Mapping the changes of CH4 emissions in global supply chains

Abstract

This study aims to identify methane (CH4) emission flows along global supply chains from both production- and consumption-based perspectives and their temporal changes from 2000 to 2014. We employed the structural path analysis (SPA) method to examine the embodied CH4 emission trade through inter-sectoral and inter-regional supply chains. Production activities in the sector of Agriculture (such as crop and animal production) and consumption activities in Construction (such as infrastructure) were the most significant contributors to global CH4 emission increases during 2000–2014. Agriculture and Mining (such as coal mining) accounted for large shares of global embodied CH4 trade at the final consumption tier (i.e., the trade of final goods or services), while Food (such as beverages and tobacco) and Heavy manufacturing (such as steel or automobile manufacturing) were significant contributors to embodied CH4 emissions in the trade of intermediate goods or services directly used to produce final goods or services. This finding highlights the different potential of the sectors for CH4 abatement along global supply chains. The United States imported the most embodied CH4 emissions from foreign areas in 2000 in contrast to China, which dominated imports in 2014. Over 80% of China's embodied CH4 emissions in 2014 were related to intermediate production along global supply chains due to industrial upgrading. India surpassed China as the largest direct emitter for producing final goods or services. Given the critical role of non-CO2 greenhouse gases in global climate change, the spatiotemporal changes of CH4 emissions in global supply chains can help explore the justified allocation of reduction responsibility between countries and sectors connected by the chains.