Combining circular and LCA indicators for the early design of urban projects

Abstract

The built environment is a key sector for the transition towards a so-called circular economy, contributing to solve the global environmental challenges humanity is facing. As buildings interact with other sectors like transport and energy, a systemic approach is needed to assess the environmental relevance of circular economy practices. The purpose of this study is to develop and test an approach for the evaluation of overall environmental performance of urban projects. Combining Material Flow Analysis (MFA), the Material Circularity Indicator (MCI), and Life Cycle Assessment (LCA) indicators allows for relating means (material recovery) and performance (protection of human health, biodiversity, and resources). This study shows the ability of LCA to evaluate circular economy practices at the scale of an urban project. It also highlights LCA’s limitations and shows that research is needed to improve resource depletion evaluation and biogenic carbon accounting in eco-design LCA tools. Results show that at the project scale, the MCI, one of the major circular indicators in use today, and MFA provide interesting information complementary to LCA but do not successfully evaluate the environmental performance of circular practices. Circularity indicators are complementary to LCA indicators and should not replace them in the eco-design process. Rather than setting circularity targets for a project, it is advisable to set environmental targets so that designers use circularity combined with other means to reach these targets in a systemic way. The choice and implementation of environmentally sound circular actions and strategies are at stake.