Preprints
https://doi.org/10.5194/amt-2022-134
https://doi.org/10.5194/amt-2022-134
 
09 May 2022
09 May 2022
Status: this preprint is currently under review for the journal AMT.

Intercomparison of detection and quantification methods for methane emissions from the natural gas distribution network in Hamburg, Germany

Hossein Maazallahi1,2, Antonio Delre3, Charlotte Scheutz3, Anders M. Fredenslund3, Stefan Schwietzke4, Hugo Denier van der Gon2, and Thomas Röckmann1 Hossein Maazallahi et al.
  • 1Institute for Marine and Atmospheric research Utrecht (IMAU), Utrecht University (UU), Utrecht, The Netherlands
  • 2Netherlands Organisation for Applied Scientific Research (TNO), Utrecht, the Netherlands
  • 3Department of Environmental Engineering, Technical University of Denmark (DTU), Lyngby, Denmark
  • 4Environmental Defense Fund (EDF), Berlin, Germany

Abstract. In August and September 2020, three different measurement methods for quantifying methane (CH4) emission from leaks in urban gas distribution networks were applied and compared in Hamburg, Germany: the “mobile”, “tracer release” and “suction” methods. The mobile and tracer release methods determine emission rates to the atmosphere from measurements of CH4 mole fractions in the ambient air, and the tracer release method also includes measurement of a gaseous tracer. The suction method determines emission rates by pumping air out of the ground using soil probes that are placed above the suspected leak location. The quantitative intercomparison of the emission rates from the three methods at a small number of locations is challenging because of limitations of the different methods at different types of leak locations.

The mobile method was designed to rapidly quantify the average or total emission rate of many gas leaks in a city, but it yields a large emission rate uncertainty for individual leak locations. Emission rates determined for individual leak locations with the tracer release technique are more precise because the simultaneous measurement of the tracer released at a known rate at the emission source eliminates many of the uncertainties encountered with the mobile method. Nevertheless, care must be taken to properly collocate the tracer release and the leak emission points to avoid biases in emission rate estimates. The suction method could not be completed or applied at locations with widespread subsurface CH4 accumulation, or due to safety measures, and this sampling bias may be associated with a bias towards leak locations with low emission rates. The leak locations where the suction method could not be applied were the biggest emitters as confirmed by the emission rate quantifications using mobile and tracer methods and an engineering method based on leak’s diameter, pipeline overpressure and depth at which the pipeline is buried. The corresponding sampling bias for the suction technique led to a low bias in derived emission rates in this study. It is important that future studies using the suction method account for any leaks not quantifiable with this method in order to avoid biases, especially when used to inform emission inventories.

Hossein Maazallahi et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2022-134', Anonymous Referee #1, 17 May 2022
  • CC1: 'Comment on amt-2022-134', Luise Westphal, 13 Jun 2022
  • RC2: 'Comment on amt-2022-134', Anonymous Referee #2, 07 Aug 2022

Hossein Maazallahi et al.

Data sets

Mobile and tracer measurements Maazallahi, H., Delre, A., Scheutz, C., Fredenslund, A. M., Schwietzke, S., Denier van der Gon, H., Röckmann, T. https://fileshare.icos-cp.eu/s/wTjBngNKfCBi2PL

Hossein Maazallahi et al.

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Short summary
Measurement methods are increasingly deployed to verify reported methane emissions of gas leaks. This study describes unique advantages and limitations of three methods. Two methods are rapidly deployed, but uncertainties and biases exist for some leak locations. In contrast, the suction method could accurately determine leak rates in principle. However, this method, which provides data for the German emission inventory, creates an overall low-bias in our study due to non-random site selection.