Metal stocks in society
“Urgent action is now clearly needed to sustainably manage the supplies and flows of these specialty metals given their crucial role in the future health, penetration and competitiveness of a modern high-tech, resource efficient Green Economy”.
Achim Steiner, UN Under-Secretary General and UNEP Executive Director
A key question that relates to the very broad and intensive use of metals is whether society needs to be concerned about long-term supplies of any or many of them. This is a many-faceted question that cannot be answered quickly or unequivocally.
To address it, the International Resource Panel’s Working Group on Global Metal Flows envisions a series of six reports, of which this is the first one addressing metal stocks in society.
The continued increase in the use of metals over the twentieth century has led to a substantial shift from geological resource base to metal stocks in society. This report reviews the relevant literature on this topic. From a compilation of 54 studies, it is clear that a reasonably detailed picture of in-use stocks and in-use lifetimes exists for only five metals: aluminum, copper, iron, lead, and zinc. Limited data suggest that per capita in-use stocks in more developed countries typically exceed those in less-developed countries by factors of five to ten. Reliable data on metals stocks in society and their lifetimes are essential for building a global recycling infrastructure in the future.
Geological Metal Stocks
Reserve base estimates of the US Geological Survey and other geological sources provide a lower limit to the extractable global resource (EGR, the amount of a given metal in ore that is judged to be extractable over the long term). However, reserve base estimates are lacking for many metals of interest, though approximations are sometimes possible.
For a rough upper limit, elemental abundance ratios in the upper continental crust can be used to estimate EGR (although these are unrealistically high estimates, because much of this material is unsuitable for mining). These upper and lower limit end points are judged to be too wide to be useful in arriving at central estimates. As a consequence, generating best estimate EGR numbers across the elements of the periodic table remains a work in progress. However, it is possible to use new approximations for EGR from the present work together with existing Reserve Base and Reserves information to provide rough Reserve Base and Reserve estimates for elements where those metrics have not previously been reported.
These numbers are presented as working values that can be used in preliminary studies of long-term metal criticality until more authoritative estimates become available.
Download the report Estimating Long-Run Geological Stocks of Metals