Global Rare Earth In-Use Stocks in NdFeB Permanent Magnets

TLDR

Rare earth elements are essential for modern technology, especially permanent magnets, yet quantitative data on their use in these magnets are scarce. The study aims to estimate the global in‑use stocks of Pr, Nd, Tb, and Dy in NdFeB permanent magnets. Using historical production data from 1983 to 2007 for China, Japan, the United States, and Europe, the authors calculate these stocks. The estimated stocks are 62.6 Gg Nd, 15.7 Gg Pr, 15.7 Gg Dy, and 3.1 Gg Tb, which, if recycled, could supply almost four times the 2007 annual extraction of each element.

Abstract

The rare earth elements are indispensible in modern technology, especially in the applications of permanent magnets. Very little quantitative information is available on rare earth elements used in permanent magnets, however. This study looks back to 1983, when neodymium-iron-boron (NdFeB) permanent magnets were first manufactured, and reaches to 2007, when the market of permanent magnets was well developed. We draw on the historical data on permanent magnets from China, Japan, the United States, and Europe to provide the first estimates of global in-use stocks for four rare earth elements—praseodymium (Pr), neodymium (Nd), terbium (Tb), and dysprosium (Dy)—in NdFeB permanent magnets. In-use stocks amount to 62.6 gigagrams (Gg) Nd, 15.7 Gg Pr, 15.7 Gg Dy, and 3.1 Gg Tb; these stocks, if efficiently recycled, could provide a valuable supplement to geological stocks as they are almost four times the 2007 annual extraction rate of the individual elements.