Projection of material flows and stocks in the urban transport sector until 2050 – A scenario-based analysis for the city of Vienna

Abstract The transport sector plays a decisive role in climate change mitigation, especially in cities, as it significantly contributes to global resource and energy consumption. Hence, decarbonising this sector is increasingly recognized as an important means of mitigating climate change, which is reflected in numerous smart city initiatives. However, existing studies thereon have focused almost exclusively on energy and CO2, thereby neglecting the consumption of material resources required to transform urban transport systems so as to be compatible with a low carbon future. In this study, we hence investigate the effects of transforming urban transport systems on future material stock and material flows using the city of Vienna as a case study. For this purpose, a material flow analysis for the infrastructure and vehicles required until 2050 has been conducted taking different scenarios into consideration, which are mainly characterized by different modal splits. The results show that different paths of development among the various transport modes significantly affect the overall material stocks and flows. If the modal split remains constant, the road-infrastructure has to be further expended to provide the transport service needed due to the expected increase in population in Vienna. The material stock per capita for the transport system remains constant at around 54 t/capita for this scenario. If the motorized individual transport can be reduced to a share of less than 10% of all trips (today's share amounts to 25%), the material stock per capita decreases to around 47 t/capita in 2050. As this case allows for infrastructure (e.g. parking infrastructure, road lanes) to be dismantled, the annual material demand for maintenance efforts is also reduced by a fifth (to 460 kg/cap/yr). Despite the reduction in material stocks and flows achievable by changing the current modal split, a significant change in the waste composition in terms of the end-of-life vehicles generated is to be expected in the coming decades. Annual quantities of old batteries, for instance, might rise from today's 1.5 kg/capita up to 70 kg/capita. These changes will definitely challenge the waste management sector, but also represent an opportunity for the recovery of valuable resources. Based on the results, it can be concluded that the transformation of an urban transport system towards lower greenhouse gas emissions also has the potential to reduce future material demand and waste generation. However, this requires a change in the modal split, whereas solely moving to a fossil-free vehicle fleet has the contrary effect.