips were mixed in volumetric ratios of 1:1, 1:3 and 3:1, respectively, the highest water vapor uptake was exhibited by volumetric ratio of 1:3, where the MC of the biocover media increased from 11.8 % to 12.5 % adsorbing 15.4 mg water/g MCB-LF media. The information obtained from this study was used to design a system that maintained the biocover material at a constant MC of 14% for in-column methane degradation landfill biocover experiments. This research gave a better insight about the moisture sustaining capacity of the MCB-LF organic clay soil and woodchips that would be used as a landfill biocover media for the McCommas Bluff Landfill site to control emissions of methane to the atmosphere.