Reducing the environmental impact of new neighbourhoods during early planning stages using life cycle analysis (LCA) : Towards effective decision support tools for settlements projects

Sammanfattning

Since the first warnings on the limits of planet Earth, 50 years ago, policies have not been sufficient and fast enough to create a more sustainable world, which is today illustrated by climate change, an increase in resource scarcity, and tremendous biodiversity loss. Cities have been playing an important role in these environmental consequences, today accounting for 60% of greenhouse gas emissions. However, cities are designed by urban planners, who have a great influence on their projects in the early planning phases. Thus, there is an urgent need to provide urban planners with effective decision support tools that allow them to gain in-depth knowledge of the environmental consequences of their choices. This is the goal of the “Energy Carbon District” (ECD) methodology implemented in the Urban Print software, a project launched in 2017 by the French Agency for Ecological Transition (ADEME). This tool establishes the first methodological framework for carrying out life cycle assessments at the district level, right from the earliest planning stages. The goal of this master’s thesis was to understand the strengths and weaknesses of the ECD methodology and the Urban Print software, and to conduct a district LCA analysis on a residential neighbourhood in order to draw lessons regarding the most impactful district elements and the best strategies to reduce their impacts. In this context, the study first provides an extensive literature review on the LCA methodology, construction product LCAs, building LCAs, and district LCAs. Then, multiple district LCAs are conducted on a generic new residential neighbourhood located in Bayonne (France), using different parameters and weighting methodologies. Our case study showed that energy, mobility, and construction products & equipment are respectively the three main contributors to district impacts in a business-as-usual scenario. “Energy efficiency” and “low-impact energy production” were the two most effective levers available to urban planners to reduce environmental impacts, reducing total weighted impacts by 21% to 34.6% compared to the business-as-usual scenario. Once these levers were activated, mobility and construction products & equipment became the two primary contributors, but very few additional levers could be used to further reduce those impacts. Ultimately, the literature review and case study highlighted both the strengths and weaknesses of the ECD methodology, as well as the next challenges for district LCA standardization. One challenge that stands out is the development of tools capable of quantifying mobility-related impacts based on a wider range of district parameters than location alone.