Methane Emission Source Attribution and Quantification for Munich Oktoberfest

Abstract

<p>Up to now, festivals have not been considered a significant methane (CH<sub>4</sub>) emission source and events with a limited duration were not included in the emission inventories. We have intensively investigated the Munich Oktoberfest, the world’s largest folk festival, for two consecutive years. Oktoberfest is a potential source for CH<sub>4</sub> as a high amount of natural gas (about 200,000 m³) for cooking and heating is used.</p><p>The results from our 2018 investigation show that CH<sub>4</sub> emissions at Oktoberfest not only come from human biogenic emissions. It is more likely that fossil-fuel related emissions are the major contributors to the Oktoberfest emissions (Chen et al. 2019). In 2019, our goal was to look closer into the source attribution. We used both a portable gas measurement system (LI-COR LI‑7810 Trace Gas Analyzer) in a backpack to measure the CH<sub>4</sub> concentrations, and air sampling bags to examine the ethane/methane ratio and isotopic composition of the exhaust gas (δ13C, δD).</p><p>We walked around the perimeter of Oktoberfest to measure the CH<sub>4</sub> concentration upwind and downwind of the Oktoberfest premises for several hours each day during the two-week festival. In addition, we entered the festival with our instrument to investigate the emission hotspots, i.e. tents and booths, thoroughly. The measurements were carried out both during and after the time of the festival to compare the differences in emission strength and distribution.</p><p>The backpack measurements around the Oktoberfest perimeter show enhancements up to several hundred ppb compared to background values and measurements performed after the festival. The concentration enhancements on the premises were even higher: up to 3,000 ppb for hotspot regions. The ethane/methane ratios and isotopic measurements show clear indications that the emission sources are thermogenic.</p><p>Furthermore, a CFD (Computational Fluid Dynamics) simulation was developed to simulate the gas dispersion within and around the terrain. The simulation uses Reynolds-Averaged Navier-Stokes equations and the k-ε turbulence model for the fluid flow. Wind speed and direction measurements taken close to the festival area were used as the boundary conditions. The dispersion of methane is solved afterwards using the unsteady convection-diffusion equation.</p><p>We will present the strengths and spatial/temporal distributions of the Oktoberfest emissions, assessed using the backpack measurements combined with a CFD model. Further, a comparison between the results of two consecutive years will be given. </p><p> </p><p>Chen, J., Dietrich, F., Maazallahi, H., Forstmaier, A., Winkler, D., Hofmann, M. E. G., Denier van der Gon, H., and Röckmann, T.: Methane Emissions from the Munich Oktoberfest, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2019-709, in review, 2019</p>

Munich permanent urban greenhouse gas column observing network

“…Especially for urban areas, which contribute to more than 70 % of GHG emissions (Gurney et al, 2015) and are therefore hotspots, there is a lack of accurate assessments of emissions. The city emission inventories often underestimate the emissions as there exist unknown emission sources that are not yet included in the inventories (Chen et al, 2020;Plant et al, 2019;McKain et al, 2015).…”