As
the world moves toward greater use of low-carbon and zero-carbon energy
sources, a possible bottleneck looms, according to a new Massachusetts
Institute of Technology (MIT) study: The supply of certain metals needed for key
clean-energy technologies.
Wind
turbines, one of the fastest-growing sources of emissions-free electricity,
rely on magnets that use the rare earth element neodymium. And the element
dysprosium is an essential ingredient in some electric vehicles’ motors. The
supply of both elements—currently imported almost exclusively from China—could
face significant shortages in coming years, the research found.
The
study, led by a team of researchers at MIT’s Materials Systems Laboratory—postdoctoral
researcher Elisa Alonso PhD ’10, research scientist Richard Roth PhD ’92,
senior research scientist Frank R. Field PhD ’85, and principal research scientist
Randolph Kirchain PhD ’99—has been published online in Environmental Science
& Technology. Three researchers from Ford Motor Company are coauthors.
The
study looked at 10 so-called rare earth metals, a group of 17 elements that
have similar properties and which—despite their name—are not particularly rare
at all. All 10 elements studied have some uses in high-tech equipment, in many
cases in technology related to low-carbon energy. Of those 10, two are likely
to face serious supply challenges in the coming years.
The
biggest challenge is likely to be for dysprosium: Demand could increase by
2,600% over the next 25 years, according to the study. Neodymium demand could
increase by as much as 700%. Both materials have exceptional magnetic
properties that make them especially well suited to use in highly efficient,
lightweight motors and batteries.
A
single large wind turbine (rated at about 3.5 MW) typically contains 600 kg, or
about 1,300 lbs, of rare earth metals. A conventional car uses a little more
than one pound of rare earth materials—mostly in small motors, such as those
that run the windshield wipers—but an electric car might use nearly 10 times as
much of the material in its lightweight batteries and motors.
Currently,
China
produces 98% of the world’s rare earth metals, making those metals “the most
geographically concentrated of any commercial-scale resource,” Kirchain says.
Historically,
production of these metals has increased by only a few percent each year, with
the greatest spurts reaching about 12% annually. But much higher increases in
production will be needed to meet the expected new demand, the study shows.
China has about 50% of
known reserves of rare earth metals; the United States also has significant
deposits. Mining of these materials in the United States had ceased almost
entirely—mostly because of environmental regulations that have increased the
cost of production—but improved mining methods are making these sources usable
again.
Rare
earth elements are never found in isolation; instead, they’re mixed together in
certain natural ores, and must be separated out through chemical processing. “They’re bundled together in these deposits,” Kirchain says, “and the ratio in
the deposits doesn’t necessarily align with what we would desire” for the
current manufacturing needs.
Neodymium
and dysprosium are not the most widely used rare earth elements, but they are
the ones expected to see the biggest “pinch” in supplies, Alonso explains, due
to projected rapid growth in demand for high-performance permanent magnets.
Kirchain
says that when they talk about a pinch in the supply, that doesn’t necessarily
mean the materials are not available. Rather, it’s a matter of whether the
price goes up to a point where certain uses are no longer economically viable.
The
researchers stress that their study does not mean there will necessarily be a
problem meeting demand, but say that it does mean that it will be important to
investigate and develop new sources of these materials; to improve the
efficiency of their use in devices; to identify substitute materials; or to
develop the infrastructure to recycle the metals once devices reach the end of
their useful life. The purpose of studies such as this one is to identify those
resources for which these developments are most pressing.
While
the raw materials exist in the ground in amounts that could meet many decades
of increased demand, Kirchain says the challenge comes in scaling up supply at
a rate that matches expected increases in demand. Developing a new mine,
including prospecting, siting, permitting, and construction, can take a decade
or more.
“The
bottom line is not that we’re going to ‘run out,'” Kirchain says, “but it’s an
issue on which we need focus, to build the supply base and to improve those
technologies which use and reuse these materials. It needs to be a focus of
research and development.”
