Quantifying perfluorocarbon emissions and bridging discrepancies between top-down and bottom-up estimates
: a sustainable development and systems thinking approach.

  • Eleni Michalopoulou

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)


Industrial activity, and namely the aluminium, semiconductor and rare earth smelting industries are reported to be the main emitters of the very potent, greenhouse gases (GHGs) CF4 and C2F6. These GHGs belong to the larger group of GHG called perfluorocarbons (PFCs) and are gases monitored by the Kyoto Protocol. Previous studies demonstrated large discrepancies between the estimates inferred from atmospheric measurements in conjunction with modelling (top-down) and inventory-based estimates (bottom-up). Only ~50% of the global CF4 and 20% of the global C2F6 emissions estimates could be explained by current emissions inventories. These studies also suggest that our understanding of PFC emissions was very poor. This work set out to bridge the gap between these top-down and bottom-up estimates and improve our understanding of current and historic emissions of these potent gases.

Using different methods, this work quantified emissions from each industry, produced updated, industry specific inventories and a global bottom-up inventory for both these gases (CF4 and C2F6) for the period 1990-2017; a global spatial distribution of the PFC emitting facilities from all three industries are also presented. Additionally, the global bottom-up inventory produced through this work was used as a prior estimate field in two different Bayesian modelling techniques: the analytical and the hierarchical method. These methods combine high frequency atmospheric measurements from the AGAGE network and this prior knowledge field to produce regional emissions estimates. Three case studies were used to investigate PFC emissions through these modelling methods; the Australian, the East Asia and the South Korea case studies. Finally, this work uses systems and sustainable development to describe how PFC emissions are a wicked problem and introduces a different framework of understanding and describing these emissions. As part of this theoretical framework, a new impact factor was also developed, the De Minimis Scaling Impact Factor (DMSIF) that weighs the environmental burden of the PFC emissions against the socio-economic benefit of the industry emitting PFCs on a per country, per sector, over time basis.

While discrepancies and uncertainties remain, these bottom-up estimates compiled the most updated inventory of PFC emissions produced to this date. Equally, some of the modelling methods used have not been used in relation to PFC gases before. Finally, the theoretical frameworks and DM impact factor presented have never before been attempted and could play a critical role in future policy making and industrial emission reduction plans
Date of Award24 Mar 2020
Original languageEnglish
Awarding Institution
  • The University of Bristol
SupervisorSimon O'Doherty (Supervisor)

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