SUPERVISOR: Fridolin KRAUSMANN

PROJECT ASSIGNED TO: André BAUMGART

In the past century, material in-use stocks have increased rapidly. Population growth and wealth accumulation in industrialized countries have been main drivers of urbanization and an unprecedented expansion of infrastructure globally, albeit at largely varying intensity levels across world regions. This requires the mobilization of high quantities of stock-building materials both for the expansion of stocks, as well as their operation, maintenance and replacement. These material flows are in turn associated with energy use, emissions and material losses.

Both stocks and flows are associated with certain physical functions and corresponding services. For example, the residential building stock together with the flows for operation and maintenance provide habitable living space. Roads and vehicle stocks facilitate mobility and the transportation of goods. Consequently, material stocks and the services they provide are essential requirements for the functioning of modern societies and play a key role in the societal transition towards sustainability. However, material stocks, which are associated with certain material and energy use patterns, cause lock-in effects, or path dependencies because a systematic reconfiguration and restructuring is a complex undertaking. It is therefore highly relevant to understand the composition of existing material stocks and their relationship to services.

With the advent of digitalization and the transition to renewable energy technologies, the application of scarce materials such as rare earth elements (REE) in the production of stocks can be expected to increase further in the decades to come. Consequently, from a sustainability perspective, not only bulk materials such as cement, steel or wood are relevant, but also low-quantity materials need to be considered when investigating material accumulation in stocks. So far, these materials have been under researched in stock studies.

In the past, various material stock and flow accounting methods have been applied in order to quantify material stocks and associated flows, mostly focusing on the regional or national level. While many scientific studies have quantified material stocks using a top-down inflow-driven approach, bottom-up material stock modelling has proven to be a well-suited for scenarios due to its spatial explicitness approach and consideration of functions of stocks, which are often out of the scope of in inflow-driven studies. 

The focus of this PhD project is on the application of bottom-up quantification of various material stock types for both bulk and technology-critical materials as this is essential for understanding where stock-building materials accumulate and what the functions, services and disservices of these material stocks and flows are. This understanding is key for the development of prospective scenario where material requirements of specific future stock transformation paths are analyzed. The project will assess how well-suited the application of bottom-up stock models is for various materials at various spatial scales by developing and testing dynamic stock-driven models for various use cases. More concretely, in the PhD project, the approach will be applied to estimate current and future stocks and flows of scarce materials in transportation in Vienna, Austria, as well as bulk material stocks and flows associated with buildings and transport infrastructure at both the national and global level.