A critical review of life cycle assessment benchmarking methodologies for construction materials

As it stands, the construction sector accounts for a significant proportion of global emissions. The majority of these emissions can be associated with material production. As a result, the importance of quantifying these environmental impacts is continually increasing. However, there is a current lack of guidance and methodologies regarding how to benchmark the impacts of construction products, and thus achieve more transparent environmental reporting and decision-making. Therefore, the aim of this study was to review engineering life-cycle assessment (LCA) literature and applicable standards to identify the key methodological variables required and the key steps for a sector-wide methodology. This was carried out via a bibliographic search for indexed, peer-reviewed journal publications and conference proceedings, project reports, and standards for constructed assets. From the search conducted, 23 documents and 4 standards were selected for review as relevant for this study. As a result, five key constituent methodological variables (study scope; model typology; benchmark approach; database selection; benchmark type) and three key steps (data collection; LCA; benchmark generation, with the option for Data Envelopment Analysis) were identified. Furthermore, considering the novel ISO 21678:2020, specific benchmark pathways were defined for the four types of benchmark values which can be obtained: limit, reference, short- and long-term. The definition of this set of steps, key methodological variables and the authors' recommendations for the construction sector constitute the first LCA benchmarking methodology on this field.