Applications of Ground-Based Hyperspectral Imaging for Methane Detection in Landfills

Abstract Description: Anthropogenic emissions of methane, a greenhouse gas 28 times more potent than carbon dioxide at trapping heat from the atmosphere (over 100 years), must be reduced rapidly to avoid the worst outcomes of climate change. Within North America, landfills represent approximately 20% of anthropogenic landfill emissions and are currently being targeted by existing and proposed legislation in multiple jurisdictions. Current approaches for measuring landfill emissions mainly rely on localized point concentration measurements. Still, the effectiveness of these strategies is limited due to the diffuse, nonuniform, and intermittent nature of the emissions (e.g., “hot spots”) and the complex interactions between the wind and the vegetated surface. Moreover, conducting the extensive surveys needed to obtain reliable estimates is highly costly and time-consuming. 

The current study examines the potential of long-wave hyperspectral imaging operating between 7.43 and 13.30 μm to investigate methane concentrations from landfills. The hyperspectral camera generates a three-dimensional data cube, where each pixel in the 14°x11° field-of-view contains an additional spectral dimension. By applying the radiative transfer equation and the absorption characteristics of the gases between the camera and the background, the column densities of the gases, air temperature, and background temperature can be inferred through inverse analysis. Methane column density measurements are validated on a pixel-wise basis using an open-path tunable diode laser absorption spectrometer system (Boreal GasFinder3 OP) operating at the 1653 nm methane line. The results show that the ground-based hyperspectral camera is capable of detecting methane hot spots with sufficient temperature difference between the background and the ambient air.