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<p>Methane oxidation biosystems (MOBs) are an effective approach for mitigating fugitive landfill methane (CH₄) emissions, but moisture accumulation near the downslope gas distribution layer (GDL)-methane oxidation layer (MOL) interface can restrict CH₄ entry and concentrate CH₄ migration upslope. Existing analyses have inferred gas occlusion in MOBs from predicted volumetric water content (VWC) at the GDL-MOL interface without explicitly simulating gas redistribution through the MOB. This study used a process-based numerical model that resolves coupled water flow, gas transport, heat transfer, and microbial CH₄ oxidation in MOBs. A dual-porosity hydraulic formulation was incorporated to better represent gravel-amended compost MOLs, and the updated model was validated against CH₄ flux, VWC, and temperature data from a field-scale sloped MOB constructed in Ontario, Canada. Results showed that downslope partial occlusion restricted CH₄ entry locally, but lateral redistribution within the MOL reduced this non-uniformity before CH₄ reached the surface. This finding demonstrates that water-only analyses can overestimate the persistence of gas restriction originating at the GDL-MOL interface and its effect on CH₄ flux distribution. A MOL composition analysis evaluated how gravel amendment of compost altered capillary barrier behaviour, moisture accumulation near the GDL-MOL interface, and gas redistribution. Compost-only MOLs developed near-full saturation at the GDL-MOL interface and produced strongly non-uniform surface CH₄ fluxes, whereas gravel-amended compost MOLs weakened the capillary barrier and preserved more uniform gas distributions. These results show that gravel amendment, previously recommended in literature to improve MOL physical structure, also provides a hydraulic and gas-transport benefit by mitigating downslope gas occlusion.</p>

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Capillary Barrier Effects on Gas Transport in Methane Oxidation Biosystems (MOBs): A Process-Based Numerical Modelling Approach

  • 期刊论文

  • 发表日期：

    2026年8月1日

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  • Wameed Alghazali,
  • Cole J.C. Van De Ven

摘要

Methane oxidation biosystems (MOBs) are an effective approach for mitigating fugitive landfill methane (CH₄) emissions, but moisture accumulation near the downslope gas distribution layer (GDL)-methane oxidation layer (MOL) interface can restrict CH₄ entry and concentrate CH₄ migration upslope. Existing analyses have inferred gas occlusion in MOBs from predicted volumetric water content (VWC) at the GDL-MOL interface without explicitly simulating gas redistribution through the MOB. This study used a process-based numerical model that resolves coupled water flow, gas transport, heat transfer, and microbial CH₄ oxidation in MOBs. A dual-porosity hydraulic formulation was incorporated to better represent gravel-amended compost MOLs, and the updated model was validated against CH₄ flux, VWC, and temperature data from a field-scale sloped MOB constructed in Ontario, Canada. Results showed that downslope partial occlusion restricted CH₄ entry locally, but lateral redistribution within the MOL reduced this non-uniformity before CH₄ reached the surface. This finding demonstrates that water-only analyses can overestimate the persistence of gas restriction originating at the GDL-MOL interface and its effect on CH₄ flux distribution. A MOL composition analysis evaluated how gravel amendment of compost altered capillary barrier behaviour, moisture accumulation near the GDL-MOL interface, and gas redistribution. Compost-only MOLs developed near-full saturation at the GDL-MOL interface and produced strongly non-uniform surface CH₄ fluxes, whereas gravel-amended compost MOLs weakened the capillary barrier and preserved more uniform gas distributions. These results show that gravel amendment, previously recommended in literature to improve MOL physical structure, also provides a hydraulic and gas-transport benefit by mitigating downslope gas occlusion.