Thermal imaging and fugitive CH4 emissions at Tenerife’s municipal solid waste landfill

Fugitive methane (CH₄) emissions from municipal solid waste landfills represent a significant and often underestimated source of greenhouse gases, particularly in complex sites with multiple cells at different operational stages. In this study, diffuse carbon dioxide (CO₂) and CH₄ emissions were investigated at the Tenerife municipal solid waste landfill (Canary Islands, Spain), combining ground-based flux measurements with thermal infrared imaging acquired by unmanned aerial vehicles (UAVs). 

Diffuse gas fluxes were measured using the accumulation chamber method across more than 1,700 sampling points distributed over active, sealed and closed landfill cells. CH₄ emissions were quantified both directly, using an in situ CH₄ sensor, and indirectly, by estimating CH₄ fluxes from measured CO₂ fluxes and CH₄/CO₂ concentration ratios in the chamber headspace. In parallel, UAV-based thermal surveys were conducted to explore surface temperature patterns and their potential relationship with diffuse gas emissions and landfill cover characteristics. 

Results show clear spatial variability in diffuse gas emissions linked to the operational status of the cells. Active and recently used cells exhibit higher and more spatially heterogeneous CH₄ fluxes, while sealed and older cells are characterized by lower direct CH₄ emissions but relatively higher indirect CH₄ estimates. This discrepancy is attributed to CH₄ oxidation and limited surface permeability, which reduce effective CH₄ transfer to the atmosphere while allowing CO₂ to diffuse more efficiently. 

The combined use of direct and indirect flux measurements together with thermal imaging provides complementary insights into landfill gas dynamics, allowing differentiation between effective atmospheric emissions and subsurface CH₄ presence. This integrated approach improves the characterization of fugitive emissions and supports the assessment of landfill gas management efficiency.