MANY plans for reducing the world’s emissions of carbon dioxide—at least, those plans formulated by environmentalists who are not of the hair-shirt, back-to-the-caves persuasion—involve peppering the landscape with wind turbines and replacing petrol-guzzling vehicles with electric ones charged up using energy gathered from renewable resources. The hope is that the level of CO2 in the atmosphere can thus be kept below what is widely agreed to be the upper limit for a tolerable level of global warming, 450 parts per million.
Wind turbines and electric vehicles, however, both rely on dysprosium and neodymium to make the magnets that are essential to their generators and motors. These two elements, part of a group called the rare-earth metals, have unusual configurations of electrons orbiting their nuclei, and thus unusually powerful magnetic properties. Finding substitutes would be hard. Motors or generators whose magnets were made of other materials would be heavier, less efficient or both.