Figure1: The helicopter sonde HELiPOD and the DLR/TUBS teams in the hangar at the Bielsko-Biala airport, Poland (Foto: DLR / H. Huntrieser, CC BY-ND-NC 3.0).
Within the framework of UNEP´s International Methane Emissions Observatory (IMEO), scientists from the DLR Institute of Atmospheric Physics (DLR-IPA) have just finished successful measurements of methane (CH4) emissions from coal mining operations in Poland. A novel airborne measurement concept for the reliable quantification of greenhouse gas emissions has been developed in close collaboration with the Institute of Flight Guidance (IFF) of the Technische Universität Braunschweig (TUBS). The HELiPOD, a helicopter sonde flown as a sling load in a wire below the helicopter, has been equipped with in situ instrumentation from DLR-IPA to measure important greenhouse gases as CH4 and carbon dioxide (CO2) in vicinity of coal mines. The Upper Silesian Coal Basin (USCB) in Poland, one of the regions in Europe with the highest density of active coal mines where considerable amounts of CH4 are emitted, was selected as target region for the airborne mission.
The airborne measurements were carried out from the airport in Bielsko-Biala and performed in the vicinity of coal mine ventilations shafts, where accumulated CH4 from the underground mines is released in order to prevent explosions. Methane emissions from three different ventilation shafts in the USCB region were probed during 10 mission flights (~30 flight hours) in cooperation with the Polish helicopter company Helipoland. Measurements were performed up- and downwind of the shafts (horizontal distance ~0.5 km - 5 km), and at multiple heights up to ~1-2 km to map the CH4 emissions. During the flights, the HELiPOD mission monitor in the cockpit displayed measurements online allowing the mission scientist to successfully guide the helicopter through the emissions of interest. Combined with highly-resolved wind information from the HELiPOD these measurements will be used to estimate the CH4 flux from the shafts with the ultimate goal to compare these emission rates to reported values from the coal mine operators. Thereby, the variability of CH4 emissions depending on the diurnal work activity in the mines will also be considered. In addition, the airborne measurements were supported by ground-based CH4 measurements carried out by a local team of Polish scientists from the AGH University of Science and Technology in Krakow.
This new measurement strategy using helicopter in-situ measurements to capture CH4 emissions from single point sources was shown to be extremely powerful to study trace gas emissions on local scales. It offers a number of advantages compared to common airborne measurement methods (e.g. reduced flight costs, large manoeuvrability, option to remain at a certain point of interest or to reduce air speed significantly). After the successful demonstration of this novel airborne concept, further joint DLR-TUBS measurements are planned in Poland in October 2022 and in Oman in 2023, funded by UNEP within the IMEO program. In Oman the major goal is to address the lack of methane measurement data from the oil and gas sector in countries with a high production activity, as e.g. the Middle East, and to start to close this gap by conducting first field measurements.
Figure3: Coal mine in Upper Silesia, Poland (Photo: DLR / H. Huntrieser, CC BY-ND-NC 3.0)
Methane is the second most important man-made greenhouse gas after carbon dioxide and has a radiation trapping efficiency of about 80 times higher than CO2 during the first 20 years after its emission. Due to its short lifetime (~10 years) compared to CO2 (~100-1000 years), methane is in the focus of current mitigation policies to reduce global warming, as announced at COP26 in Glasgow (Global Methane Pledge). The data collected will help coal mine operators as well as oil and gas companies and governments to prioritize their actions and policies with the goal to reduce methane emissions worldwide.