日本における銅の循環利用ポテンシャルの解析

抄録

  In this paper, recycling potential of copper was analyzed by using a dynamic material flow analysis and a material pinch analysis. In the dynamic material flow analysis, the amount of copper stock in use was quantified as the potential of secondary resources. The amount of stock in use of copper in Japan in 2005 was estimated as 160 kg/cap, which is similar to the result in North America.
  Next, we applied the material pinch analysis to the material flow of copper-based materials in Japan in 2005 to investigate the maximum recycling potential of copper products. The copper-based materials were classified into high-purity copper, brass, bronze and copper-nickel-zinc alloy so that the difference of their chemical compositions could be taken into account. We focused on the concentration of Zn, Sn, Fe, and Pb in copper-based material as indicators of the quality of the materials. Then, the quantity and quality of generated scrap were estimated. We assumed that the copper-based materials were collected without class-by-class separation from the end-of-life products, and the composition of scraps recovered from end-of-life products was calculated as a weighted average of the copper-based materials used in the products. The results of material pinch analysis showed that copper and copper alloy scraps were being recycled in almost optimum way in the current situations of separation and collection.
  Then, scenario analysis was performed by altering the separation technology, collecting rates, in order to quantify the reduction potential of virgin materials inputs in the material flow in Japan. It was predicted that the consumption of virgin materials could be reduced by half if the collecting rate was increased to 100% and each copper-based material was completely separated from end-of-life products.