Closing water cycles in the built environment through nature‐based solutions: The contribution of vertical greening systems and green roofs

David Pearlmutter, Bernhard Pucher, Cristina S.C. Calheiros, Karin A. Hoffmann, Andreas Aicher, Pedro Pinho, Alessandro Stracqualursi, Alisa Korolova, Alma Pobric, Ana Galvão, Ayça Tokuç, Bilge Bas, Dimitra Theochari, Dragan Milosevic, Emanuela Giancola, Gaetano Bertino, Joana A.C. Castellar, Julia Flaszynska, Makbulenur Onur, Mari Carmen Garcia MateoMaria Beatrice Andreucci, Maria Milousi, Mariana Fonseca, Sara Di Lonardo, Veronika Gezik, Ulrike Pitha, Thomas Nehls

Research output: Contribution to journalArticlepeer-review

35 Scopus citations


Water in the city is typically exploited in a linear process, in which most of it is polluted, treated, and discharged; during this process, valuable nutrients are lost in the treatment process instead of being cycled back and used in urban agriculture or green space. The purpose of this paper is to advance a new paradigm to close water cycles in cities via the implementation of nature‐based solutions units (NBS_u), with a particular focus on building greening elements, such as green roofs (GRs) and vertical greening systems (VGS). The hypothesis is that such “circular systems” can provide substantial ecosystem services and minimize environmental degradation. Our method is twofold: we first examine these systems from a life‐cycle point of view, assessing not only the inputs of conventional and alternative materials, but the ongoing input of water that is required for irrigation. Secondly, the evapotranspiration performance of VGS in Copenhagen, Berlin, Lisbon, Rome, Istanbul, and Tel Aviv, cities with different climatic, architectural, and sociocultural contexts have been simulated using a verticalized ET0 approach, assessing rainwater runoff and greywater as irrigation resources. The water cycling performance of VGS in the mentioned cities would be sufficient at recycling 44% (Lisbon) to 100% (Berlin, Istanbul) of all accruing rainwater roof–runoff, if water shortages in dry months are bridged by greywater. Then, 27–53% of the greywater accruing in a building could be managed on its greened surface. In conclusion, we address the gaps in the current knowledge and policies identified in the different stages of analyses, such as the lack of comprehensive life cycle assessment studies that quantify the complete “water footprint” of building greening systems.

Original languageEnglish
Article number2165
JournalWater (Switzerland)
Issue number16
StatePublished - 2 Aug 2021


  • Building greening
  • Built environment
  • Circular cities
  • Green roofs
  • Life‐cycle assessment
  • Nature‐based solutions
  • Vertical greening systems
  • Water cycle
  • Water management
  • Water reuse

ASJC Scopus subject areas

  • Water Science and Technology
  • Geography, Planning and Development
  • Aquatic Science
  • Biochemistry


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