A finite-volume numerical model for temporal and spatial variability of methane oxidation in landfill covers

• Published in: Computers and geotechnics Vol. 122; p. 103510
• Main Authors: Feng, Shi-Jin, Bai, Zhen-Bai, Zheng, Qi-Teng, Lu, Shi-Feng, Zhang, Xiao-Lei
• Format: Journal Article
• Language: English
• Published: New York Elsevier Ltd 01.06.2020; Elsevier BV
• Subjects: Capacity; Diffusion effects; Diffusion rate; Efficiency; Field tests; Finite volume method; Gas flow; Gaseous diffusion; Heat transfer; Landfill; Landfill covers; Landfill gas; Landfills; Mathematical models; Methane; Methane oxidation; Moisture content; Multiphase flow; Numerical models; Oxidation; Oxidation rate; Preferential flow; Soil; Spatial distribution; Spatial variations; Temporal and spatial variability; Temporal variations; Two phase flow; Variability; Waste disposal sites; Water content; Finite volume method; Methane oxidation; Landfill covers; Temporal and spatial variability
• ISSN: 0266-352X; 1873-7633
• DOI: 10.1016/j.compgeo.2020.103510

A multi-field model is proposed to study methane oxidation in landfill covers, especially its temporal and spatial variability. The proposed model consists of water-gas two-phase flow, multi-component gas flow, heat transfer, and biochemical reaction modules, and is solved using OpenFOAM based on the finite volume method. Applying this model, the coupled effect of gas diffusion, temperature and oxidation rate is studied, and the influence of water content on oxidation efficiency and capacity is quantified. The temporal variability of oxidation efficiency and capacity in landfill covers is illustrated by modelling a long-term field test. It is found that the CH4 removal rate can reach 40 g d−1 m−2 in the summers and drop to less than 10 g d−1 m−2 in the winters. A 3-D landfill cover cell with a cracked zone is applied to illustrate the spatial variability of oxidation, and a significant preferential flow can be observed when the cracked zone depth of a 1 m thick soil cover exceeds 0.8 m. The above studies demonstrate that the proposed model is able to predict temporal and spatial distributions of methane oxidation efficiency and capacity, and some results contribute to a better understanding of methane oxidation in landfill covers.