International trade from a societal metabolism perspective

摘要: This presentation discusses the role of international trade in the study of material and energy cycles on country, regional, and global scales. With the growing trade flows, the societal metabolisms of different regions have become increasingly interconnected. Understanding trade flows is therefore essential for understanding and shaping the metabolism of our economies to increase resource efficiency and reduce environmental impacts. The basic method for the study of the societal metabolism, Material Flow Analysis (MFA), provides a language that allows scientists to describe physical stocks and flows in natural as well as anthropogenic systems, which is a prerequisite to integrate ecology and economy. The use of MFA is illustrated with an example of the historic iron cycle in the United States. The study shows that international trade of iron units has increased significantly over the last couple of decades, with a net import of iron embodied in goods upstream of the use phase and a net export of downstream products. The present trade balance of iron units shows a net import that is theoretically large enough to establish an iron, steel and scrap industry that is entirely based on recycling. However, there are large uncertainties with respect to the end-of-life fate of products, such as exports of used and discarded products and accumulation in obsolete stocks or landfills. More reliable trade data for used and discarded products could significantly improve our understanding of the iron metabolism and the policy options for resource and environmental management.