Modeling of Methane Migration and Oxidation in Biochar-amended Landfill Cover Soil

The global warming potential (GWP) of methane (CH4) is 25 times the GWP of carbon dioxide (CO2); as such, controlling CH4 emissions at municipal solid waste (MSW) landfills is an urgent task. Oxidation of CH4 using soil covers and bio-enhanced covers as a CH4 mitigation strategy is receiving great attention from environmental professionals. Biochar-amended soil covers are proposed to effectively oxidize CH4. Biochars are able to adsorb CH4 and improve CH4 oxidation by providing a stable environment for methanotrophic bacteria, making them attractive alternatives to other biocover substrates used in landfill sites. In this study, biochar produced from wood pellets by pyrolysis at 520°C is proposed for use. Several series of batch and column experiments were conducted to investigate CH4 adsorption kinetics and isotherms and CH4 oxidation. A model based on mass balance and previous study was developed to simulate the column experiments, which can well express the process of CH4 migration, adsorption, oxidation, temporary storage and emission in the system. Experimental conditions such as temperature, moisture content and flow rate were taken into consideration. After calibration and verification of the model, there is an excellent agreement with measured and predicted CH4 concentrations in different depths of column, as well as in the outflow. The model established can be used to explain the mechanism of CH4 removal in biochar-amended landfill soil and provide some guidance for field studies and implementation.