The impact of life cycle assessment database selection on embodied carbon estimation of buildings

Reliable and accurate carbon assessment of a building is becoming increasingly important along with carbon neutrality goals. Although various life cycle assessment (LCA) databases have been adopted for assessing buildings' embodied carbon, the results displayed inconsistencies and the reasons behind the differences were not well revealed. This study aims to identify the critical factors contributing to the inconsistencies by analyzing 20 databases and explore their numerical influences at the three levels of buildings' products, i.e., material, component and unit levels. Using a four-principle framework, it was found that ecoinvent, AusLCI, and Global Digital EPD performed preeminently in flexibility, comprehensiveness, transparency, and uniformity. The quantitative analysis of a case building indicated that the numerical influences by different databases would be higher when evaluating a material compared with a more comprehensive building product (e.g., component or unit). For a concrete building, the emission factors of steel affected the total carbon a lot. The results suggested the importance of cautiously selecting a proper database and clearly clarifying the background information at the initial stage of carbon assessment, under the guidance of the four-step LCA framework (i.e., goal and scope definition, inventory analysis, life cycle impact assessment, and interpretation). By developing a systematic construct including qualitative and quantitative approaches, this study clarified the underlying reasons leading to inconsistencies by LCA databases. It facilitated a better way for professional and non-professional users to select a more suitable carbon assessment database according to their purpose.