WEST LAFAYETTE, Indiana -- A Purdue University professor has created a process to turn toxic coal ash into metals used in the production of cell phones, medical scanners, missile controls and other technology.
If the process succeeds on a large scale, it could make the United States competitive in the $4 billion-a-year rare earth element production market currently dominated by China. The market is projected to grow to $20 billion a year by 2024.
Rare earth elements are usually extracted from mineral ores and serve as the vitamins of technology products. The new process extracts REEs from coal ash, the toxic byproduct of burning coal for electricity.
“Once you burn the coal, the REEs are concentrated in the ash,” said Linda Wang, the Maxine Spencer Nichols Professor of Chemical Engineering at Purdue University. “By turning this ash into products, we are solving two problems at the same time – the supply and production of rare earth elements and reducing the risk to the environment.”
Wang said REEs are found in low concentrations in mineral ores. The ores must go through an extensive chemical process to yield high purity metals. The process uses technology from the 1950s and generates a significant amount of environmental waste.
Wang’s technology can extract REE from coal ash in a more environmentally friendly and efficient way. And coal ash is readily available in Indiana, which has an estimated 60 million cubic yards of coal ash – more than any other state. The ash is stored in ponds and landfills and can threaten the water supply and potentially cause other environmental health problems.
The U.S. led the world’s supply of REE from 1960-1980, but China now controls 90 percent of the supply due to cheaper labor and less strict environmental rules.
“It’s all about supply and demand,” said Keith Belton, director of the Manufacturing Policy Initiative at the Indiana University School of Public and Environmental Affairs. “China has a supply and they’ve set up processing capabilities which can be very dirty and expensive in other countries, so that’s where everybody gets their supply.”
Wang said Chinese manufacturers dump the waste from REE extraction without treating it and without taking measures to protect the environment. NASA images from 2001 and 2006 of China’s Bayan Obo mine, which has the world’s largest REE deposit, show growing “tailings” or waste from REE production.
Wang cautions that in less than 20 years, China could control the production of all high- tech products because it also controls the REE market.
“This is very concerning because we can’t produce a lot of products domestically,” she said. “That’s why I’m motivated to change that.”
The U.S. dependency on China for rare earth elements also is seen as a potential risk to national security.
“It’s always a risk with China because they are essentially a planned economy and they can just cut off supply of materials if the government decides they want to do that to the world, but China also makes a lot of money off rare earth metals,” Belton said. “It’s not always in their interest to just stop exporting materials that people want to buy.”
However, Belton said, “It’s good from a defense perspective to have a U.S. supply separate from strategic competitors such as China.”
In September the Department of Defense released a report on strengthening the manufacturing and supply chain of the US from a national security perspective. Dependency on China as a sole supplier for REE was listed as a risk.
“China is the single or sole supplier for a number of specialty chemicals used in munitions and missiles,” the report said. “In many cases, there is no other source or drop-in replacement material and even in cases where that option exists, the time and cost to test and qualify the new material can be prohibitive – especially for larger systems (hundreds of millions of dollars each).”
The U.S. has one rare earth mine in Mountain Pass, California, which was sold in 2017 to an American-led consortium with Chinese mining company Leshan Shenghe Rare Earth Co. The Canadian-led company UCore Rare Metals also has plans to explore REE mining in Ketchikan, Alaska.
Besides REE, Wang has been able to extract three other products from coal ash: high purity sodium silicate, which can be used for purifying beer and sorbents; aluminum oxide, which can be further reduced to aluminum; and iron oxide, which can be reduced to iron.
“We have so much coal ash in this country that we don’t need to import any materials for aluminum,” Wang said.
Processing coal ash into products will also create jobs, Wang said.
“This will also set a good example to the rest of the U.S. and the world that we can do something about this coal ash,” she said. “We can turn this waste into useful products. I think that’s a good thing for the environment and also for the economy.”