Sensitive Drone Mapping of Methane Emissions without the Need for Supplementary Ground-Based Measurements

Abstract

Methane (CH 4 ) is one of the main greenhouse gas for which sources and sinks are poorly constrained and better capacity of mapping landscape emissions are broadly requested. A key challenge has been comprehensive, accurate, and sensitive emission measurements covering large areas at a resolution that allows separation of different types of local sources. We present a sensitive drone-based system for mapping CH 4 hotspots, finding leaks from gas systems, and calculating total CH 4 fluxes from anthropogenic environments such as wastewater treatment plants, landfills, energy production, biogas plants, and agriculture. All measurements are made on-board the drone, with no requirements for additional ground-based instruments. Horizontal flight patterns are used to map and find emission sources over large areas and vertical flight patterns for total CH 4 fluxes using mass balance calculations. The small drone system (6.7 kg including batteries, sensors, loggers, and weather proofing) maps CH 4 concentrations and wind speeds at 1 Hz with a precision of 0.84 ppb/s and 0.1 m/s, respectively. As a demonstration of the system and the mass balance method for a CH 4 source that is difficult to assess with traditional methods, we have quantified fluxes from a sludge deposit at a wastewater treatment plant. Combining data from three 10 min flights, emission hotspots could be mapped and a total flux of 178.4 ± 8.1 kg CH 4 d –1 was determined.

Landfill Emissions of Methane Inferred from Unmanned Aerial Vehicle and Mobile Ground Measurements

“…This is within the lower and upper uncertainty bounds of 17% and 227% estimated by Shah et al [27] for their drone flux measurements. Galfalk et al [29] also used drones to perform multiple methane flux plane measurements surrounding a sludge pile at a wastewater treatment plant with higher resolution wind measurements than in this study. Their reported uncertainties were around 6%, suggesting that spatial and temporal variability are larger sources of emissions uncertainty than measurement error.…”

Identifying CO2 Seeps in a Long-Dormant Volcanic Area Using Uncrewed Aerial Vehicle-Based Infrared Thermometry: A Qualitative Study

“…The use of drones combined with lightweight thermal cameras and/or miniaturized devices for the measurements of concentrations of different gas species has proven to be a powerful tool in the study of volcanic and geothermal areas [ 6 , 46 , 47 ].…”

Critical method needs in measuring greenhouse gas fluxes

“…The rapid general development of Internet of things, automation, and artificial intelligence, is generating synergies and provides communication infrastructure for GHG sensor networks. The combination of vertical perimeter line measurements and mass balance approaches (box S2) are facilitated by recent mobile techniques to map GHG content in upwind and downwind air columns [60,61]. This could become a very suitable approach to rapidly assess fluxes from many types of target areas based on straightforward and consistent principles and calculations, although some challenges regarding consideration of wind speed profiles and dispersion, and their interaction with GHG concentration profiles, remains.…”