日本におけるディスプロシウムの物質フロー分析

Abstract

Recently, recycling of rare metals has been of great interest because of the rapid growth in their demands. Substance flow analysis (SFA) is a useful tool to figure out the flow of substance in designated area. SFA is sometimes used to quantify the recycling potentials of the substances. However, few SFA has so far been conducted for rare metals. In this paper, we focused on Dy and conducted SFA of Dy in Japan. The end use of Dy was categorized into 4 groups; automobiles, electronic home appliances, factory automation and voice coil motor, which were further subdivided into 10 categories. We estimated time-series data about the domestic consumption and input of Dy in each end use during 1987-2008 in Japan using bottom-up approach. Stock in-use of Dy was estimated as the recycle potential by using the dynamic SFA, in which the time-series data and lifetime distribution of each end use were used. As a result, the stock in-use of Dy in Japan was estimated as approximately 890-1100 t in 2008. It was also found that, the amount of domestic input (170-220 t) was half of the amount of import (360-400 t) because a lot of Dy contained in final products were exported from Japan.