Mining the urban building stock

Traditional mining institutions inventory raw materials in geogenic deposits (resources) and the economically extractable shares (reserves). The reserves are exploited, processed and the commodities flow to the technosphere, where they accumulate in building, infrastructures and consumer goods. These anthropogenic deposits provide the secondary materials of tomorrow. Currently, no harmonized methodology exits to assess material resources/reserves in the technosphere (gap 1). When it comes to buildings as the largest physical capital of economies, the construction & demolition waste has a high potential for recycling. However, knowledge about the dynamics in the building stock are not well known today (gap 2). This prevents secondary material investments from being contrasted with primary materials investments. Such comparison is needed as input for the protection of primary resources and the efficient use of raw materials. To overcome these gaps, the main goal of this project is to test the hypothesis with regard to whether materials in the building sector can be classified as resources/reserves in order to be compared with primary raw materials. The main research questions are: (1) How can material stocks and flows be analyzed with respect to buildings? (2) How can the economic recoverability of materials from CDW flows be evaluated? (3) How can the materials in the building stock/CDW flows be classified in order to enable comparability with classification schemes for primary materials? To achieve the objective, a new methodology will be developed that a) analyses the material inputs, stocks and outputs with respect to the entire building stock in towns, and that b) evaluates the construction & demolition waste flows in view of material recycling. Because of the long lifetime of buildings, long-term periods and changing socio-economic conditions will be considered. The new methodology will be applied to two case study cities, namely Vienna (Austria) and Taipei (China). The results show the development of the urban building stock/flows from the year 1950 to 2000 and provide an outlook for the waste flows from the year 2000 2050. Based on scenarios, the amount of recyclable materials from construction & demolition flows will be assessed. The results support the waste management sector on its way to a comprehensive resource management sector. The new methodology allows priorities regarding recycling and the disposal of construction & demolition waste to be set. The outlook on future recycling materials in terms of quantity and quality is important for the building industry. The results also demonstrate the role of secondary resources for the supply of resources in highly developed economies.

This project explored the spatio-temporal development of the Viennese building stock from 1920 to 2018. With respect to 1920, we produced a digital building age map that shows 80,640 individual buildings and their construction date. With respect to 2018, we produced a digital building age map too, which compiles construction date information from three distinctive sources from the Viennese city administration. Next, we developed an algorithm that uses the building age map from 1920 and 2018 in order to identify buildings that have been demolished, replaced or new constructed between 1920 and 2018. The algorithm was successfully tested for parts of the 18th Viennese district and resulted the construction and demolition rates in this area from 1920 to 2018. In the future, we will apply the algorithm to the entire city area and use the demolition rates from the past to calibrate a model that estimates the demolition waste flows from 1920 to 2050. The predicted demolition waste flows will be evaluated with regard to the recoverability of valuable materials that can be used as secondary raw material. The final outcomes of this research should facilitate capacity planning in the waste management sector and facilitate the management of raw material supply.