Abstract. This study introduces a helicopter-borne mass balance approach, utilizing the HELiPOD platform, to accurately quantify methane (CH4) emissions from coal mining activities. Compared to conventional research aircraft, the use of an external sling load configuration eliminates the need for aeronautical certifications, facilitates easier modifications and enables local helicopter companies to conduct flights. Furthermore, it allows for plume probing as close as several hundred meters downwind of an emission source and offers comprehensive vertical coverage from 50 m to 3 km altitude, making the HELiPOD an ideal tool to distinguish, capture, and quantify emissions from single sources in complex emission landscapes worldwide. Our approach serves as an independent emission verification tool, bridging the gap between ground-based, drone, near-field and far-field airborne measurements and supports identification of CH4 emission mitigation opportunities. Nineteen mission flights were conducted in the Upper Silesian Coal Basin of Southern Poland in June and October 2022 that targeted CH4 emissions from multiple coal mine ventilation shafts and several drainage stations. The comparison of top-down HELiPOD mass flux estimates against those calculated from bottom-up in-mine CH4 safety sensor and air flow measurements revealed very good agreement with relative deviations of 0 % to 25 %. This indicates, notwithstanding associated uncertainties, that the two independent approaches are capable of estimating CH4 emissions from coal mine ventilation shafts accurately. However, the accuracy and representativeness of derived in-mine data is application-specific and should be evaluated by independent measurements. With measured CH4 emission rates up to 3000 kg h−1 from individual coal mine ventilation shafts we confirm prior research, while revealing that emission strengths from drainage stations can be of comparable magnitude and should be investigated further. The possibility to detect emissions at rates as low as 20 kg h−1 with the HELiPOD was demonstrated through a controlled release experiment. This emphasises the wide range of potential applications in quantifying sources within a wide range of CH4 emission rates, i.e. from relatively small sources, e.g. biodigesters, landfills, cattle feedlots and manure pits to larger industrial sources including those from the coal, oil and gas sectors.
Förster et al. (Tue,) studied this question.
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