A Framework for Addressing Circularity Challenges in Cities with Nature-Based Solutions

Abstract

A novel framework is presented that aims to guide practitioners and decision makers toward a better understanding of the role of nature-based solutions (NBS) in the enhancement of resources management in cities, and the mainstreaming of NBS in the urban fabric. Existing frameworks describing the use of NBS to address urban challenges do not specifically consider circularity challenges. Thus, the new framework provides the following: (1) a comprehensive set of Urban Circularity Challenges (UCCs); (2) a set of more than fifty NBS units and NBS interventions thoroughly assessed in terms of their potential to address UCCs; and (3) an analysis of input and output resource streams, which are both required for and produced during operation of NBS. The new framework aims to facilitate the coupling of individual NBS units and NBS interventions with NBS that enable circular economy solutions.

Towards a Cross-Sectoral View of Nature-Based Solutions for Enabling Circular Cities

“…The list of NBS_u/i and S_u presented in Langergraber et al [13] and Castellar et al [18] was used as a basis for evaluating their relevance for the following urban sectors: building systems, building sites, urban water management, resource recovery, and urban farming. In this paper, urban sectors also correspond to the working groups of the COST Action Circular City, whereby the evaluation for the overall sector of built environment was separately done for building systems (the building itself) and building sites (including the surroundings of buildings).…”

“…The extent to which NBS_u/i can address multiple urban sectors was based on the methodology presented by Langergraber et al [13] to evaluate the potential of NBSs to address UCCs. In this sense, the selected NBSs for each urban sector were evaluated according to the following scores: (1) the NBS_u/i are relevant (score = 1); (2) the NBS_u/i might be relevant, depending on the system design (score = 0.5); (3) the NBS_u/i is not relevant (score = 0).…”

“…A short questionnaire was developed and sent to the participants of the 10 workshops held between March 2020 and April 2021, during which the new framework [13] of the COST Action Circular City was discussed and developed, to analyze the disciplines that contributed (one workshop was held in person, and the remaining nine workshops were held in a virtual setting). Each virtual Circular City workshop had an average of 71 participants-with a minimal participation of 59 members (second and third virtual workshops) and a maximal participation of 87 members (fifth virtual workshop)-from 28 countries.…”

“…These reviews were prepared by the five Working Groups of the Action, i.e., built environment (WG1 [8]), urban water (WG2 [9]), resource recovery (WG3 [10]), urban farming (WG4 [11]), and transformation tools (WG5 [12]). Furthermore, a framework for addressing UCCs with NBSs was defined [13]. The framework is aimed at mainstreaming the use of NBS for the enhancement of resource management in urban settlements.…”

“…Built environment: Pearlmutter et al [14] focused on building systems and identified the "wicked problem of water"; more provision of services by NBSs requires a higher water use, which is commonly solved by importing water from outside the city. The authors proposed to challenge this conundrum by focusing on those NBS_u/i classified as vertical greening systems and green roofs [13], and how they can be used to foster graywater reuse and capture available rainwater. This approach is based on the first and second urban circularity challenges (UCC 1 and UCC 2 ) [6] and is based on three steps: (i) how can NBS be integrated into buildings help to close the water cycle, (ii) how can water be incorporated into the life-cycle analysis (LCA) of a building as a resource, and (iii) how can the proposed solutions of graywater and rainwater reuse across different climates be modeled to allow comparisons.…”