Recycling Solutions - Thanatia: The Destiny of the Earth's Mineral Resources - page 433

Panel created by UNEP (Graedel et al., 2011a), recycled content is defined as
the fraction of scrap metal in the total metal input to metal production. The
difference between total metal input and metal production equates to the losses
experienced throughout the entire life cycle. These include residues in mining and
metallurgy derived from tailings, slags, e uents and dust. Also involved are the non-
recycled new scrap residues obtained in the fabrication and manufacturing process
and old scrap recovered from discarded products upon having reached their end-
of-life. Collected metals that suffered downcycling are present too, i.e. old metal
scrap containing trace elements that inhibit functionality. Losses also include all
environmental dissipations at any point of the life-cycle in the form of oxidation,
corrosion, abrasion, coating deterioration, friction, cracking, mixing, etc.
Recycled content as an indicator is absolute in that it measures the actual
amount of metal that enters into the industrial lifecycle of an element. The lifecycle
comprises of mining and metallurgical stages, product manufacture, use, end-of-life
and scrap recycling. Any scrap metal contains both that was generated along the
entire manufacturing chain and that recovered from products that upon reaching
end-of-life were converted into secondary material.
Accordingly, UNEP's International Resource Panel (Graedel et al., 2011a) pre-
sented the global average of recycled content for sixty metals comprising ferrous,
non-ferrous, precious and specialty metals (Fig. 14.1). Perhaps surprisingly, Pb,
Ru and Nb top the list, at more than 50% recycled content. These come before
metals such as Au, Fe and Al which one may normally consider a recycling prior-
ity, particularly given the energy savings associated with secondary aluminium (Al
recycling saves 95% of the energy consumption, Cu 85%, whilst steel and Pb saves
74% and 65%, respectively (Wellmer and Steinbach, 2011)). In contrast, the least
recycled metals at less than 1% recycled content are Li, As, Y , Ba, Os, Tl, Sm,
Eu, Tb, Ho, Er, Tm, Y b and Lu. The International Resource Panel provides no
data about potentially critical elements such as P, K, Sc, Te, Hf, Bi, Th and U.
Similarly, Sibley (2011) showed that in the US only in lead's case, does the
secondary source predominate over new extraction at 60% recycled material and
>90% old scrap recycling e ciency 1 (Fig. 14.2). Titanium, germanium and nickel
have a 50/50 split whilst their recycling e ciency is 90%, 75% and 50-55%, respec-
tively. Any other metal recycling falls below 50%. Tungsten is at 45/55 (60-65%
e ciency); iron and steel, 40/60 (50-55% e ciency); manganese and aluminium
35/65 (50-55% and 38-42% respective e ciency); molybdenum, magnesium, silver,
cobalt, cadmium and copper 30/70 (with respective e ciencies at 29-33%, 38-42%,
>90%, 60-65%, 15% and 38-42%); gold and zinc 27/73 (>90% and 18% respective
e ciency); tin, niobium, tantalum, antimony and chromium 20/80 (with respec-
tive e ciencies for tin, niobium, tantalum, and both antimony and chromium at
1 The recycling e ciency factor provides the percentage of useful metal recovered at the end-of-life
re-entering the metal cycle. Useful here means that the material still retains the physico-chemical
properties that make recycling functional.