Evaluating the embodied carbon of building materials imported to Hong Kong

Abstract

The rapid growth of the construction industry prompts the interregional imports of building materials, leading to the embodied carbon (EC) transfers. Previous studies evaluated trade-driven EC through Input-Output analysis or focused on individual products, lacking the detailed analysis of EC of building material at the product level. This study examines the EC in the import of 52 building material commodities to Hong Kong in 2012–2021. The EC is calculated by multiplying the quantities of imported building materials by the emission factor for their production in the exporters. The import quantity data are obtained and validated by local and international trading statistics, while the emission factors are collected from the literature and relevant life cycle database (e.g. Ecoinvent). The results show that the EC was between 3.18 and 6.76 Mt/a over the ten years, equivalent to 7.5–17.7% of operational emissions in Hong Kong's construction sector. The EC transfer to Mainland China is found the most significant, accounting for 58.7–76.1% of the total, followed by that to Japan, Taiwan of China, and Vietnam. This uneven EC transfers mainly result from various quantities and types of imported materials from different exporters. The EC per import value is unevenly transferred, ranging from 4.05 to over 2000 g/HKD. The EC mitigation effects of the material efficiency measure were generally negative, ranging from −1.80 to 0.23 Mt. Meanwhile, the EC mitigation effects of the cleaner production measure of materials were continuously positive, from 0.03 to 0.33 Mt. This study proposes the methodology to quantify the trade-driven EC and support the classification of consumption-based responsibility of the construction sector in Hong Kong and beyond.