Assessing embodied carbon emissions from material consumption in Hong Kong's building sector from 2012 to 2050 under uncertainty

Abstract

Material consumption in building construction contributes to numerous embodied carbon (EC) emissions, and thus assessing this aspect of EC is crucial for tracking the climate change impacts of construction activities. The existence of multiple uncertainty factors leads to deviations of assessment results from reality. This study developed a systematic methodology to assess the material consumption-related EC emissions in the building sector under uncertainty at multiple levels, and applied it in Hong Kong's building sector from 2012 to 2050. Four types of uncertainty factors, namely, floor area of new buildings, material consumption intensity, carbon emission factor, and material recycling quantity, were considered, with their fluctuation intervals determined based on data sources and precision. The Sobol’ sensitivity analysis method was adopted to identify the sensitive factors affecting the EC. Results showed that the annual EC from material consumption peaked at 2.61 Mt in 2018, equivalent to 6.4% of the carbon emissions in Hong Kong. The emissions are estimated to have a rapid decline until 0.02–0.24 Mt in 2050 under different scenarios of accommodation floor area and material recycling. Concrete and steel account for over 80 % of the EC throughout the study period. The uncertainty factors lead to considerable variations in the EC assessment results, with fluctuations ranging up to ±83.7 %. The building sector scale was identified as the dominant factor affecting the EC results in the long term, while the significance of material demand and emission factors diminishes progressively. Based on these findings, we suggest establishing a carbon footprint tracking system for building materials, and implementing a dynamic update and modification mechanism for the decarbonisation targets in Hong Kong's building sector.