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

University essay from KTH/Byggvetenskap

Abstract: Since the first warnings on the limits of planet Earth, 50 years ago, policies havenot been sufficient and fast enough to create a more sustainable world, which is todayillustrated by climate change, an increase in resource scarcity, and tremendousbiodiversity loss. Cities have been playing an important role in those environmentalconsequences, today accounting for 60% of greenhouse gases. However, citiesare designed by urban planners, who have a great influence on their projects inthe early planning phases. Thus, there is an urge to provide urban planners witheffective decision support tools that allow them to have in-depth knowledge of theenvironmental consequences of their choices.This is the goal of the ”Energy Carbon District”(ECD) methodology implementedin the Urban Print software, a project launched in 2017 by the FrenchAgency for Ecological Transition (ADEME). This tool sets out the first methodologicalchoices for carrying out life cycle analyses at the district level, right fromthe first stages of planning.The goal of this master thesis was to understand the strength and weaknessesof the ECD methodology and Urban Print software, and conduct a district LCAanalysis on a residential neighbourhood in order to get lessons on the most impactingdistricts’ elements, and on the best strategies to reduce those impacts.In this context, the study first provides an extensive literature review on the LCAmethodology, construction products LCA, buildings LCA, and districts LCA. Then,multiple district LCA are conducted on a generic new residential neighbourhoodlocated in Bayonne (France), using different parameters, and different weightingmethodologies.Our case study showed that energy, mobility, and construction products & equipmentare successively the three main contributors to districts’ impacts in a Businessas-usual scenario. ”Energy efficiency” and ”low impacting energy production” werethe two most effective leverages of urban planners to reduce environmental impacts,reducing the total weighed impacts by 21% to 34.6% compared to the Businessas-usual scenario. Once those leverages were activated, mobility and constructionproducts & equipment became the two first contributors, but very few leveragescould be used to reduce those impacts.In the end, the literature review and case study, allowed to highlight the strengthsand weaknesses of the ECD methodology, and the next challenges for district LCAstandardization. One challenge that stands out is the development of tools able toquantify mobility-related impacts based on more district parameters than just thelocation.

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