Simulation of gas concentration during the process of air injection and extraction in a landfill

Old landfills require pre-aeration before excavation to reduce the emissions of volatile organic compounds and methane. Variation and distribution of gas species during landfill aeration is important in designing an aeration system and evaluating aeration progress. Limited research is conducted on the variation of gas concentration in aerobic landfills considering methane oxidation and aerobic waste degradation. In this study, a numerical model is developed considering reactions to simulate the changes in methane, oxygen, and carbon dioxide concentrations in landfills during air injection and extraction. Parameter sensitivity analyses are conducted to evaluate the effects of permeability, dispersion coefficient, maximum methane oxidation rate, and oxygen consumption rate on simulation results. Results show that the model is sensitive to oxygen consumption rate. Overall, the application of this model in aerobic landfills provides a practical method to predict gas concentration variation. This model can be used in the optimal design of in situ aeration system.