Quantifying city-scale carbon emissions of the construction sector based on multi-regional input-output analysis

Abstract

Cities are open systems that rely heavily on external trade and release carbon dioxide (CO2)as a predominant by-product. Quantification of trans-boundary emissions is essential, especially for the construction sector, which requires great intermediate inputs from upstream sectors locally and globally. This study investigates the global energy-related CO2 emissions induced by Hong Kong's construction consumption based on multi-regional input-output analysis for the years 2004, 2007, and 2011. The results showed that the consumption-based CO2 emissions emitted to sustain the local construction consumption are at least 32.37% higher than those estimated by the conventional approach. The consumption-based CO2 has slightly declined from 2004 to 2011. This trend was closely tied to decreasing emission intensities of upstream sectors, even with strong growth in construction final demand. 96.61–97.41% of the consumption-based CO2 were indirect emissions, and 73.50–78.58% were trans-boundary emissions. Utilities, Manufacturing, and Transport & Storage were the main source sectors contributing the most to total CO2 emissions. Based on the results, extended emission monitoring beyond municipal boundaries, diversification of import origins, implementation of import substitution, use of low carbon-intensive materials, and enhancement in electricity generation towards low-carbon fuels are proposed to mitigate construction-related CO2 emissions.