A New Technique for Airborne Measurements to Quantify Methane Emissions Over a Wide Range: Implementation and Validation

• Main Authors: Dooley, Jonathan F., Minschwaner, Kenneth, Dubey, Manvendra K., Abbadi, Sahar H., Sherwin, Evan D., Meyer, Aaron G., Follansbee, Emily, Lee, James E.
• Format: Text
• Language: English
• Published: 2024
• Subjects: permafrost
• Online Access: https://doi.org/10.5194/egusphere-2024-760; https://egusphere.copernicus.org/preprints/2024/egusphere-2024-760/

Methane (CH 4 ) is a powerful greenhouse gas with a global warming potential 84 times higher than carbon dioxide (CO 2 ) over 20 years. CH 4 is produced from many natural and anthropogenic sources which can be further classified as biogenic or thermogenic in origin. The largest biogenic sources result from anaerobic decay such as wetlands, melting permafrost, or the breakdown of organic matter in the guts of ruminant animals. Thermogenic CH 4 is generated during the breakdown of organic matter at high temperatures and pressure within the Earth's crust, a process which also produces more complex trace hydrocarbons such as ethane (C 2 H 6 ) and propane (C 3 H 8 ). Emissions of thermogenic CH 4 are dominated by the fossil fuel energy sector, and the presence of elevated C 2 H 6 along with CH 4 can be used to distinguish oil and gas emissions from biogenic sources. This work outlines the development and deployment of an Unmanned Aerial System (UAS) outfitted with a fast (1 Hz) and sensitive (1–2 ppb s -1 ) CH 4 & C 2 H 6 sensor and ultrasonic anemometer. The UAV platform is a vertical-takeoff, hexarotor vehicle capable of vertical profiling to 120 m altitude and plume sampling across scales up to 1 km. This system has been used for direct quantification of point sources, as well as distributed emitters such as landfills, with source rates as low as 0.04 kg h -1 and up to 1500 kg h -1 . Simultaneous measurements of CH 4 and C 2 H 6 mixing ratios, vector winds, and positional data allows for source classification (biogenic versus thermogenic), differentiation, and emission rates without the need for modeling or a priori assumptions about winds, vertical mixing, or other environmental conditions. The UAS has been deployed throughout the Southwest United States for system validation and targeted quantification of various sources emitting at or below the detection limits of other aircraft and satellite systems. This system offers a direct, repeatable method of horizontal and vertical profiling of ...