In-Use Stock of Copper in Japan Estimated by Bottom-Up Approach

Recently, metal demands in the world, especially, in developing countries have rapidly risen. The recovery of metal scrap for recycling contributes to the conservation of natural resources and the construction of a sound material cycle society. A dynamic material (substance) flow analysis is a useful tool to estimate in-use stock of materials for investigating the potentials of metal scrap recovery in designated areas. However, it is a challenging task to estimate the in-use stock of materials, especially in developing countries, because of lack of data. There are two approaches, a top-down approach and a bottom-up approach, for estimating the in-use stock of materials. Top-down approach uses time-series data of consumption and trade of materials and products' life time distributions, whereas bottom-up approach uses the numbers of product units in the designated area and its material use intensities. In this paper, the copper stock in 7 end-uses in Japan was estimated with the bottom-up approach, and compared with the results obtained with top-down approach in our previous study. The results obtained by the two approaches fairly corresponded with each other. So, it is suggested that complementary use of these two approaches is helpful to estimate in-use stock of materials.