Defining regional recycling indicators for metals

Recycling indicators are useful for characterizing anthropogenic metal cycles. While there are suitable and generally accepted recycling indicators at the global level, they are not necessarily useful for regional cycles (where the region of interest can be a part of country, an entire country or a group of countries), which are open and interact with other regions such that cross-border flows need to be considered. Herein, we theoretically examine the applicability of available (global) recycling indicators to the regional level and, in the case of the recycling input rate (RIR) and the recycled content (RC), propose modified versions that are both conceptually compatible with the corresponding global indicators and readily accessible through data collected and estimates generated in regional material flow analysis work. The practicability and usefulness of the proposed set of indicators is explored by using published aluminum cycles for the USA (RIR = 44%, RC = 40%), China (RIR = 18%, RC = 18%) and Austria (RIR = 100%, RC = 73%) and compared to the global (RIR = 31%, RC = 31%) aluminum cycle.