Comment on egusphere-2026-3797

Abstract

Abstract. Routine, passive monitoring using satellite sensors offers an effective means of understanding the location, frequency and intensity of industrial methane emissions. Satellites have been used largely to identify fugitive point source emissions in sectors such as oil and gas, but their efficacy for more diffuse sources such as landfills is less established, and formal integration into official reporting and compliance frameworks has yet to be achieved. A persistent methane hotspot originating from Madrid was identified using TROPOMI, where it remains one of the largest signals in Europe. Two landfills, Las Dehesas and Pinto, were identified as significant contributors based on GHGSat observations. This study presents a comprehensive analysis of the TROPOMI and GHGSat observational record up to 2024 for Madrid, alongside aircraft observations, all contextualised against previous short-term studies, facility-scale reporting, and gridded inventories. Plume-based city-scale emissions averaged 13 ± 9 t/hr from TROPOMI compared to ~8 t/hr from the gridded inventories. Facility-scale emissions ranged from 2.5 ± 1.3 t/hr (Las Dehesas) and 3.8 ± 2.0 t/hr (Pinto) from GHGSat, and 3.0 ± 1.8 to 4.6 ± 2.7 t/hr respectively from aircraft, compared to reported averages of 0.4 and 1.0 t/hr between 2018–2024. Measurement-derived rates exceeded reported estimates by a factor of 0.5–6, highlighting a severe gap between bottom-up inventory and top-down observational approaches. We discuss challenges associated with satellite interpretation and meteorology, connect emissions to on-site management practices, and make recommendations towards operational use of these datasets.

Authors 11

1. Daniel A. Potts

   University of Leicester

   Affiliation as printed

   University of Leicester, UK

2. Harjinder Sembhi

   University of Leicester

   Affiliation as printed

   University of Leicester, UK

3. Matthieu Dogniaux Aachen SRON Space Research Organisation Netherlands

   Space Research Organisation Netherlands

   Affiliation as printed

   SRON Space Research Organisation Netherlands, Leiden, the Netherlands

4. Joannes D. Maasakkers Aachen SRON Space Research Organisation Netherlands

   Space Research Organisation Netherlands

   Affiliation as printed

   SRON Space Research Organisation Netherlands, Leiden, the Netherlands

5. Berend J. Schuit Aachen SRON Space Research Organisation Netherlands

   Space Research Organisation Netherlands

   Affiliation as printed

   SRON Space Research Organisation Netherlands, Leiden, the Netherlands

6. Dirk Schuettemeyer

   European Space Agency

   Affiliation as printed

   European Space Agency

7. Timon Hummel

   European Space Agency

   Affiliation as printed

   European Space Agency

8. Rocio Barrio Guillo

   University of Leicester

   Affiliation as printed

   University of Leicester, UK

9. Oliver Schneising

   University of Bremen

   Affiliation as printed

   Institute of Environmental Physics, University of Bremen, Bremen, Germany

10. Luis Guanter

    Universitat Politècnica de València

    Affiliation as printed

    Universitat Politècnica de València (UPV), Spain

11. Ilse Aben Aachen SRON Space Research Organisation Netherlands

    Space Research Organisation Netherlands

    Affiliation as printed

    SRON Space Research Organisation Netherlands, Leiden, the Netherlands