Material Flow Analysis (MFA) is a tool used in industrial ecology that allows for accounting for stocks and flows within a spatially and temporally defined system. This dissertation explores the potential of MFA by conducting comprehensive and novel material flow analyses, and by applying these insights to a series of related research questions, namely energy use in metal production, Markov Chain modeling, and the definition of recycling indicators. This study also presents a new way of visualizing MFA results through a circular display for metal life cycles. The circular display proves to be a powerful tool in communicating results in an intuitive way to expert and non-expert stakeholders alike. Case studies are nickel and stainless steel whose global cycles were characterized for years 2000 and 2005, encompassing 50 and more countries and the world. The life cycles of the two metals are linked by nickel’s role as a major alloying element in most stainless steels. Between 2000 and 2005, the global use of both metals grew, driven by China’s extraordinary growth and despite the fact that many industrialized countries decreased their metal use during that time. This study also analyzes challenges in metal recycling, including economic, societal, and technological factors. These challenges are illustrated using the example of nickel and include metal efficiencies across their entire life cycle, and challenges at end-of-life through inefficient separation, leading to non-functional recycling. The results of this study go beyond nickel and stainless steel in that insights gained into recycling challenges are of high relevance for many other metals, too. One of these challenges, the issue of non-functional recycling is still often underestimated, and by highlighting it this study hopes to create awareness for countermeasures to be taken.
Technische Universität Berlin, Germany
Prof. Vera Susanne Rotter, Prof. Thomas E. Graedel