ReSource International has developed a world-leading method of quantifying and mapping landfill gas emissions using UAVs (drones), which has been demonstrated in recent tests to be accurate compared to controlled releases.
A highly accurate (±0.6ppb) methane sensor is flown on a UAV downwind of the landfill site. Windspeed measurements are taken on the UAV and on the ground, and the result of this can be used to give a precise flux rate after the plume is reconstructed by a software algorithm.
This method, based on pilot work conducted in Sweden (in press) compares well to acetylene tracer methods in both controlled release and real-world situations down to flow rates of just a few kg/h. It appears to be significantly more precise than traditional flux-box measurements, which require unrealistically high sampling densities for precise measurements.
To map emissions sources, the UAV is flown at low altitude (typically 15m if a local topographic model is available) and emissions are algorithmically interpolated to give a map of emissions sources. Sources typically are a short distance upwind of where the UAV first measures the plume. The same gas sensor can be easily dismounted from the UAV and used to trace gas leaks to cm-level precision using a handheld wand. Approximately 200 ha per day could be covered using this approach, depending on density.
UAVs flying at 35km/h can be used to quickly and safely build a near-ground map of emissions that would otherwise be laborious, dangerous or impossible. Precision is also greatly improved over ground-based mapping of complex sites, as wind direction is more likely to be constant and “pools” of gas are ignored.
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