Pulling rare-earth elements from deep underground carries the potential for big financial rewards – and big environmental risks.
In China, where 95 percent of all rare earths worldwide are mined, a lack of environmental regulation has allowed massive surface and groundwater pollution.
In Arizona, a state geologist and the head of the University of Arizona’s mining institute say the state should look for rare-earth elements – used in many high-tech gadgets we use every day – but it also must manage the environmental threats.
Exploring for rare-earth minerals has increased in Arizona and New Mexico and across the U.S. to ease our dependence on China. U.S. environmental rules are far stricter than China’s, and experts say the only rare-earth mine in this country operates with great environmental sensitivity – and at great expense.
China’s rare-earth industry each year produces more than five times the waste gas, including deadly fluorine and sulfur dioxide, than the total flared by all miners and oil refiners in the U.S., Bloomberg News has reported.
Plus, rare earth mining there produces 25 million tons of wastewater laced with cancer-causing heavy metals such as cadmium, Bloomberg reported. One reason China has cut production and limited exports of rare earths since 2010 – driving up prices worldwide and triggering interest in exploring for them here – in an effort to reduce pollution.
A single rare-earth mine can produce many elements. That requires numerous steps, each of which can be polluting. For example, it takes more chemicals to separate elements from ore than it does for base metals such as copper, zinc and lead.
“In a typical copper mine you use some degree of chemicals to strip copper out of ore,” said John Kaiser, a mining analyst in the San Francisco area. “With rare earth, you’re literally talking about having a chemical plant to process them.”
Low levels of radioactive thorium and uranium also occur in minerals containing many rare-earth elements. But experts at the UA and New Mexico Tech say those materials can be safely managed.
Rare-earth minerals occur in low concentrations, which means digging up a lot of rock to get enough, said Nicholas Leadbeater, a University of Connecticut chemist who researches green technologies.
While some companies recycle rare-earth wastewater, “if you want a process that generates no waste, extracting rare earths from the ground is not a way to do it,” Leadbeater said.
Processing rare earths is more complicated than for many, more conventional hard rock minerals, said Mary Poulton, a UA professor with mining expertise.
“You’ve got all these elements that have to be separated that are chemically very similar,” said Poulton.
Radioactivity in rare earths can be managed as part of a mine’s design – by containing tailings so they don’t collect water runoff and leave the mine site, Poulton said.
That’s what the one U.S. rare-earth mine in production, in Mountain Pass, Calif., has done. The mine’s operator, Molycorp Inc., invested hundreds of millions of dollars in technologies to recycle wastewater and dramatically reduce tailings when it reopened the 60-year-old site in 2011. That’s why Molycorp had no opposition from the Center for Biological Diversity, which has fought many mines, including Rosemont.
“It’s not that we’re embracing rare-earth mining – it’s a messy, toxic business,” said Brendan Cummings, an attorney for the center. “But rare earths are an important part of a renewable energy economy. There are beneficial uses to the materials if they can be mined in a location and a manner that’s not terribly damaging.”
no Strategy to abate risks
Molycorp’s environmental practices could be a model for future rare-earth mines in Arizona or elsewhere in the Southwest, said Keith Long, a U.S. Geological Survey geologist and mineral economist.
What it’s doing is expensive upfront, but will save on operating expenses down the line, he said. He called Molycorp’s strategy “a ‘no-brainer.'”
In a December 2012 report, the Environmental Protection Agency said that as yet, the agency has no formal strategy for managing and minimizing rare-earth mining’s risks. The EPA said it wants to develop one and noted that the severity of risks varies widely at different operations.
What it comes down to is, “How good are the storage tanks? How good is the containment in the processing building? If you are using various chemicals to process rare earths, how well do you contain them?” said John Hillenbrand, a mining technical expert for EPA’s San Francisco regional office, which covers Arizona.
“How is the mine operated? That seems more important than actual mineral you’re mining.”