Estimating CH<sub>4</sub>, CO<sub>2</sub> and CO emissions from coal mining and industrial activities in the Upper Silesian Coal Basin using an aircraft-based mass balance approach

Abstract

Abstract. A severe reduction of greenhouse gas emissions is necessary to reach the objectives of the Paris Agreement. The implementation and continuous evaluation of mitigation measures requires regular independent information on emissions of the two main anthropogenic greenhouse gases, carbon dioxide (CO2) and methane (CH4). Our aim is to employ an observation-based method to determine regional-scale greenhouse gas emission estimates with high accuracy. We use aircraft- and ground-based in situ observations of CH4, CO2, carbon monoxide (CO), and wind speed from two research flights over the Upper Silesian Coal Basin (USCB), Poland, in summer 2018. The flights were performed as a part of the Carbon Dioxide and Methane (CoMet) mission above this European CH4 emission hot-spot region. A kriging algorithm interpolates the observed concentrations between the downwind transects of the trace gas plume, and then the mass flux through this plane is calculated. Finally, statistic and systematic uncertainties are calculated from measurement uncertainties and through several sensitivity tests, respectively. For the two selected flights, the in-situ-derived annual CH4 emission estimates are 13.8±4.3 and 15.1±4.0 kg s−1, which are well within the range of emission inventories. The regional emission estimates of CO2, which were determined to be 1.21±0.75 and 1.12±0.38 t s−1, are in the lower range of emission inventories. CO mass balance emissions of 10.1±3.6 and 10.7±4.4 kg s−1 for the USCB are slightly higher than the emission inventory values. The CH4 emission estimate has a relative error of 26 %–31 %, the CO2 estimate of 37 %–62 %, and the CO estimate of 36 %–41 %. These errors mainly result from the uncertainty of atmospheric background mole fractions and the changing planetary boundary layer height during the morning flight. In the case of CO2, biospheric fluxes also add to the uncertainty and hamper the assessment of emission inventories. These emission estimates characterize the USCB and help to verify emission inventories and develop climate mitigation strategies.

In situ observations of greenhouse gases over Europe during the CoMet 1.0 campaign aboard the HALO aircraft

“…The core of the device is a modified commercial analyser G2401-m, developed by Picarro Inc. (Santa Clara, CA, USA), which was redesigned in order to fulfil conditions necessary for long-term deployment in the scope of IAGOS ERI (In-service Aircraft for a Global Observing System -European Research Infrastructure). Detailed development of the instrument, with the description of its operational parameters, is described in Chen et al (2010) and Filges et al (2015Filges et al ( , 2018. Here, only the basic operation principle and main differences to the IAGOS setup are given.…”

“…The instrument reports dry mole fractions, defined as the number of molecules of each species in moles per one mole of dry air, with typical observed ranges expressed in micromoles per mole (µmol mol −1 ) for CO 2 (equal to 1 part per million, ppm) and in nanomoles per mole (nmol mol − 1) for CO and CH 4 (equal to 1 part per billion, ppb). As the collected air was not dried in the sampling line, a water correction was applied based on the online measurements of the H 2 O mole fraction, following the approach described in previous studies of Filges et al (2015) and Reum et al (2019).…”

“…Except for a single calibration check performed prior to take-off during a power-up procedure, all the other calibration check cycles were enabled manually by an onboard operator of the system, during transit phases of the flight, in contrast to the regular IAGOS implementation (Filges et al, 2015(Filges et al, , 2018. The in-flight calibration checks occurred at high altitudes, where high gradients of GHGs were not expected and the loss of information could be minimised.…”

“…Results from in-flight measurements of the two reference cylinders showed no significant drift; however the flightto-flight variation of each low-and high-span measurement during the period prior to the instrument malfunction on 7 June was slightly larger than expected for CO 2 : low-span measurements varied by 0.10 µmol mol −1 , 0.4 nmol mol −1 and 1.0 nmol mol −1 , while high-span measurements varied by 0.14 µmol mol −1 , 0.3 nmol mol −1 and 0.8 nmol mol −1 for CO 2 , CH 4 and CO, respectively. The likely cause for this is the silicon rubber membranes used in the pressure regulators (Filges et al, 2015), which are known to cause diffusion of CO 2 (Hughes and Jiang, 1995). Given that species other than CO 2 did not show unexpected behaviour, we did not apply any correction of the measurements resulting from the inflight measurements of the reference cylinders.…”

Estimating Upper Silesian coal mine methane emissions from airborne in situ observations and dispersion modeling

“…Recently, Luther et al (2019) reported on XCH4 flux estimates ranging from 6 ± 1 kt CH 4 yr −1 for single shafts to up to 109 ± 33 kt CH 4 yr −1 for a subregion of the USCB from ground-based, portable, sun-viewing Fourier transform spectrometers mounted on a truck. Fiehn et al (2020) investigated CH 4 emissions from the USCB using a mass balance approach. They report emission estimates of 436 ± 115 and 477 ± 101 kt CH 4 yr −1 from two research flights along with a detailed uncertainty analysis.…”