CNN —

Millions of tons of coal ash left over from burning the planet’s dirtiest fossil fuel are sitting in ponds and landfills, able to leach into waterways and pollute soil. But this toxic waste may also be a treasure trove for the rare earth elements needed to propel the world toward clean energy.

Scientists analyzed coal ash from power plants across the United States and found it could contain up to 11 million tons of rare earth elements — nearly eight times the amount the US has in domestic reserves — worth around $8.4 billion, according to recent research led by the University of Texas at Austin.

It offers a huge potential source of domestic rare earth elements without the need for new mining, said Bridget Scanlon, a study author and research professor at UT’s Jackson School of Geosciences. “This really exemplifies the ‘trash to treasure’ mantra,” she said. “We’re basically trying to close the cycle and use waste and recover resources in the waste.”

These so-called rare earths are a cluster of metallic elements, with names like scandium, neodymium and yttrium, which exist in the Earth’s core. They have a critical role in clean technology, including electric vehicles, solar panels and wind turbines.

Despite their name, these metals are not rare in nature, but can be hard to extract and separate from the ore that surrounds them such that demand is outpacing supply.

As the world moves away from planet-heating fossil fuels, more rare earths will be needed. Demand for the metals is expected to soar up to seven times current levels by 2040, according to the International Energy Agency.

Yet US supply remains small. Its only large scale rare earths mine is Mountain Pass in California. The country currently imports more than 95% of its rare earth elements, the vast majority of which come from China, posing supply chain and security issues.

“We need to improve the situation,” Scanlon told CNN. That’s why there has been a move to look at unconventional sources of rare earths, she said, “and one of these sources is coal and coal byproducts.”

Coal ash contains relatively low concentrations of rare earth elements compared to what can be mined directly from underground deposits. The advantage is that it’s readily available. Around 70 million tons of coal ash is produced each year in the US.

“There’s huge volumes of this stuff all over the country. And the upfront process of extracting… is already taken care of for us,” said Davin Bagdonas, a study co-author and research scientist at the University of Wyoming.

The aftermath of the collapse of a coal ash pond at the TVA Kingston Fossil Plant in Harriman, Tennessee, on December 22, 2008. Wade Payne/AP

The Dallman coal ash pond in Springfield, Illinois, in November 2021. Justin L. Fowler/The State Journal-Register/USA Today Network/Imagn Images

Where the coal is from determines how straightforward rare earth extraction would be, the study found.

Coal ash from the Appalachian Basin contains the highest amounts of rare earth elements, but only 30% can be extracted. Coal ash from the Powder River Basin, which straddles Wyoming and Montana, has the lowest average concentration of elements but more than 70% can be extracted.

The extraction process from coal ash could be costly, said Paul Ziemkiewicz, director of the Water Research Institute at West Virginia University, who was not involved in the study. The costs of mining need to be weighed against how much product can be recovered, he told CNN.

“Strong acids and bases are needed to extract rare earth elements. Both are expensive,” Ziemkiewicz said. Coal ash from the West can contain higher concentrations of alkaline minerals, he added, which would increase costs as alkalinity neutralizes the acid.

The more chemicals required for the process, the higher the potential environmental impacts.

Rare earth elements also only make up a tiny proportion of coal ash, Ziemkiewicz added, so their extraction “wouldn’t change the volume requiring disposal and storage.” Coal ash contains contaminants like mercury, arsenic and lead, making it a very risky waste stream.

The study authors, however, suggest the value from extracting rare earth metals could be used to offset the costs of improving the way coal ash is stored and managed.

In April, the Biden administration announced a $17.5 million investment into projects to extract rare earths from coal and its waste.

The funding “will increase our national security while helping rebuild America’s manufacturing sector and revitalize energy and mining communities across the country,” Energy Secretary Jennifer Granholm said in a statement at the time.

Some have expressed concerns that transforming coal ash into something valuable could be used to push for more coal, the dirtiest of the planet-heating fossil fuels.

It’s not something Scanlon is too concerned about. “We will be using legacy waste for the most part,” Scalon said. There are currently more than 2 billion tons of coal ash stored across the US, according to the Department of Energy. “There is no indication that future reliance upon coal ash as a feedstock for critical materials will incentivize coal power,” said a DOE spokesperson.

The broader aim is to find out ways to get a range of products from coal in addition to rare earths, Scanlon said, to extract value from it without burning it.

Over the fields of Oklahoma, a little-known, toxic, organic pollutant has been reported for the first time. Its impacts are currently unknown, but researchers believe it’s something that governmental agencies should keep a close eye on.

Chemists at the University of Colorado Boulder were recently toying around with high-tech instruments in Oklahoma with the hopes of learning about how aerosol particles form and grow in the atmosphere. Unexpectedly, they noticed the presence of medium-chain chlorinated paraffins (MCCPs) in the atmosphere.

These awkwardly named substances are used in fluids for metalworking and the manufacturing of PVC and textiles. They have a tendency to trickle into wastewater and eventually end up in biosolids, processed human sewage sludge used as fertilizer. The biosolids are then sprinkled on agricultural fields, which is thought to be the source of this pollution in the atmosphere.

“When sewage sludges are spread across the fields, those toxic compounds could be released into the air. We can’t show directly that that’s happening, but we think it’s a reasonable way that they could be winding up in the air. Sewage sludge fertilizers have been shown to release similar compounds,” Daniel Katz, lead author of the study and PhD student at CU Boulder, said in a statement.

MCCPs have been reported in the atmosphere of Asia and Antarctica before, but it’s the first time they’ve been officially logged in North America, or the Western Hemisphere in general. Since it is early days, their precise impact on human health and natural ecosystems is not fully understood. However, preliminary research suggests they have the potential to cause real harm, and environmental health groups are already calling for them to be banned.

Their close relatives, short-chain chlorinated paraffins (SCCPs), are regulated by the US Environmental Protection Agency and the Stockholm Convention, a global treaty to control persistent organic pollutants. The regulation of MCCPs is currently under consideration by the Stockholm Convention.

In a slightly ironic twist, the tight regulation of SCCPs may have actually increased the production of the newfound MCCPs.

“We always have these unintended consequences of regulation, where you regulate something, and then there’s still a need for the products that those were in, so they get replaced by something, explained Ellie Browne, CU Boulder chemistry professor and co-author of the study.

With that in mind, the researchers say their findings suggest that authorities should start looking into levels of MCCPs in the atmosphere and evaluating the risks.

“We identified them, but we still don’t know exactly what they do when they are in the atmosphere, and they need to be investigated further. I think it’s important that we continue to have governmental agencies that are capable of evaluating the science and regulating these chemicals as necessary for public health and safety,” Katz said.

The study is published in the journal ACS Environmental Au.

Far beyond the eight familiar planets in our solar system, countless bizarre and extreme worlds await discovery — and some have already been found.

Thanks to rapidly advancing telescope technology, astronomers have detected more than 5,600 planets outside our solar system. These exoplanets , as scientists call them, are worlds of lava, and worlds of water. They’re worlds being ravaged by the heat of their stars, and worlds locked in eternal night. There are worlds that look like they were stolen straight from “Star Wars,” and worlds that may hold exotic forms of life never dreamed up in science fiction.

Join us as we tour some of the strangest and most fascinating exoplanets in our ever-surprising universe.

The “hell planet” where it rains lava

(Image credit: NASA/JPL-Caltech)

55 Cancri e is a rocky world about eight times the size of Earth, making it a type of exoplanet known as a “super Earth.” Despite its ample size, nothing is “super” about the living conditions here. Often nicknamed the “hell planet,” 55 Cancri e is completely covered in flowing seas of lava, and it may even rain lava there as well. The exoplanet is located 41 light-years from Earth, making it a popular target for studies (but not for summer getaways).

Related: 38 jaw-dropping James Webb Space Telescope images

The water world with (potentially) living oceans

(Image credit: NASA, ESA, CSA, Joseph Olmsted (STScI))

K2-18 b is a large world located about 120 light-years from the sun. It inhabits the “Goldilocks zone” around its star, meaning that liquid water (and potentially life) could exist there. A recent analysis with the James Webb Space Telescope (JWST) supports the idea that the exoplanet may have its own liquid water ocean — and that the ocean may be home to living creatures . In the study, JWST detected possible traces of dimethyl sulfide, a chemical known to be emitted only by phytoplankton on Earth, in the exoplanet’s atmosphere.

The real-world “Tatooine”

(Image credit: NASA/JPL-Caltech)

Luke Skywalker would feel right at home on Kepler-16b . This exoplanet is the first known circumbinary planet — a planet that orbits two stars at the same time, just like Tatooine from the Star Wars franchise. However, because this huge planet has a gassy surface similar to Saturn’s, even a Jedi would have a hard time finding their footing on this exoplanet, which is located about 200 light-years from the sun.

The rule-breaking behemoth

(Image credit: Penn State)

The giant exoplanet LHS 3154b has scientists scratching their heads, because it seems far too large for its tiny star. This planet, which is about 13 times more massive than Earth but orbits a star nine times less massive than the sun, doesn’t seem like it could exist, researchers said upon its discovery in 2023. Future studies of this “impossible” world could upend the known rules of planet formation.

The largest exoplanet in the known universe?

(Image credit: NASA/JPL-Caltech)

With twice the radius of Jupiter, the exoplanet HAT-P-67 b may be the largest known planet in the universe , in terms of width. But despite its monumental girth, there are more massive worlds out there. This honkin’ world, located about 1,200 light-years from Earth, has a very low density, giving it only about one-third the mass of Jupiter.

The “fluffy” planet where it rains sand

(Image credit: Illustration: LUCA School of Arts, Belgium/ Klaas Verpoest (visuals), Johan Van Looveren (typography). Science: Achrène Dyrek (CEA and Université Paris Cité, France), Michiel Min (SRON, the Netherlands), Leen Decin (KU Leuven, Belgium) / European MIRI EXO GTO team / ESA / NASA)

Located 200 light-years from Earth, the exoplanet WASP-107b also has a very low density, making it appear “fluffy” in telescope observations. A recent JWST study of the planet revealed clouds potentially made of fine-grained silicate particles, meaning it may literally rain sand on this puffed-up world.

The “eyeball planet” with potentially living seas

(Image credit: BENOIT GOUGEON, UNIVERSITÉ DE MONTRÉAL)

Sitting just 50 light-years from Earth, the beady-eyed exoplanet LHS 1140 b may be a candidate for alien life thanks to its one-of-a-kind surface. Scientists studying the world with JWST found that the planet may be covered in ice — except for the one part of its surface that permanently points toward its host star. Here, the star’s heat may melt just enough ice for a circular, liquid water ocean to form, according to the researchers. Besides giving the planet a distinct bull’s-eye appearance, this rare ocean may be a prime place for extraterrestrial life to flourish, the team wrote.

The rotten-egg world

(Image credit: Roberto Molar Candanosa/Johns Hopkins Univeristy)

The exoplanet HD 189733 b , located about 64 light-years from Earth, has a chemical composition so distinct that astronomers can practically smell it from across the galaxy. A recent JWST study of the planet found that its atmosphere contains significant amounts of hydrogen sulfide — a toxic and flammable gas given off by decaying organic matter and volcanoes on Earth — which smells like rotten eggs. The smelly egg planet is far too hot for life to exist (thank goodness), but the mere fact that scientists can detect such distinct molecules in its atmosphere is a good sign that JWST may soon be able to detect signatures of life elsewhere in the universe.

The “Vulcan planet” that may not exist

(Image credit: NASA/Robert Lea (created with Canva))

In a remarkable case of science fiction reflected in reality, scientists have reported the discovery of a planet similar to Vulcan, the home world of Dr. Spock in the Star Trek franchise. The planet was discovered in 2018 around the real star 40 Eridani A — the very same star that hosts Spock’s home planet in the famous sci-fi series. However, recent follow-up observations of the star have called the planet’s existence into question; subtle wobbles in the star’s light signature may result not from a nearby planet’s tugging on it but rather from regular eruptions on the star’s surface. The existence of the Vulcan planet, named HD 26965 b, now seems in doubt.

The Earth-like planet around a small, red star

(Image credit: Robert Lea (created with Canva))

Earth may have a long-lost twin in a nearby star system. Named Gliese 12 b , the planet orbits a hot, red star in a system roughly 40 light-years from Earth. Remarkably, the exoplanet appears to have a width 1.1 times that of Earth, giving it similar properties to our own planet. And while Gliese 12 b orbits its home star much more closely than our planet does the sun (one year there lasts about 13 Earth days), that star is also much smaller, keeping the planet in the habitable zone where liquid water can form on the planet’s surface. That means our distant twin may even have its own version of life.

The Earth-size planet with eternal night

(Image credit: Lionel Garcia)

Not all Earth-size planets are lucky enough to be habitable. Take SPECULOOS-3 b, a rocky, Earth-like world whose orbit around its red dwarf star is a little too close for comfort. Completing an orbit every 17 hours, the rocky world is exposed to so much radiation that its atmosphere was likely blasted away long ago, leaving the unlucky planet totally barren. The roasting temperatures aren’t a global phenomenon, however; this planet is tidally locked, meaning one side always faces its star in eternal day, while the other side sits in perpetual night.

The red volcano world that’s “melting from within”

(Image credit: NASA, ESA, CSA, Dani Player)

Astronomers have discovered a planet in a distant star system that appears to be erupting with so many volcanoes, the world literally glows red when seen through telescopes. The smoldering exoplanet, named TOI-6713.01 , is located roughly 66 light-years from Earth and orbits its star closely, completing a loop every 2.2 Earth days. Observations suggest the planet is covered in molten lava, released by hundreds of active volcanoes. The planet is also subject to incredible internal friction from the gravity of its star and its neighboring planets, which may be causing the world to literally melt from within.

The gas giant with bullet-like wind

(Image credit: NASA, ESA, CSA, Ralf Crawford (STScI))

Scientists have mapped the weather on an enormous exoplanet 280 light-years from Earth, and the forecast looks grim. The planet, named WASP-43b , is tidally locked, with one massive face always pointing toward its star and the other cloaked in eternal darkness. Significant temperature differences between the two sides drive fierce winds, which scientists estimated to blow at up to 5,600 mph (9,000 km/h) — several times faster than a speeding bullet.

The hellish world with glorious rainbows

(Image credit: ESA)

The exoplanet WASP-76 b — located about 637 light-years from Earth — is not the type of place you’d want to vacation. Orbiting 20 times closer to its home star than Mercury orbits the sun, the planet’s dayside is estimated to reach 4,350 degrees Fahrenheit (2,400 degrees Celsius), making it a true hell world. There is one draw, however: A strange bright spot observed on the planet’s surface, right where the day and night sides meet, could be a “glory” — a rare visual phenomenon, sometimes seen on Earth, made up of concentric rainbow rings forming a giant circle.

The giant planets orbiting dead stars

(Image credit: Robert Lea (created with Canva))

One day, the sun will die — but some planets in our solar system may live on. Scientists made this inference after discovering two enormous planets orbiting “dead” white dwarf stars in distant star systems. Named WD 1202-232 and WD 2105-82 , the planets are estimated to be between one and seven times as massive as Jupiter, and both orbit small, dead stars at distances of at least 11.5 times that between Earth and the sun. Their discovery, if confirmed, hints that our solar system’s comparable planets, Jupiter and Saturn, may be able to survive the inevitable death of the sun one day. (Earth, sadly, is likely to be swallowed up during our star’s final expansion.)

The “rogue” planets of Orion

(Image credit: NASA, ESA, CSA / Science leads and image processing: M. McCaughrean, S. Pearson, CC BY-SA 3.0 IGO)

Most known planets orbit stars, but there may be countless others that don’t. Scientists using the JWST have discovered hundreds of free-floating “rogue planets” zooming through the Orion Nebula, untethered to any star. Strangely, about 80 of these rogue worlds are trapped in binary orbits with each other, tumbling through space in pairs. Scientists are not certain how these worlds got ejected from their home star systems or why they are trapped in binary orbits. Given that these planets are roughly as massive as Jupiter, scientists have dubbed them Jupiter-mass binary objects — or JuMBOs, for short.

The distant planet we can actually see

(Image credit: ESO)

Scientists detect most exoplanets indirectly, by watching changes in the light emitted by distant stars. But in 2004, researchers got direct visual confirmation of an alien world for the first time ever. Called 2M1207b, the exoplanet is located about 170 light-years away, in the constellation Centaurus, and is a gas giant about five times more massive than Jupiter. The team spotted the distant world by looking at it in three different infrared wave bands, which helped reveal the planet’s heat while blocking the light of its home star. Since this groundbreaking discovery, roughly 200 exoplanets have been discovered through direct imaging, while more than 5,000 others have been revealed through other means.

The planet with clouds of quartz

(Image credit: NASA, ESA, CSA, and R. Crawford (STScI))

Can you imagine a sunset filtered through a crystal sky? That may be a reality on the exoplanet WASP-17b , a Jupiter-like gas giant that’s so hot that its clouds are made of quartz crystals, observations with JWST suggest. The planet orbits extremely close to its home star, giving it an atmosphere with temperatures reaching a blistering 2,700 F (1,500 C). This heat forms tiny, sand-size silica particles in the planet’s atmosphere, which may coalesce into clouds of pure quartz, researchers suggest.

The baby Jupiter about to be born

(Image credit: ESO/ALMA (ESO/NAOJ/NRAO)/Weber et al.)

Exoplanet-hunting scientists zoom in on not just existing worlds but also worlds that are about to be born . While studying the region around the star V960 Mon, located about 5,000 light-years from Earth, scientists spotted a clumpy field of gas where two tendrils of material are apparently being funneled into distinct, planet-like lumps. According to the researchers, who made the discovery using the European Southern Observatory’s Very Large Telescope and the Atacama Large Millimeter/submillimeter Array, this is the first time scientists have imaged a young star system on the verge of birthing its first giant planets.

The sibling planets dancing in lockstep

(Image credit: ALMA (ESO/NAOJ/NRAO)/Balsalobre-Ruza et al.)

Around the distant star PDS 70, located 370 light-years from Earth, resides an incredibly rare pair of sibling planets . One fully formed world roughly the size of Jupiter appears to swirl around its host star; behind it, in the same orbit, is an enormous cloud of gas and dust that researchers suspect may be the planet’s partially formed sibling. Although only one of the objects seems to be a full-fledged planet, the pair is the first evidence of rare “Trojan planets” — two worlds that formed at nearly the same time, in roughly the same place around their home star, moving in the exact same orbit.

The planet turning its star into a “spiral galaxy”

(Image credit: ESO)

About 500 million light-years from Earth is a star system that looks suspiciously familiar. Wrapped in two dusty spiral arms , it resembles our own Milky Way galaxy — although on a much, much smaller scale. The reason for this star’s galactic appearance? Astronomers suspect it’s because of a hidden, Jupiter-size planet dubbed MWC 758 c, which used its massive gravitational pull to sculpt the star’s sheath of dust into spectacular spiral arms. The planet has yet to be fully confirmed, but simulations show it’s a likely cause of its home star’s odd look.

The mirror world that shouldn’t exist

(Image credit: ESA/Cheops)

Most planets reflect at least a bit of their home star’s light. But the exoplanet LTT9779 b reflects a whopping 80% of its star’s incoming rays — the highest reflectiveness of any planet ever discovered. The key to the planet’s impressive albedo is a layer of metallic clouds that surrounds it. Scientists suspect the Neptune-size world’s sky is mostly full of silicate, or glass, and titanate, a salt containing titanium — turning the planet’s atmosphere into a veritable mirror. The planet’s existence poses a puzzle for scientists: The world orbits so closely to its star that its atmosphere should have been blown away by now. The key to its survival may be the metal in the planet’s skies, which may be too heavy for solar wind to blast it away.

The “zombie” planet that survived its star’s death

(Image credit: W. M. Keck Observatory/Adam Makarenko)

The exoplanet 8 Ursae Minoris b , also known as Halla, is a hot, Jupiter-like world located 520 light-years from Earth. Observations suggest the massive world should have been completely incinerated by its home star, which has already entered its red giant phase and appears to have long since ballooned outward into its system, scorching everything in its path, before shrinking back to its current size. The fact that Halla orbits relatively close to the star suggests it was either born after the star shrank again or the star that’s visible today is one of two binary stars that merged, preventing either one from expanding on its path of destruction.

The water world with a steam atmosphere

(Image credit: NASA/JPL-Caltech/R. Hurt (IPAC))

The exoplanet GJ 1214b is located just 40 light-years from Earth, but it’s coated in so many thick clouds that scientists had a hard time studying it until recently. Using JWST’s infrared vision to peer through the clouds, scientists analyzed the planet and saw what appeared to be an atmosphere made of steam, suggesting the world below may contain significant amounts of water.

The Earth-like planet with no atmosphere

(Image credit: NASA, ESA, CSA, J. Olmsted (STScI))

Around the distant star TRAPPIST-1, seven rocky, Earth-size planets swirl through the star’s habitable zone. Whether any of these planets contain the right conditions for life is a question astronomers are eagerly investigating. But one of them, TRAPPIST-1b , may be officially out of the running. JWST’s observations of the rocky, Earth-like world reveal that the planet is about as hot as an oven — a whopping 450 F (232 C) — and almost certainly doesn’t have an atmosphere. Some of the scorching world’s neighbors may be better positioned for life to emerge, but more research is needed to know for sure.

The extraterrestrial sandstorm planet

(Image credit: NASA, ESA, CSA, Joseph Olmsted (STScI))

Scientists using JWST have spotted a gargantuan sandstorm raging on the exoplanet VHS 1256 b , located roughly 40 light-years from Earth. An enormous world that’s far from its star, the “super-Jupiter” takes about 10,000 years to complete a single orbit. That large distance means scientists can see the planet’s atmosphere relatively clearly, without too much starlight getting in the way. Recent observations showed incredibly hot clouds made of silicate particles swirling through the planet’s atmosphere. According to the researchers, this may be evidence of a gargantuan dust storm.

The planet hotter than a star

(Image credit: NASA/JPL-Caltech)

KELT-9b is an extremely hot, Jupiter-like planet located 670 light-years from Earth. With an estimated surface temperature of 7,800 F (4,300 C), it was deemed the hottest exoplanet ever discovered upon its detection and is even hotter than some stars. This intense heat has a nasty impact on the planet’s atmosphere: On KELT-9b’s dayside, the heat of the nearby star beats down so intensely that hydrogen molecules in KELT-9b’s atmosphere are literally ripped to shreds and blown across the planet. With one-half of the planet’s atmosphere constantly melting, this world is one extraterrestrial destination you’d definitely want to avoid.

(Image credit: NASA, ESA, and J. Olmsted (STScI))

Located about 900 light-years from Earth, the exoplanet WASP-121b is so hot that heavy metals are constantly boiling through its atmosphere and venting into space. Scientists spotted iron and magnesium molecules so high above the planet’s surface that they could escape the pull of gravity and drift away. The extreme heat comes from the planet’s ultraclose proximity to its host star. The planet is so close, in fact, that tidal forces generated by the star’s gravity have stretched the planet into a football shape that distinguishes it from the spherical worlds most often discovered.

The ultrasmall world moving at breakneck speed

(Image credit: NASA)

Located 35 light-years from Earth, L 98-59b is one of the smallest exoplanets ever discovered, with a mass just 0.4 times that of Earth. The tiny world also rockets around its home star at breakneck speed, completing an orbit in just two days, six hours. Because of this, the planet receives roughly 22 times as much energy from its home star as Earth does from the sun, almost certainly rendering the tiny, fast-moving planet uninhabitable.

Earth’s “older cousin”

(Image credit: NASA)

The exoplanet Kepler-452 b appears so similar to our home planet that NASA has dubbed the world “Earth’s older cousin.” The rocky exoplanet orbits a sunlike star at virtually the same distance that our planet orbits the sun, with a year there lasting about 384 days. That puts the planet firmly in the habitable zone, where liquid water could form on its surface. Sadly, our cousin will remain estranged for a good while longer: At nearly 1,800 light-years from Earth, the planet would take at least 30 million years to reach by spacecraft.

The bizarrely close sibling planets

(Image credit: NASA)

The exoplanet Kepler-36b is a rocky world that’s about 1.5 times the size of Earth and orbits bizarrely close to its neighboring world, the Neptune-like exoplanet Kepler-36c. The two alien worlds make extremely close approaches to each other every 97 days, on average; during those cosmic family reunions, the two planets are separated by less than five Earth-moon distances. These ultraclose encounters exert tremendous tidal forces on the sibling planets, possibly promoting active volcanism on the rocky Kepler-36b.

The unlucky planet around a toddler star

(Image credit: NASA, ESA, Joseph Olmsted (STScI))