Material stocks and flows accounting for copper and copper-based alloys in Japan

Abstract

The recovery of scrap metal for recycling contributes to the conservation of natural resources and the construction of a sound material-cycle economy. Dynamic material flow analysis (MFA) allows us to investigate the potential for scrap metal recovery in a given region. This paper performs a dynamic material stock and flow analysis of copper in Japan. Previous studies paid little attention to the grade of the materials; the present paper considers the division between high-purity copper and copper alloys. The paper applies a dynamic MFA model with greater detail than many earlier studies and demonstrates an additional level of disaggregated analysis on waste flows. The analysis of differing grades of copper quantified the flow of downgraded scrap from the pure copper cycle to the copper alloy cycle. In addition, the amount of scrap collected, as estimated by the dynamic MFA, was approximately consistent with that reported in the statistics. This result indicated the validity of the parameters used in the dynamic model. The current in-use copper stock in Japan was estimated to be 18.7 Tg including the mass of alloying elements, and the amount of cumulative uncollected copper was estimated to be 9.9 Tg. This uncollected copper could have been mixed with other metals (e.g., mixed in secondary steels), incinerated with combustible waste, landfilled, or exported in several forms. The amounts of copper to these final destinations were quantified. Finally, the Japanese pure-copper cycle and copper alloy cycle for 2005 were constructed.