Urban European Methane Emission Characteristics and Insight from CH4 Source Tracers: na

Julianne M Fernandez

Research output: ThesisDoctoral Thesis


Mitigating greenhouse gas emissions is becoming more of a priority in order to slow and reduce positive anthropogenic feedback to climate warming. As a consequence, there has been an increasing interest in understanding urban methane (CH4) emissions around the world. Past research has shown that urban CH4 emissions are influenced by a city's natural gas distribution network (NGDN) and pipeline replacement plans. National inventory estimates for NGDNs are heavily based on population density and may not correctly represent the spatial distribution of high emission locations. Mobile measurement studies can help improve and validate emissions from the energy sector and serve as a tool for effective mitigation planning. Therefore, this research focuses on locating and quantifying urban CH4 emissions of Greater London and Bucharest Romania in comparison with other European cities surveyed around similar times. Also, highlighted are the applications and reliability of three commonly used source tracers, δ13CCH4, δ2HCH4, and C2H6:CH4, with an additional focus on the development of a new δ2HCH4 measurement system.
Presented here are measurements and quantifications of urban CH4 emissions from a western European city (London, UK) and an eastern European city (Bucharest, Romania), which differ culturally, governmentally, and economically. Extensive mobile surveys were conducted from 2018 to 2019, measuring street-level CH4 mole fractions, ethane (C2H6), and analyzing δ13CCH4 and δ2HCH4 for source type attributions.
A total of 969 leak indicators were confirmed in Bucharest, and 925 for London. Compared to other recently measured cities, both Bucharest (1832 tons CH4 yr-1) and London (~2220 tons CH4 yr-1) had greater city-wide emission rates than Paris, France, and Hamburg, Germany. Isotopes (δ13CCH4 & δ2HCH4) and ethane-methane ratios (C2:C1) were used extensively in an attempt to identify emission sources of both cities. In Bucharest, C2:C1 and δ2HCH4 tracers showed the greatest emission dominance from wastewater (58%-63%), while less than half (32%– 42%) were fossil fuel, and 0-5% were pyrogenic. London source tracers indicated a dominance of fossil fuel δ13CCH4 signatures and C2:C1 ratios (86% to 91%), while 7%-14% was biogenic, and only 0% - 2% were pyrogenic. This research will help to guide local governments with emission compliance and to prioritize greenhouse gas mitigation strategies for urban areas. This includes the identification of emissions that can most readily be reduced, helping to achieve the Global Methane Pledge of reducing human-induced emissions 45% by 2030.
Original languageEnglish
Awarding Institution
  • Royal Holloway, University of London
  • Lowry, David, Supervisor
  • Fisher, Rebecca, Supervisor
  • Nisbet, Euan, Supervisor
Award date1 Nov 2022
Publication statusUnpublished - Oct 2022


  • Methane
  • stable Isotopes
  • greenhouse gas
  • Greenhouse gas emissions
  • greenhouse gas mitigation
  • Global Warming
  • Climate warming
  • Urban methane
  • urban emissions

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