Abstract Body

The aim of circular economy is to avoid the use of virgin materials in particular by recycling, reusing and extending the service life of products. Managing existing anthropogenic material stocks is of central importance in order to achieve this. A major part of the anthropogenic material flows are induced from and stocked in the built environment. This results in multiple and complex local and global sustainability challenges. Circular economy concepts have to cope with this complexity and are to be conceived in such a way that negative trade-offs will be avoided. In this respect, the Nexus approach provides a strong concept for structuring and addressing complex relationships between different environmental dimensions.

In this contribution, we exemplify the benefits of Nexus thinking to systematically consider complex interrelationships between different environmental impact dimensions of circular economy applications in the built environment. This helps to identify and mitigate negative trade-offs and developments, and to exploit positive synergies.

We start to adapt the Nexus approach to an application in built environment circular economy analysis by translating the typical Nexus components to soil, energy/climate, water, and waste, and pointing out general relationships between them. In a second step these model relations are underpinned with empirical findings reported in literature and in particular from our own research. Two case studies are presented: One case study with a more general perspective on options of circular handling/recycling of excavated soil and rocks and a second more differentiated case study on concrete recycling, which goes into the details of particular process chains. In addition to this technical/physical perspective we also discuss social considerations as a crosscutting extension of the Nexus approach

The findings confirm that the Nexus concept is excellently suited to systematically consider complex linkages of circular economy environmental impacts. A comprehensive Nexus thinking approach can help to advance a responsible implementation of technical circular built environment solutions and should be pursued much more consistently. So far, however, such approaches are rather the exception – in particular with respect to the consideration of the social dimension.