Anatomy of methods for measuring life cycle carbon emission of built environment

The built environment, e.g., buildings and infrastructures, is responsible for over 79 % of global carbon emissions, prompting an urgent need to reduce its carbon emissions. Adopting life cycle assessment for buildings and infrastructures to measure their whole life carbon emission is crucial in achieving carbon neutrality. This paper critically examines methods explicitly measuring life cycle carbon emissions of built environment. Various life cycle carbon emission assessment standards are analysed and compared and their differences are quantified in two case studies. It is found that the inconsistent system boundary definitions, biogenic carbon calculation methods and end-of-life modelling methods are obstacles to measuring and managing carbon emissions of the built environment. It is also found that the necessity of developing a unified life cycle carbon emission assessment method for buildings and infrastructure is compelling. Future directions of developing a consistent and accurate life cycle carbon emission assessment method are pointed out. These outcomes will raise the awareness of inconsistency in various methods with a view to accurately measuring carbon emissions of the built environment. • Five international standards for life cycle carbon emission assessment are compared and analysed. • Factors contributing to inconsistency between these standards are evaluated. • Two case studies are used to quantify the difference between assessment results. • The difference between life cycle carbon emission results can reach up to 18 %.