Supporting biodiversity-sensitive urban regeneration plans through Life Cycle Assessment: A case study in Milan, Italy

Nature-based solutions (NbS) offer effective means to address urban challenges arising from population growth and climate change. Thanks to thoughtful NbS planning, cities can become a source of solutions to these challenges, while also meeting Europe's urban nature targets. Among various evaluation tools, life cycle assessment (LCA) goes beyond the primary scope of NbS (i.e. the provision of Ecosystem Services, ES), and focuses on quantifying the environmental impacts generated over the entire life cycle of the NbS. LCA can thus be used to identify impact leakages and hotspots in the design phase, supporting planners in steering projects toward “net-gain” objectives. This study confirms the methodological potential, as anticipated by the literature, of integrating LCA and ES to promote sustainable NbS implementation in urban planning. It specifically aims to evaluate trade-offs across all life-cycle stages of an urban regeneration system, expressing beneficial support for biodiversity within the LCA framework. The area under study is a university square in Milan-Bicocca, Italy, recently transformed into an intensive green roof that covers an underground indoor space of the university. By merging LCA and ES approaches, it was possible to highlight some of the detrimental and beneficial impacts of this NbS. The standard LCA building assessment modules were expanded to include a module of ES provided throughout the lifespan. Beyond directly combinable ES, such as CO2 storage by trees, a novel compatible methodology was developed to quantify the ES of support to biodiversity, with a focus on pollinators. This allowed for the valorisation of plant species selection in the planning process. Midpoint and endpoint impact assessments were combined to reveal the construction phases and processes that most influence sustainability outcomes. This hotspot analysis highlighted a potential alternative scenario that could reduce the overall detrimental impacts.