Improving the completeness of product carbon footprints using a global link input-output model: The case of Japan

This paper is concerned with the main activities of Japan's 'Disclosure of CO₂ emissions' programme, aimed at illustrating the CO₂ emissions associated with consumer products as a 'carbon footprint' (CF). Although the current, provisional guidelines for calculating product carbon footprints specify that only the bottom-up approach is to be used for this purpose, this paper presents useful applications of input-output analysis that can improve the reliability of the method considerably, by taking full advantage of the strengths of input-output analysis. To this end, we first estimated the global carbon footprint (GCF) of food and consumables in Japan, using a global link input-output (GLIO) model comprising 804 economic sectors in Japan and 230 foreign countries and regions. By visualizing the GCF on a world map, the global distribution (including Middle East and African countries) of the induced CO₂ emissions of each of the Japanese sectors were identified. To investigate the scope for reducing the data collection burden for CF practitioners, GCFs were compared with CFs obtained using a single-region input-output model. This showed that there are certain commodity groups with a CF equating to 70% to over 90% of the corresponding GCF, even if the imported goods used for producing a Japanese domestic product are considered environmentally equivalent to their domestically produced counterparts. Furthermore, it was identified which data should preferably be collected by the bottom-up approach to secure CO₂ emissions coverage greater than a certain predefined level and keep data and labour costs at a minimum.