SUPERVISOR: Fridolin KRAUSMANN

PROJECT ASSIGNED TO: Magdalena FILTER-PIELER

Over the last century, the world has experienced an unprecedented increase in the extraction and consumption of materials [Krausmann et al., 2017]. Between 1900 and 2010, the annual material input into our socioeconomic system increased more than tenfold [Haas et al., 2020].
Additionally, the way materials are used has changed fundamentally. At the beginning of the 20th century, approximately 80% of all materials were used as food, feed, or fuel. By 2015, this share had dropped to just 42%. This shift means that, by 2015, more than half of all processed materials were used to build material stocks-long-lasting components of our socioeconomic system such as roads, buildings, energy infrastructure, and vehicles. As a result, material stocks increased by a factor of 23 during this period [Krausmann et al., 2017].
Material stocks play a crucial role in the socioeconomic system. Together with complementary flows, they provide essential services such as shelter and transportation. Stocks not only reflect past resource consumption but also shape future material and energy flows, as they can only deliver services in combination with specific material and energy inputs [Haberl et al., 2021]. At low stock levels, an increase in stocks correlates with an increase in services, while at high stock levels, additional stocks do not necessarily improve service quality or well-being [Lin et al., 2017].
This growing demand for materials directly contributes to climate change, as 55% of greenhouse gas (GHG) emissions are linked to material extraction and processing. Material use is also a primary driver of the triple planetary crisis: climate change, biodiversity loss, and pollution [UNEP, 2024].
In recent years, the circular economy (CE) has gained traction in academia and policy-making as a concept to reduce the environmental pressures of socioeconomic activities [Kirchherr et al., 2023]. However, the CE still lacks a clear and universally accepted definition. It is often framed as a shift from the current “take-make-dispose” logic of a linear economy to a system that emphasizes keeping materials within the economic cycle by closing “loops,” such as through increased recycling. More holistic definitions of the CE generally aim to minimize virgin material input, waste, and emissions by slowing, closing, and narrowing material and energy cycles [Kirchherr et al., 2023].
This doctoral project aims to estimate the material and energy requirements, as well as the associated GHG emissions, of future stock scenarios. CE measures are often seen as a key building block for a sustainable economy [European Commission, 2019]. It is therefore crucial to investigate their potentials and limitations to reduce required energy and material flows. To do so I want to use the dynamic Material Flow Analysis (dMFA) model MISO2, which estimates economy-wide stock level on the basis of material flows. The questions I want to answer are: 
• What are potential future pathways for material stock development in the European Union, and      what are their associated energy requirements and GHG emissions?
• To what extent can CE measures that narrow, close, and slow material cycles reduce resource and energy use and GHG emissions for stocks?

On the global level stocks and, with them, services are unequally distributed, with high stock accumulation in the Global North and low stock levels in the Global South [Haberl et al., 2025]. This unequal distribution leads to high material consumption in the Global North and a critical shortage of stocks, below levels required for decent living, in the Global South. Using a stock-driven dMFA model I want to investigate: 

• Aiming to provide universal Decent Living Standards and stay within the 2°C carbon budget, what are possible stock growth trajectories?

 

Haas, Willi, Fridolin Krausmann, Dominik Wiedenhofer, Christian Lauk, and Andreas Mayer. 2020. ‘Spaceship Earth’s Odyssey to a Circular Economy - a Century Long Perspective’. Resources, Conservation and Recycling 163 (December): 105076. https://doi.org/10.1016/j.resconrec.2020.105076.

Haberl, Helmut, Martin Schmid, Willi Haas, Dominik Wiedenhofer, Henrike Rau, and Verena Winiwarter. 2021. ‘Stocks, Flows, Services and Practices: Nexus Approaches to Sustainable Social Metabolism’. Ecological Economics 182 (April): 106949. https://doi.org/10.1016/j.ecolecon.2021.106949.

Haberl, Helmut, André Baumgart, Julian Zeidler, et al. 2025. ‘Weighing the Global Built Environment: High‐resolution Mapping and Quantification of Material Stocks in Buildings’. Journal of Industrial Ecology 29 (1): 159–72. https://doi.org/10.1111/jiec.13585.

Krausmann, Fridolin, Dominik Wiedenhofer, Christian Lauk, et al. 2017. ‘Global Socioeconomic Material Stocks Rise 23-Fold over the 20th Century and Require Half of Annual Resource Use’. Proceedings of the National Academy of Sciences 114 (8): 1880–85. https://doi.org/10.1073/pnas.1613773114.

Kirchherr, Julian, Nan-Hua Nadja Yang, Frederik Schulze-Spüntrup, Maarten J. Heerink, and Kris Hartley. 2023. ‘Conceptualizing the Circular Economy (Revisited): An Analysis of 221 Definitions’. Resources, Conservation and Recycling 194 (July): 107001. https://doi.org/10.1016/j.resconrec.2023.107001.

Lin, Chen, Gang Liu, and Daniel B. Müller. 2017. ‘Characterizing the Role of Built Environment Stocks in Human Development and Emission Growth’. Resources, Conservation and Recycling 123 (August): 67–72. https://doi.org/10.1016/j.resconrec.2016.07.004.

UNEP, ed. 2024. Bend the Trend: Pathways to a Liveable Planet as Resource Use Spikes. Global Resources Outlook 2024. International Resource Panel.