Yale team estimates global rare earth metal flows

Global production of rare earth oxides. Credit: ACS, Du and Graedel. Click to enlarge.

A team at Yale has used published and unpublished information from China, Japan, the United
States, and elsewhere to estimate global flows into use and in-use stocks for 15 rare earth elements (REE): La (Lanthanum); Ce (Cerium); Pr (Praseodymium); Nd (Neodymium); Sm (Samarium); Eu (Europium); Gd (Gadolinium); Tb (Terbium); Dy (Dysprosium); Ho (Holmium); Er (Erbium); Tm (Thulium); Yb (Ytterbium); Lu (Lutetium); and Y (Yttrium).

In a paper published in the ACS journal Environmental Science & Technology, they show that the combined flows into use constituted about 90 Gg (90,000 tonnes) in
2007; the highest for individual metals were ~28 Gg Ce and ~22 Gg La, the
lowest were ~0.16 Gg Tm and ~0.15 Gg Lu. In-use stocks ranged from
144 Gg Ce to 0.2 Gg Tm and summed to 448 Gg total.

The authors, Xiaoyue Du and T. E. Graedel, found that Nd is the second largest in-use stock at 137 Gg. Together, Ce and ND stocks constituted nearly 63% of the total. They also found that 86 Gg La and 50 Gg Pr reside in stocks, as do 8.6 Gg Dy, 6.9 Gg Y, 3.6 Gg Gd, 3.3 Gg Sm, 0.7 Gg
Tb, and 0.4 Gg Eu. These stocks, if efficiently recycled, could provide a
valuable supplement to geological stocks, suggested the authors.

Because of their unique physical and
chemical properties, [rare earth elements] are used in a growing number of
applications and have become indispensible for a number of
critical technologies. For example, scandium is a currently
unmatched ingredient in solid oxide fuel cells and aluminum
alloys, neodymium is vital to high-performance permanent
magnets, and yttrium is a promising raw material for superconductors
and laser technology.

When these intermediate
products are incorporated in final products such as wind
turbines, hybrid electric vehicles, or defense applications, the
rare earths provide performance that is currently irreplaceable
by alternative materials. These and other technical innovations
will strongly influence future demand for rare earths.

—Du and Graedel