They sound like superheroes from a Hollywood science-fiction movie: neodymium, promethium, dysprosium and europium. And the comparison isn't actually all that far fetched, for these elements belong to a group of metals that many scientists--and even more prospectors--believe holds the key to a carbon-free world.
Referred to as rare earth elements, these metals are little known outside the industries that are devouring them, or those who can still remember the periodic table they learned by rote at school. Yet the unique magnetic, conductive and luminescent properties of these 17 metals- 15 lanthanides, along with scandium and yttrium--are underpinning the world's switch to green technology.
Magnets based on rare earth elements are used to make electric motors and generators that are smaller and lighter but as powerful--or more so than those based on iron, and have powered the shift towards hybrid cars. Neodymium is the key component of an alloy used to make the high-power, lightweight magnets for electric motors in the Toyota Prius, Honda Insight and Ford Focus. These magnets preserve their magnetic properties even at high temperatures--something they can also do for the generators incorporated into wind turbines.
Tiny quantities of dysprosium can make magnets in electric motors lighter by 90 per cent, while terbium--which is soft enough to cut with a knife--is a key component of low-energy light bulbs, which use 80 per cent less electricity than traditional incandescent globes. Another rare earth metal, lanthanum, is employed to make the energy-efficient petroleum-cracking catalysts used in modern vehicle engines.
'Rare earths are indispensable,' says Mark Smith, chief executive of Molycorp Minerals, which is mining these elements at Mountain Pass in California. 'The technology is just starting to wake up to the potential for rare earths--their use is growing phenomenally. There are tremendous opportunities, and their application is really only just being understood.'
Green energy may be driving the interest in rare earths, but they are also found in a mind-boggling range of everyday items. Pick a modern device and you'll find rare earths inside, from superconductors, mobile phones and thin-film solar panels to catalytic converters. Virtually all polished-glass products, from ordinary mirrors and eyeglasses to precision lenses, are finished with an oxide of the rare earth cerium, while colour cathode-ray tubes and liquid-crystal displays used in computer monitors and flat-screen televisions employ europium. Lanthanum is key to modifying glass-crystal structure and refraction, stimulating advances in high-tech digital and video cameras.
Miniaturised multi-gigabyte portable disk drives and DVD drives wouldn't exist without magnets made from alloys of rare earths such as neodymium, samarium, praseodymium, dysprosium and gadolinium. Another metal, erbium, possesses optical properties that enable fibre-optic cables to transmit signals over long distances.
Rare earths are also deployed in medical equipment. Lanthanum phosphors in X-ray fihns and lasers reduce radiation doses by three quarters, and the element is also essential to MRI and CAT scans.
Arguably, the use of rare earths has been propelled as much by US Army research as by green technology, and military applications include precision-guided weapons, night-vision goggles and range finders. Yttrium is used in laser crystals specific to military communications, while the notorious 'smart bombs' use neodymium-iron-boron magnets to control direction when dropped from an aircraft.
'We've engineered rare earths into critical aspects of our modern technology,' says Jack Lifton, a consultant and expert on rare earth metals. 'Almost every small electrical motor in our culture--from the hard drive in your computer to the speakers in your Blackberry--contains rare earths.'
NOT SO SCARCE
Despite their name, most rare earth metals are far from rare. The moniker originates from their first discovery, in a so-called rare earth mineral (an uncommon oxide-type mineral) called gadolinite, in an abandoned mine outside the village of Ytterby in Sweden by Karl Arrhenius, a Swedish army lieutenant and amateur mineralogy student, in 1787.
In reality, with the exception of promethium (which has no long-lived isotopes and, according to the US Geological Survey, occurs naturally only in 'vanishingly small' quantities), rare earths are generally found in fairly high concentrations in four minerals--bastnasite, loparite, monazite and xenotime--along with rare-earth ionadsorption clays. The more abundant rare earths are each similar in crustal concentration to commonplace industrial metals such as chromium, nickel, copper, zinc or tin, while cerium is the 25th most abundant element in the Earth's crust.
Rare earth elements are, however, uncommon in one sense: they tend not to become concentrated in exploitable ore deposits. Consequently, most of the world's supply comes from just a few sources. China is currently responsible for 95 per cent of all rare earth production (and has half of the known reserves). China is also responsible for the rise in global production from fewer than 5,000 tonnes in 1955 to around 125,000 tonnes a year in 2008, according to Smith. 'By 2014, the projections are that this will rise to 180,000 tonnes a year,' he says.
However, last year, China said it planned to restrict the amount of rare earths it exports, and to halt export of some elements altogether, in order to conserve reserves. This, combined with the fact that the industrial world has fully taken on board the potential for rare earths, has led to a Klondike-esque scramble for new reserves. 'China's statement sent a shiver through the end-user industry,' says Lifton. 'It has sparked a wave of mining-venture startups, and we're seeing mines being discovered or rediscovered. There have been at least 100 of these in the past 12 months or so.'
Production is being dramatically increased at Molycorp's reopened Mountain Pass mine in California, which closed in 2002, with the quantity of ore retrieved predicted by Smith to jump from 3,000 tonnes this year to 20,000 tonnes in 2012. Other operations are advanced in Canada, Australia and South Africa.
'It's crystal clear that Chinese internal demand is growing so rapidly that if we don't start sourcing alternative sites, then there will be severe shortages within the next couple of years,' says Smith. 'This is an issue that will affect us in the near future--if nothing is done, we will begin to feel the impacts later this year.'
Perhaps the most intriguing opportunity for diversification lies under the exposed, rugged coastal fringes of the Ilimaussaq Intrusion in southwestern Greenland. This year, Greenland gained complete sovereignty over its natural resources, and the government has made it clear that it intends to exploit its numerous mineral belts.
The Ilimaussaq Intrusion is estimated to contain 4.8 million tonnes of rare-earth oxides, which could supply a quarter of the world's rare earths for the next 20 years, along with significant resources of uranium. Commercial operations have been pencilled in for 2013, to be operated by Greenland Minerals, an Australian company that has been exploring the area for the past two years. 'The area is well known to academics for its unusual geological occurrences,' says Dr John Mair, the company's special projects manager. 'It's clear to most people that the area has the potential to expand and become a significant resource of rare earths.'
Pulling rare earths out of the ground is straightforward enough--most are retrieved from opencast mines (although some underground mines are in operation). 'The difficulty is that the ore you pull out contains all the rare earths, so you have to separate them all out,' says Smith. The rare earths are teased out by creating concentrates and then using conventional gravity separation, although this is made more challenging by the fact that the atomic weights of the rare earths are close together.
Yet mining is a dirty business, and critics point to the irony that the metals that drive so many low-carbon products are mined and processed in circumstances that are very polluting. As with other minerals, some of the most environmentally damaging mines are in China: Chinese newspapers--which are usually heavily censored--have been free to report how miners scrape off the topsoil and use acids, ammonias and sulphates to extract rare earths, leading to high sulphate emissions and excessive acid levels in wastewater, along with arsenic-laden waste streams.
'There are clear benefits from the rare earths,' acknowledges Dr Kevin Brigden, senior scientist at the Greenpeace Laboratories at Exeter University. 'But we have to be careful that we're not solving one environmental problem--or simply making life easier for people--but creating another down the line.'
A major risk, according to Brigden, is that a number of rare earths can be found in ores that begin to oxidise when exposed to air, creating acids. 'Once that process starts, it's very difficult to control, even when the mining has stopped,' he says. 'You end up with a lot of acidic mine water, and that can mobilise toxic metals into water courses.'
The stampede to locate and extract rare earths also raises the spectre of rogue outfits operating in the manner of artisan gold miners, according to Brigden. 'When that happened with gold, you ended up with mercury polluting rivers, so we really need to be sure that the checks and balances are in place,' he says.
Others believe that the industry can be trusted to adhere to high standards. 'The Chinese will admit that they need some help with pollution control,' says Lifton. 'But rare earth mining in China is atypical of what happens elsewhere. Standards in the West are exceptionally clean.'
SUPPLY AND DEMAND
Issues over how carefully we mine rare earths and how we use them may soon give way to a greater concern--whether we can keep using them. 'We may already be using them at such a rate that demand is outstripping supply,' says Brigden. 'People haven't really started to address the issue of recycling them. We have recovery programmes to take the gold and platinum out of circuit boards and thelike, but these aren't set up for rare earths.'
And, as global demand soars, supply, even if it is sustained, is likely to follow the market price. 'The defining factor of the next generation will be Asian demand for applications based on rare earth metals,' says Lifton. 'Our lives have been transformed by rare earths, but before long, people in Asia will want Blackberrys and fiat-screen televisions en masse. At some point, we will either not have these materials available in the West, or they'll become expensive.
'We've been guilty in the West of gloriously wasting these metals by not recycling them. We'll have to start thinking soon about just how often we change our cell phones or cars. It's possible that we'll take a step backwards if supply doesn't keep up with demand, and then we'll be going back to tube radios and iron magnets.'…