Material metabolism of residential buildings in Sweden: Material intensity database, stocks and flows, and spatial analysis

Sammanfattning: Construction materials are used for the expansion and maintenance of the built environment. In the last century, construction material stock has increased globally 23-fold. Given the current situation, the accumulated stock can be viewed as a repository of anthropogenic resources, which at the end of life could be re-circulated through the economic system to minimize the inflow of raw materials and the outflow of waste. A major step toward increased material circularity is the development of the supporting knowledge infrastructure. For this reason, research has focused on developing methods intended for exposing the material metabolism, namely, estimating the stocks and flows and analyzing the spatial and temporal dynamics of stocks and flows. Residential buildings comprise a large share of the built environment. However, the material metabolism of these structures has remained unknown in many geographical contexts. Therefore, in this thesis, a bottom-up approach is employed to uncover the metabolism of residential buildings in Sweden. This goal is achieved through three methodological steps. First, a material intensity database is assembled based on architectural drawings of 46 residential buildings built within the period 1880–2010 in Sweden. Second, the stocks and flows are modeled with spatial and statistical inventory data and the developed material intensity database. Third, new spatial analysis approaches to the stocks and flows are conducted within urban and national boundaries. For the urban context, material stock indicators defined at the neighborhood level are clustered with well-known algorithms. At the national level, eight settlement types are considered to indicate the spatial dynamics. The developed database indicates historical trends in terms of the material intensity and composition for residential buildings in Sweden. Moreover, the results contribute to establishing a global database and, through an extended international cross-comparison, to the understanding of how the material intensity and composition of residential buildings differ geographically. Furthermore, the stocks and flows are estimated in million metric tons at different administrative boundary levels. Among the six categories considered, mineral-binding materials, such as concrete, comprise the largest share of the accumulated stock. Finally, spatial differences in material stock composition are depicted in urban geography and nationally, among the eight settlement types. At national level, densely built-up corridors are identified, which should be used for enhancing material circularity. This thesis contributes with data source exploration, methodological development, and critical analyses, relevant to researchers, policy makers, and practitioners interested in a more sustained metabolism of construction materials in the built environment.