Dynamic analysis of in-use copper stocks by the final product and end-use sector in Japan with implication for future demand forecasts

Abstract

Analysis of in-use metal stocks provides information on the potential quantity and quality of the generated waste and secondary metals and an understanding of metal demands. Previous studies have analyzed the in-use metal stocks mainly considering their volume and final products. However, an end-use sector where a final product is used (e.g., household, industry) is essential for information on the waste origin and recycling route. Therefore, in this study, the historical trends of in-use stocks and waste flows of copper in Japan until 2015 are comprehensively identified with high resolution of both the final products and end-use sectors based on input-output and dynamic material flow analysis. The results show that in-use copper stocks in manufacturing, infrastructure-related sectors, and household already peaked and decreased until 2015, while those in real estate and residence continued to increase. The in-use total copper stock peaked in 2008 (22.5 Tg) and later decreased, with 21.1 Tg in 2015, while the total copper waste flows increased, resulting in 1.0 Tg in 2015. Our analysis of copper waste flows indicates that the household was a significant end-use sector for copper recycling with unrecycled copper flows of 60.6 Gg in 2015. Furthermore, our analysis suggests that the Japanese in-use copper stocks per capita for some end-use sectors decreased as per capita GDP increased, and some country-specific factors affected the in-use copper stock growth. The findings will help future demand forecasts and develop resource policies and recycling strategies toward sustainable metal management.