Dynamic Assessment of Nature Based Solutions Through Urban Level LCA

Planning Nature Based Solutions (NBS) to address urban challenges requires an approach that embeds the multiple dimensions of NBS to effectively portray their use and impact. Life Cycle Assessment (LCA) provides a comprehensive assessment methodology in this regard. This paper discusses the environmental assessment of NBS via LCA using urban metabolism as an overarching approach to model the urban ecosystem. Performing a dynamic assessment with time series data is suggested as a way of identifying hotspots of the indicators studied within a determined time frame, allowing the assessor to observe and mitigate extremities and make informed decisions on desired temporal patterns. Dynamic assessment is supported by two simulation methodologies: Building Information Modelling for the built environment and Agent Based Modelling for social behavioural patterns.

The goal of this project was to "green" the façade of a building of the Vienna Magistrate ("MA48"), thereby creating ecological niches and habitats for many kinds of insects and birds, and having positive effects on the surrounding indoor and outdoor climates.
The first measurements have shown that the building's heat loss in winter was reduced by up to 50%. The summer cooling through the "green skin" was equivalent to that of about 45 air conditioning units.
Faced with many sustainability challenges, urban assessments help cities to identify main bottlenecks regarding resilience, vulnerability to climate change, food, water and energy security issues and develop sound strategies or policies to tackle these. Through LCA, it is possible to go beyond inventorying direct consumption and emissions, and consider transboundary or cross media effects embedded in urban flows and stocks.
NBS are among the strategies that can benefit from a holistic assessment methodology due to their multiple benefits under themes including greenhouse gas emissions, biodiversity, water, urban food, air and health. The assessment framework targeting NBS should be able to address this multi-layered aspect of NBS.
LCA is a suitable methodology for this purpose as it covers various environmental mechanisms revealing information on different impacts at mid-point and larger scale damage categories at end-point. This is only possible by means of reflecting the complexity of urban systems, which is comprised of numerous layers of functional sub-systems.
To be able to reach the desired level of representation of complex urban systems, the conceptual models developed during system boundary definition stage of LCA can benefit from urban metabolism approach.
Urban metabolism is defined as "a broad range of quantitative methods that attempt to conceptualize urban areas as organisms, requiring goods and energy to maintain functionality and support growth, while emitting waste as a by-product".

Urban Metabolism Definition
Adapted from http://www.sume.at/urban_metabolism LCA should be supplemented with additional tools.
Integrating data generation methods such as BIM and dynamic social assessment can remedy challenging implementation of urban metabolism due to requirement of high amount of data.
ABM is a computational tool that studies how macro effects emerge from micro scale behavioral patterns among heterogeneous social agents, which are evolving, autonomous and interacting. This includes the spatial urban data in the form of GIS, BIM and CIM, material and energy flow data following urban metabolism approach, as well as weather and climate related time series data especially if climate change resilience is studied.

Nature4Cities
Developing an integrated assessment platform for NBS Nature4Cities aims to integrate multiple tools with techniques and modeling abilities at different scales within a single platform that covers economic, social and environmental aspects of NBS.
The environmental assessment module is planned to handle the relation between the urban metabolism and social wellbeing through ABM along with LCA for the assessment of environmental impacts.
The dynamic assessment will cover the changing nature of this interaction. Supply of flows and behaviors of the population influences the decisions, resulting in changes in the settlement patterns and creating or reducing demand in the flows over time. This approach is invaluable for assessing the most desired effects of NBS such as o Urban heat island mitigation in areas with high reflectivity surfaces and dense population o Pollution control in areas with high energy consumption or density o Other local ecosystem services such as biodiversity support o Areas' desirability or accessibility for urban agents and behavioral impact (with the aid of ABM). Nature4Cities project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 730468