Tracking urban carbon footprints from production and consumption perspectives
Jianyi Lin, Yuanchao Hu, Shenghui Cui, Jiefeng Kang, Anu Ramaswami
 
Tracking urban carbon footprints from production and consumption perspectives
    Cities are hotspots of socio-economic activities and greenhouse gas emissions. The aim of this study was to extend the research range of the urban carbonfootprint (CF) to cover emissions embodied in products traded among regions and intra-city sectors. UsingXiamen City as a study case, the total urban-related emissions were evaluated, and the carbon flows among regions and intra-city sectors were tracked. Then five urban CF accountings were evaluated, including purely geographic accounting (PGA), communitywide infrastructurefootprint (CIF), and consumption-basedfootprint (CBF) methods, as well as the newly defined production-basedfootprint (PBF) and purely productionfootprint (PPF). Research results show that the total urban-related emissions of Xiamen City in 2010 were 55.2Mt CO2e/y, of which total carbon flow among regions or intra-city sectors accountedfor 53.7Mt CO2e/y.Within the total carbonflow, import and export respectively accountedfor 59 and 65%, highlighting the importance of emissions embodied in trade. By regional trade balance, North America and Europe were the largest net carbon exported-to regions, andMainland China and Taiwan the largest net carbon imported-from regions. Among intra-sector carbon flows, manufacturing was the largest emission-consuming sector of the total urban carbon flow, accountingfor 77.4, and 98% of carbon export was through industrial products trade. By the PBF, PPF, CIF, PGA and CBFmethods, the urban CFs were respectively 53.7Mt CO2e/y, 44.8Mt CO2e/y, 28.4Mt CO2e/y, 23.7Mt CO2e/y, and 19.0Mt CO2e/y, so all of the otherfour CFs were higher than the CBF. All of these results indicate that urban carbon mitigation must consider the supply chain management of imported goods, the production efficiency within the city, the consumption patterns of urban consumers, and the responsibility ofthe ultimate consumers outside the city.