Built environment stocks (i.e., buildings and infrastructure) play multiple roles in our socio-economic metabolism. They represent an extensive reservoir of secondary raw materials, provide essential services to citizens, drive the material cycles throughout the economy, and entail temporal and spatial lock-ins on energy use and emissions. While research on built environment stocks has boomed in the last decade, the review of existing literature highlighted the need for more spatially refined case studies, particularly of urban areas, to further analyze the patterns, drivers, and implications of built environment stocks.
This thesis aims at weighing the importance of urban built environment stocks for sustainability strategies, using Odense, third city of Denmark, as a case city. First, the urban metabolism of the four main Danish cities was assessed; results showed that Danish cities’ metabolisms have been downsizing but a lack of detailed understanding of the inner workings of cities hindered further exploration of potential improvement.
Odense’s built environment stocks were then characterized in terms of type, quantity, and location of construction materials, through a bottom-up approach integrating geographical information system. In total, 66.7 megatons (or 329 tons per capita) of construction materials are stocked in the city. Spatially refined and detailed results were found to support the development of resource recovery strategies such as urban mining and circular economy.
These results were used to calculate the carbon replacement value of the city, which amounts to 10.5 megatons of CO2 equivalent (or 52 tons per capita), corresponding to 13 years of the city’s operational emissions. Such stock-related indicator allowed to better understand the socio-economic metabolism of the city, and highlighted the potential of secondary material recovery for decarbonization.
Finally, a qualitative investigation highlighted the importance of built environment stocks for fulfilling human basic needs. But the building of new urban stock in a similar way than Odense would result in considerable carbon emissions, thus stressing an urgent need for more carbon- and resource efficiency in the built environment.
Recommendation for further research include the development of material intensity coefficient for nonresidential buildings, and more spatially refined case studies so as to facilitate the analysis of intricate drivers (e.g. urban forms, human well-being) and implications (e.g. carbon replacement value) of material stock accumulation in the built environment.
University of Southern Denmark, Department of Green Technology