The Copper Balance of Cities: Exploratory Insights into a European and an Asian City.

Material management faces a dual challenge: on the one hand satisfying large and increasing demands for goods and on the other hand accommodating wastes and emissions in sinks. Hence, the characterization of material flows and stocks is relevant for both improving resource efficiency and environmental protection. This article focuses on the urban scale, a dimension rarely investigated in past metal flow studies.

Sustainable resource use requires "clean cycles" and safe "final sinks".

In order to fulfill the objectives of environmental protection, today's focus on quantitative recycling rates must be amended by a more qualitative approach. Because modern products represent a mix of numerous and sometimes hazardous substances, ways must be explored to remove detrimental substances during recycling and to establish "clean cycles". On the one hand, such a "clean cycle" strategy will result in better recycling qualities of secondary products and less dissipation of hazardous substances during further product use.