Wind Farm Repowering: Profitable Via Tech Improvements and Shows that Partial Asset Stranding Can Be a Net Gain with a Good Payout

 

      According to Iberdrola repowering a wind farm “mainly consists of replacing (partially or totally) the old turbines with more powerful and efficient models using the latest technology. Repowering can multiply the generating capacity of a wind farm and significantly increase electricity production. The reason is simple: each new turbine produces more energy than the old ones and therefore fewer units are needed. According to data from EoLIS 2022, WindEurope's annual event, on average, repowering reduces the number of turbines in a wind farm by a quarter, while increasing the installed capacity of the wind farm by a factor of 2.7 and tripling its electricity production.”

     There are several reasons that repowering wind farms have become more profitable including technology and efficiency improvements, turbine size increases, more output per turbine, inefficiency of older wind farms with low-tech turbines deployed in the best wind conditions, electricity demand and prices, and regulatory incentives.

     The benefits of repowering wind farms vary by site and include increased production capacity, efficiency improvements, cost reduction, improved grid integration, preservation of employment, and increasing low-carbon electricity.

     Wind and solar power both have large land footprints and to be able to get more power out of the same amount of land with upgraded and repowered projects is desirable. According to the DOE, this is sort of equivalent to a brownfield/greenfield situation: “Wind repowering enables owners to retrofit power plants on existing sites with new and/or refurbished technology, including erecting taller, more efficient wind turbines to increase productivity. Repowered projects can often gain further cost-saving advantages, relative to new greenfield (or vacant-lot) developments, by using existing grid connections and infrastructure.” They also mention wind-heavy Denmark which has some very old wind projects still producing and who has been repowering those projects with better tech for many years. In 2019 wind repowering in Denmark represented a staggering 86% of gross added capacity and 87% of added wind turbines. From 2012 through 2019 Denmark had a 1.3 GW gain in capacity and a reduction of 109 wind turbines through repowering projects. Other repowering considerations in Europe and everywhere else for that matter include the benefits of reducing noise emissions, better aesthetics, and political considerations.

       

 

Wind Tech Advancements: Bigger is Better and More

 

     Height and turbine size increases have led to wind power efficiency improvements. Specifically, hub height and rotor diameter increases are the big factors in improving efficiency. Hub height refers to the distance from the ground to the hub of the turbine. According to the DOE: “hub height for utility-scale land-based wind turbines has increased 73% since 1998–1999, to about 98 meters (~322 feet) in 2022. That’s taller than the Statue of Liberty! The average hub height for offshore wind turbines in the United States is projected to grow even taller—from 100 meters (330 feet) in 2016 to about 150 meters (500 feet), or about the height of the Washington Monument, in 2035.”

 

Higher towers for wind turbines mean stronger higher altitude winds can be captured. Higher altitude winds have less friction from ground elevation variations, tall trees, and other land obstacles. As the figure below shows, most of the taller wind turbines are deployed in the windy areas of the Midwest and the hilltop elevations of the Northern Appalachian Mountains. Hub heights have increased fairly steadily for over a decade.

     Rotor diameters have also increased steadily through the past decade. According to the DOE: “Back in 2010, no turbines in the United States employed rotors that were 115 meters (380 feet) in diameter or larger. In 2022, the average rotor diameter of newly-installed wind turbines was over 130 meters (~430 feet)—longer than a football field, and almost twice the wingspan of a 747.”  A few days ago, I heard about a planned deployment of a wind turbine with a rotor diameter of around 900 feet. Longer turbine blades can capture more wind at any wind speed, including slower speeds. According to DOE: “Being able to harvest more wind at lower wind speeds can increase the number of areas available for wind development nationwide. Due to this trend, rotor swept areas have grown around 645% since 1998–1999.”

     Two drawbacks of larger turbine blades are transportation and installation challenges. Longer blades and taller tower sections are difficult to transport, especially around turns, under bridges, and highway overpasses. They can also be more difficult to install. These problems are being addressed.

     The largest wind turbine in the world became operational in 2023. It’s an offshore turbine, “the MySE 16-260, built by Mingyang Smart Energy for the China Three Gorges Corporation. It’s now operational and contributing to the power grid in China. Here are some impressive stats about this colossal turbine:

 

Rotor diameter: 260 meters (853 feet)

Swept area: 53,902 square meters (580,196 square feet)

Power output: 16 megawatts

Tower height: 152 meters (499 feet)

Generator weight: 349 metric tons (385 US tons)

Expected annual energy production: Around 66 gigawatt-hours, enough to supply approximately 36,000 homes.

 

 

Wind Repowering Economics

     A new report by Enverus concludes that wind repowering is gaining momentum. With significant cost increases for wind projects due to inflation and the cost of borrowing, more wind repowering projects are seeing better upsides than new builds. Choosing to repower over building new reduces capex and operation and maintenance costs and increases power production. Another advantage of repowering can be the ability to do it while keeping existing premium-priced power purchase agreements (PPAs) that have remaining time on the term of the agreement. Enverus quotes subsidiary Enverus Intelligence Research (EIR) VP Scott Wilmot: “Depending on PPA price, repower economics can be preferable to a new build if a 5% capacity factor gain can be realized. This is a low benchmark to clear given the turbine efficiency gains and degradation we have observed. Projects older than 12 years (pre-2012 vintage) can realize capacity factor gains of 10%-20% through a repower — this makes repowering an easy economic decision,” Wilmot said.

     Enverus also reports that the current repowering capacity at 7GW is about equal to new-build wind projects under construction. They also note that EIR identified 261 potential targets in its database representing almost 21,000 MW. Thus, it appears that wind repowering will continue to compete strongly with new builds. “Wind developers plan to add some 6.5-7.5 GW of energy to the grid through repowering projects in 2024. That means 2024 could tie 2019 for the most repowering projects in a single year.” Another advantage to repowering over new builds is that the interconnections are already there, as are the roads, prepared sites, permitting and regulatory approvals, and some other infrastructure. Wilmot predicts that wind repowering will continue to proliferate in the near to midterm as its economics continue to look better than keeping older underperforming projects online.

     The fact that wind repowering can happen fast, much faster than new builds, and can significantly increase the power output of a wind farm also means that it can quickly increase revenues not just for the developers but also for those who lease the land to them, who will also benefit from longer terms.

 

 

Stranding Some Assets Early Can Be Profitable

 

     Wind repowering is one example that shows that stranding some of these underperforming and inefficient (according to modern standards) projects can be economically wise. This is especially true for renewables that can still receive new production tax credits since they have been extended for another ten years in the U.S. Wind repowering also addresses land scarcity and mostly bypasses public opposition to new projects. These advantages can tip the scales and result in repowering being more economical than keeping older and inefficient projects online. Thus, early retirement of those original assets is a net benefit.  

 

 

References:

The upside of repowering wind: Why developers may blow new life into existing onshore over new builds. Enverus. January 31, 2024. The upside of repowering wind | Enverus

Repowering will represent nearly half of all new wind capacity in 2024: Enverus. Emma Penrod. Utility Dive. February 22, 2024. Repowering will represent nearly half of all new wind capacity in 2024: Enverus | Utility Dive

Repowering of wind farms: Do you know what repowering of wind farms is and how it is carried out? Iberdrola. Repowering of wind farms - Iberdrola

Wind Turbines: the Bigger, the Better. Liz Hartman. U.S. Dept. of Energy. Office of Energy Efficiency & Renewable Energy. August 24, 2023. Wind Turbines: the Bigger, the Better | Department of Energy

The Largest and Most Powerful Wind Turbine Ever Built Is Now Operational. David Nield. Science Alert. July 24, 2023. The Largest And Most Powerful Wind Turbine Ever Built Is Now Operational : ScienceAlert

 Wind Repowering Helps Set the Stage for Energy Transition. U.S. Dept. of Energy. Wind Technologies Office.June 2, 2021. Wind Repowering Helps Set the Stage for Energy Transition | Department of Energy

 Wind repowering: Unveiling a hidden asset. H. Doukas, A. Arsenopoulos, M. Lazoglou, A. Nikas, and A. Flamos. Renewable and Sustainable Energy Reviews. Volume 162, July 2022, 112457. Wind repowering: Unveiling a hidden asset - ScienceDirect

Rolling Coal: While the EPA Continues to Focus on Manufacturers and Sellers of Emissions Control Defeat Devices on Diesel Vehicles, Cummins Gets a Huge Fine for Installing Software That Cheats Emissions

 

     I heard a snippet from a Republican in the West Virginia legislature recently where the lawmaker noted that “rolling coal,” which refers to bypassing required emissions control on vehicles, and which can result in quite a bit of black smoke when accelerating, is obnoxious and potentially dangerous. The high level of black smoke has impeded the ability of other drivers to see and has caused accidents which include deaths.

     The EPA reported in 2020 that rolling coal was having a bigger cumulative effect on pollution than VW’s “dieselgate.” In the report the EPA’s Air Enforcement Division (AED) concluded that “the emissions controls have been removed from more than 550,000 diesel pickup trucks in the last decade. As a result of this tampering, more than 570,000 tons of excess oxides of nitrogen (NOx) and 5,000 tons of particulate matter (PM) will be emitted by these tampered trucks over the lifetime of the vehicles. These tampered trucks constitute approximately 15 percent of the national population of diesel trucks that were originally certified with emissions controls. But, due to their severe excess NOx emissions, these trucks have an air quality impact equivalent to adding more than 9 million additional (compliant, non- tampered) diesel pickup trucks to our roads.” The reality is that it is likely that the study far underestimates the actual number of trucks with the defeat devices installed. The analysis showed conclusively that evading emissions control rules is routinely practiced among owners of big diesel trucks. It is also routinely practiced among gasoline-powered vehicle owners and mechanics. I know this because I did it with an old Honda I had. When my auto-mechanic told me that my catalytic converter was not functioning correctly, he suggested that he could make a cut and bypass it. Being low on money at the time I said OK and let it go at that. Thus, I am guilty of this too, in my greed to save money. The vehicle was older at the time and within a year or two was junked out due to a rusted frame. However, I think that among those who do it routinely, it is not just about saving money. It is also about ‘giving the finger’ to the government and regulators like the EPA.

 

Source (for all): U.S. EPA.

 

Defeat Devices and Their History

 

     According to Wikipedia: “Defeat devices are mechanisms that interfere with or disable emissions controls in motor vehicles under real-world driving conditions, even if the vehicle passes formal emissions testing. These devices can have significant implications for both the environment and vehicle life. Let’s explore how they impact vehicles”:

 

“Emissions Control Bypass: Defeat devices bypass or eliminate emission controls, allowing vehicles to emit pollutants beyond legal limits. For instance, some devices alter engine performance during emissions tests, but revert to higher emissions during regular driving. This compromises air quality and contributes to health issues.”

 

“Some shops advertise “delete kits” as a way to improve mileage and extend component lifespan, saving customers money. However, these claims often lack scientific evidence, and the long-term impact on vehicle life is uncertain.”

 

     For diesel defeat devices, it is the owners of the vehicles that are buying and installing the widely available aftermarket defeat devices. Many of these devices can apparently also fool local and state inspections so that they pass. EPA found 28 companies responsible for making 45 illegal diesel tuners, as the investigation continues. The chart below shows the different types of defeat devices, their manufacturers, and how the supply chain works.

Source: U.S. EPA

     Defeat devices have a history that stretches to the 1970s when Chrysler, Ford, GM, and Toyota were ordered by the EPA to stop using ambient temperature switches which disabled pollution controls at low temperatures. Volkswagen was fined in 1973 for failing to disclose the presence of two temperature sensing switches that affected emissions. In 1995 GM was fined $11 million and ordered to recall 1991-1995 Cadillacs “for programming the car's electronic control unit (ECU) to enrich the fuel mixture any time the car's air conditioning or cabin heat was operating, since the EPA tests are conducted with those systems turned off. The richer fuel mixture was needed to address an engine stalling problem, resulting in emissions of up to 10 grams per mile of carbon monoxide (CO), nearly three times the limit of 3.4 g/mi. While the EPA and Justice Department contended that GM intentionally violated emissions standards, GM said that was "a matter of interpretation." Besides the fine, the second largest Clean Air Act penalty to date in 1995, GM had to spend up to $34 million for anti-pollution programs and recall 470,000 Cadillac 4.9 liter Eldorados, Fleetwoods, DeVilles, and Sevilles. The largest civil penalty under the Clean Air Act was $11.1 million paid by Louisiana-Pacific lumber and paper company.” Honda and Ford also faced big fines for defeat devices and deceptive emissions tallying practices in the 1990s. In 1998 seven diesel engine makers: “Caterpillar, Cummins, Detroit Diesel, Mack Trucks, Navistar International, Renault Trucks, and Volvo Trucks, also agreed to spend more than $1 billion to correct the problem. The trucks used engine ECU software to engage pollution controls during the 20-minute lab tests to verify compliance with the Clean Air Act, but then disable the emissions controls during normal highway cruising, emitting up to three times the maximum allowed NOx pollution.”

     EPA began fining companies making such devices several years ago, but the practice continues, the big fines continue, and it is uncertain how the fines are affecting proliferation, sales, and owner trends. Some diesel tuning equipment does not break any emissions rules, so the devices also need to be tested by EPA. In October 2023, CBS News reported that eBay was facing potential fines up to $2 billion for allowing the sale of defeat devices. Videos on social media have shown defeat device owners deliberately rolling coal in the faces of pedestrians, cyclists, and other motorists. While some people may like the smell of diesel, many of us do not like it, and it is of course, rude and obnoxious, as well as noxious. A few states such as Colorado and Maryland have banned rolling coal. It is indeed a violation of the Clean Air Act. There is likely a direct correlation between the proliferation of the devices and increased amounts of nitrogen oxides (NOx) and particulate matter (PM). eBay noted that they are already "blocking and removing more than 99.9% of the listings for the products cited by the DOJ, including millions of listings each year. "CBS News also reported that “California parts maker Sinister Mfg. Co. pleaded guilty to criminal charges and agreed to pay $1 million in fines for tampering with the monitoring device of an emissions control system of a diesel truck, the Justice Department said in August. The company sold nearly 40,000 defeat devices, including at least 35,960 kits that disable vehicles' exhaust gas recirculation systems, according to the agency.” Many of the devices sold are sold as diesel tuning kits rather than as “delete kits” which makes them harder to test and determine whether they are in violation. The Guardian reported in 2020 that crackdowns had yet to be effective: “Despite these actions, many companies continue to operate with impunity. The clearest evidence is the sheer number of tuners and straight pipes that appear to be openly sold on e-commerce sites, including eBay, and by users on Facebook’s Marketplace platform.”

     It was the Volkswagen scandal in 2013 and 2014 that led to increased scrutiny and fines for aftermarket defeat devices. Volkswagen paid $20 billion in fines for the fraud but emerged relatively unscathed due to large increases in vehicle sales to China in particular. I wonder how the companies producing the illegal devices are navigating the changes. Another tool for those hoping to stop the proliferation of such devices is suing the companies that make them on behalf of citizens with lung issues such as asthma. More stringent regulations in California have made the practice less common there and have made it more well-known that producers, sellers, and installers of such products are in violation of state and federal law. Europe also has a history of the use of defeat devices and other deceptive practices.

     Now in 2024 Cummins, once part of the $1 billion fine of seven diesel engine manufacturers in 1998, was fined $1.6 billion for essentially the same deception, this time for altering software to defeat pollution controls. Bypassing pollution controls is not legal for a manufacturer or for a consumer, but it has been done steadily for many years by both manufacturers and consumers. As a case, it perhaps shows the ambiguity of environmental statute vs. criminal law. Automotive manufacturers can apparently absorb fines and executives can apparently accept such risks to make a little more money. The persistence of the practice suggests that there is psychology at play. The devices are perhaps in a class like “fuzzbusters” but the fact is, they deliberately misrepresent facts and figures necessary to determine environmental impact. Both the companies and the consumers are wanting to fly under the radar and not be detected for cheating emissions. According to an article in The Cool Down:

 

“According to the Justice Department, Cummins rigged about 1 million Ram pickup trucks to cheat emissions tests so they looked cleaner than they actually are, reported The New York Times. As a result, 630,000 model year 2013-2019 Ram engines and 330,000 model year 2019-2023 Ram engines have secretly been releasing nitrogen oxide, which forms smog.”

 

“Violations of our environmental laws have a tangible impact,” Attorney General Merrick Garland said in a statement. “They inflict real harm on people in communities across the country.”

 

To settle these claims, Cummins has agreed to pay $1.6 billion to the state of California.

 

“The company has seen no evidence that anyone acted in bad faith and does not admit wrongdoing,” Cummins External Communications Director Jon Mills told Forbes.  

 

To recap, Cummins admits to deliberately deceiving the public and the EPA, after paying hefty fines for doing the same thing in 1998 and brushes it off by saying no one acted in bad faith and no one will admit wrongdoing. Is that an acceptable outcome, just absorbing a fine without any other consequences? It’s clear that those Dodge Rams were dodging their responsibility to follow statute, essentially cheating. Does or should cheating have further consequences beyond the fine? Clearly the deterrence of even hefty fines has not worked to make the practice less widespread.

 

References:

EPA Finds Rolling Coal Is Making Pollution Worse in America. Stef Schrader. The Drive. November 28, 2020. EPA Finds Rolling Coal Is Making Pollution Worse in America (thedrive.com)

Company fined nearly $2 billion over illegal modifications on pickup trucks: ‘They inflict real harm on people’. Leslie Sattler. The Cool Down. February 17, 2024. Company fined nearly $2 billion over illegal modifications on pickup trucks: ‘They inflict real harm on people’ (msn.com)

Re: Tampered Diesel Pickup Trucks: A Review ofAggregated Evidence from EPA Civil Enforcement Investigations. U.S. EPA. November 2020. full.pdf (nyt.com)

Ebay faces up to $2 billion in fines over selling "rolling coal" devices. Kate Gibson. Moneywatch. Updated on: October 17, 2023. Ebay faces up to $2 billion in fines over selling "rolling coal" devices - CBS News

Illegal devices that bypass vehicle emissions controls spread across US. Eli Wolfe and Alexandra Tempus. Fair Warning. Ed. Betsy Reed. The Guardian. September 9, 2020. Illegal devices that bypass vehicle emissions controls spread across US | US news | The Guardian

Defeat devices. Wikipedia. Defeat device - Wikipedia

 

Cryptocurrency Mining Energy Use: What are the Recent Trends and Reduction Possibilities?

 

     In late 2017 I wrote a detailed article on the excessive energy use of cryptocurrency mining. At that time, I was just trying to understand the process and the scope of cryptocurrency mining and the implications of its excessive energy use. The whole issue then was rather shocking to me in light of goals to reduce energy use and carbon emissions. Now, over 6 years later, I want to revisit the issue and see what has changed, both for better and for worse and see what can be done going forward to adequately address the issue. 

Bitcoin energy consumption worldwide from February 2017 to December 5, 2023 (in terawatt hours)

 

Source: Statista.

The Change Since My Previous Article. Source: Bitcoin Energy Consumption Index. (adapted). 

     The Energy Information Administration recently reported that: “preliminary estimates suggest that annual electricity use from cryptocurrency mining probably represents from 0.6% to 2.3% of U.S. electricity consumption.” They also note that monitoring the electricity use of the miners is not easy so that is why the estimates vary within such a big range. They utilize top-down and bottom-up approaches to determine energy use, but it is still difficult to know with certainty. As energy use rises for different reasons, grid planners such as the North American Electricity Reliability Corporation (NERC) have expressed concern about excessive electricity use by crypto miners. They also note that even though cryptocurrency mining began in the early-mid 2010s in the U.S. it took off heavily in China around 2019 but then as China began to crack down on it in 2021, much of the mining from China moved elsewhere, including to the U.S. I think that is what the Statista graph shows with a big rise followed by the plateau, then a big drop on the blue line. For the U.S. the bottom line is that the crackdown in China has led to a digital currency mining boom in the U.S. As big energy users, crypto miners can now participate in energy programs where they can be rewarded like other industrial energy users for powering down their mining during high-demand times. The EIA does hope to improve its estimates of U.S. crypto energy use in the future.  

 

     The graphs above clearly show that since I wrote my article, the energy use situation has not improved overall but has instead risen dramatically. When I wrote my article in December 2017 the minimum estimated TWh of electricity used for cryptocurrency mining was 15.5. In December 2023, that same number was 136.7 TWh, an 882% increase, or 8.82 times increase. Thus, what I was shocked about in 2017 has increased by nearly nine times! In terms of actual estimated use (the blue line on the graph) the increase during the same period was from 36.7 TWh to 137.7 TWh, or a 375% (3.75 times) increase. While that is a bit more manageable to wrap one’s head around, it is still a fairly massive increase. Also, according to the graph, the estimated use in late 2021/early 2022 was shockingly, over 200 TWh. That is a humongous waste of energy, equivalent to the annual energy use of multiple countries combined. Additionally, cryptocurrency mining also has a high water footprint. 

     When I wrote the original article it seemed hopeful that Ethereum’s change, termed the merge, from a proof-of work algorithm to a proof-of-stake algorithm was about to enter the fray and offer a much less power-hungry verification schema for transactions. Quite apparently, that effect has not yet materialized for crypto on the whole. I wrote then:

 

“The culprit is a power-hungry kind of algorithm that basically” crunches numbers.” Apparently, the current ‘consensus algorithm’ is Proof-of-Work which is very power hungry. Alternative algorithms like Proof-of-Stake consume negligible power in comparison but have yet to be proven. Another possible algorithm that is much less energy intensive is called Proof-of-Time-and-Storage. Utilizing this model has been called cryptocurrency “farming” rather than mining. However, it has yet to be launched and those who plan to launch it for their own cryptocurrency say there are still kinks to work out. Also, it is unclear how much energy it will save over current mining. Ethereum plans to offer a Proof-of-Stake model in 2018. The philosophy of Proof-of-Work has been summarized as “security comes from burning energy” since it is the most power-consumptive solution that leads to blockchain consensus. The philosophy of Proof-of-Stake has been summarized as “security comes from putting up economic value-at-loss.” Here any maliciousness is penalized so the threat of penalty discourages it. So, P-O-W is motivated by reward while P-O-S is motivated by punishment. In this case punishment is cheaper in energy expenditure than reward. Ethereum founder John Lilic notes that “mass adoption of Bitcoin across US households will result in very large increases of electricity use relative to existing financial systems.”

 

 

 

Not Just Unnecessary Excessive Energy Use but Enabling of Crime and Corruption

 

     In my original article, I also stated my distaste for cryptocurrency use, not only due to excessive energy use, but also due to its inconvenience for consumers and especially its preferred use by organized crime, criminal gangs, scammers, terrorist financing, sanctions busting, and other forms of corruption. None of these things offer any good to society. I would argue that these are very good reasons to eliminate or severely restrict cryptocurrency use. I do concede that there are some advantages of cryptocurrency use vs. traditional financing and accounting but they are not nearly enough to overcome the very real and damaging disadvantages. While many see cryptocurrency use as an evolved form of financing in line with the times where digitalization is king, the disadvantages are so intense as to render that view incorrect. Corruption is a huge problem all over the world and giving the corruptors powerful tools to better corrupt is obviously a support for them rather than a solution to any problems. The simple lack of trackability is a means for criminals to easily avoid the transparency and accountability that they seek to avoid. I also wrote about other issues such as “cryptojacking” where criminal enterprises diverted power to mine cryptocurrency and the less secure cryptocurrency trading exchanges were being targeted by malicious hackers.

     Blockchain technology can give added layers of security in needed ways other than in cryptocurrency mining. Thus, the use of power-hungry blockchain technology for these purposes is not problematic in the criminal sense. The use of blockchain tech for peer-to-peer power trading, smart grid tech, land registry and entitlement, and other electronic transactions and Internet-of-Things functions is established as beneficial for actually reducing hacking and corruption. Those transactions often have faster transaction confirmation times than cryptocurrency mining and thus use less energy. Participants are also known and tracked which takes out the anonymity that favors criminality in cryptocurrency transactions, where there is little to no record of who is doing what.

 

 

 

Proof-of Stake vs. Proof-of-Work, It’s Likely Effect on Crypto-Mining, Energy Use, and Participation

 

     When I wrote my original article it appeared that Ethereum was close to adopting their proof-of-stake algorithm but in fact they did not adopt it for transactions until September 2022, nearly 5 years later. They had stated previously that the change would put crypto miners out of work and drop energy use by over 99%. While that view is widespread, it seems that bigger players like Bitcoin are not planning to change from proof-of-work to proof-of-stake anytime soon.

     There are several advantages of proof-of-stake, one of the biggest being energy use. Another is obviously cost – less money to be paid to miners. There are some transaction and security advantages as well, such as more decentralization. There are also a few disadvantages. One is that participation by smaller players and entities is suppressed. While proof-of-stake offers more opportunities for more people to become validators, those validators will have to be people who own enough coins. Thus, it is likely that validators overall will become concentrated into fewer hands. There are also certain types of hacking attacks to which proof-of-stake can be more vulnerable.  

     According to a late-August 2023 article in Forbes there were then about 80 companies using proof-of-stake. Ethereum, with the second-highest market share after Bitcoin, is the biggest player and they are apparently still making the transition (after a year) to proof-of-stake. The article notes: “Proof of stake is becoming more prevalent as a consensus mechanism in the cryptocurrency world. There are currently about 80 different cryptocurrencies that use PoS as the consensus mechanism.” Even as that is the case, it is apparently a small amount of the total since cryptocurrency energy use continued to rise during the period from fall 2022 to fall 2023.  

     Ethereum gives some data and comparisons of energy use on their site that show that their “merge” from PoW to PoS, once completed, will drastically reduce energy use. There seems to be little doubt that PoS will change crypto energy use for the better. The sooner the better, anyone interested in pollution and the climate would be expected to say. Ascertaining the actual effect on climate is complicated by the fact that renewable energy as well as stranded energy resources are now employed in many crypto-mining operations. Some miners also set up ops near under-utilized power plants. This can help optimize the plants and improve their economics. Those plants might like selling more power but the effect on overall reliability is likely to be negative. The figures below show the comparisons of Ethereum’s PoW and post-merge PoS energy use to other industries and crypto ops.

 

Source of Figures: Ethereum.Org.

 

References:

 

Cryptocurrencies and Excessive Energy Use? The Surprising and Unsustainable Environmental and Climate Impacts of Bitcoin Mining: The Rise (and potential fall) of Cryptocurrencies and the Potential of Blockchain Technology. Kent C. Stewart. Blue Dragon Energy Blog. December 23, 2017. Blue Dragon Energy Blog: Cryptocurrencies and Excessive Energy Use? The Surprising and Unsustainable Environmental and Climate Impacts of Bitcoin Mining: The Rise (and potential fall) of Cryptocurrencies and the Potential of Blockchain Technology

Over 2 percent of the US’s electricity generation now goes to bitcoin. John Timmer. Ars technica. February 2, 2024. Over 2 percent of the US’s electricity generation now goes to bitcoin | Ars Technica

Tracking electricity consumption from U.S. cryptocurrency mining operations. Energy Information Administration. February 1, 2024. Tracking electricity consumption from U.S. cryptocurrency mining operations - U.S. Energy Information Administration (EIA)

Ethereum will use less energy now that it’s proof-of-stake. Elizabeth Lopatto. The Verge. September 15, 2022. Ethereum’s long-awaited switch to using less energy is here - The Verge

Ethereum's energy usage will soon decrease by ~99.95%. Carl Beekhuizen. Ethereum Foundation Blog. May 18, 2021. Ethereum's energy usage will soon decrease by ~99.95% | Ethereum Foundation Blog

Will Proof of Stake Kill Mining? (PoS vs PoW). Luke B. Solberg Invest.  October 1, 2021 (Updated 11. September 2022). Will Proof of Stake Kill Mining? (PoS vs PoW) (solberginvest.com)

Proof Of Stake Explained. E. Napoletano and Benjamin Curry. Forbes. August 25, 2023. What Is Proof of Stake? How Does It Work? – Forbes Advisor

Ethereum's energy expenditure. Ethereum.org. October 24, 2023. Ethereum Energy Consumption | ethereum.org

Bitcoin Energy Consumption Index. February 16, 2024. Bitcoin Energy Consumption Index - Digiconomist

Changing Power Demand Dynamics in the U.S.: Electrification Risks, Vulnerabilities, Preparation, and Fixes

 

     Electrification, particularly of heating and transportation, is often touted as necessary and sometimes as the main solution for lowering carbon emissions. While electrification is occurring, it has yet to replace much of traditional natural gas heating and the internal combustion engine for transport. Natural gas heating in the U.S. is more or less steady and flat. There has been no growth or reduction. Theat may change in the future. It should also be pointed out that natural gas also powers more of electricity than any other energy source. Thus, electrifying heat will not lower natural gas demand and consumption in the near term. Another near-term observation for EV transport is that due to the current inadequacy of charging infrastructure and EV ranges, most EV owners either also own an ICE vehicle or just travel less miles in their EV. That means that in terms of miles traveled, EVs are not replacing ICE vehicles as fast as purchasing data might suggest.

     With more electrification hitting U.S. power grids we are already seeing some power utilities report record power use during cold and hot weather events. Natural gas use on the grid has also had some record high use during these events. For instance, on January 16, 2024, the Tennessee Valley Authority (TVA) reported record power use, eclipsing their previous record in August 2007. Like ERCOT, PJM, and  many other power utilities and regional power authorities, they put out requests to customers for reduced power use during certain times. Luckily TVA, ERCOT, PJM, and the others had little, or no blackouts reported. However, they do acknowledge that they were close, and if more resources had tripped offline and/or if the weather and temperatures had been worse, there may have been significant blackouts. The main issue to point out is that power reliability is not as good as it could be. There are several reasons for this: more intermittent variable generation on grids, less baseload power on grids, less reserve capacity available in some regions, and insufficient grid upgrades to facilitate power importing/exporting between regions. The highest power demand day in the U.S. was in the hot summer of 2023. While summer demand can increase power demand to the highest levels, winter demand can often happen quickly and with extenuating factors like freeze-offs that can create more reliability problems.  

     Electric heat pump usage is increasing globally, with Asia, the U.S., and the E.U. leading the pack. IEA reports that in 2022, heat pump purchases exceeded fossil fuel heating system purchase for the first time with heat pumps making up 53% of new heating systems. Globally, heat pumps grew by 11% in 2022. In Europe, heat pump adoption grew strongly by 40% in 2022, with much of that due to high natural gas costs as a result of Russia invading Ukraine. Global EV sales grew by 25% in 2022 and by 55% in the U.S.

 

     Investments in heat pumps and EVs are considered to be investments in energy efficiency since electric motors are more efficient than ICE motors and heat pumps are more efficient than natural gas furnaces (although in the case of natural gas that is just for end use as life cycle efficiency for natural gas getting to those furnaces is more efficient than the electricity getting to those heat pumps).  The IEA reported that investments in energy efficiency were expected to reach $624 billion in 2023, rising from $600 billion in 2022, but they also cautioned that due to the increased cost of capital, those investments will not go as far as previously. Investments such as smart energy controls and building energy management systems are also included in energy efficiency investments associated with electrification.

 

     Groups like the North American Electric Reliability Corporation (NERC) are tasked with predicting reliability across different regions. They often sound alarms about vulnerabilities and suggest potential fixes. They note that in some cases where winter cold extends over much of the U.S., as much as 20% of power generation can go offline.

     It is good that there are now heat pumps that can function more efficiently in colder weather as I wrote about earlier this year. For those of us with older heat pumps, we are still vulnerable to very cold weather and must supplement. Sometimes, natural gas and propane furnaces and unvented heaters can run without electricity which is nice if you experience frequent blackouts. In those cases, electrification of heat is a much higher vulnerability than gas heat.

     In different regions of the U.S. there are much different power dynamics for home heating. In the south and southeast most homes are heated with electricity and in the north, most are heated with natural gas. That means there is more vulnerability in the south as we saw during the devastating winter storm Uri in February 2021. Grid operators like New England ISO are predicting steadily rising winter demand peaks into the next decade, partially due to increased electrification.

     While electrification advocates often point out that smart power management can smooth out and offset some of those peaks, I would not suggest relying on this along with requests to reduce usage. It is not a very thorough or solid reliability plan, but rather more of a supplemental help plan. Grid-scale batteries, home batteries, home insulation, virtual power plants, and the like can also help, but only when deployed at high levels and adequately pre-charged for extreme weather events. Relying on them now is more tenuous.

 

 

References:

Your home’s cleaner, better heating system comes with one major cost. Umair Irfan. Vox. January 23, 2024. Your home’s cleaner, better heating system comes with one major cost (msn.com)

TVA hits peak, record-setting demand, no blackouts reported. Dallas Payeton. Local 3 News. January 17, 2024. TVA hits peak, record-setting demand, no blackouts reported | Local News | local3news.com

Global heat pump sales continue double-digit growth. Yannick Monschauer. Chiara Delmastro. Rafael Martinez-Gordon. Commentary — 31 March 2023. International Energy Agency. Global heat pump sales continue double-digit growth – Analysis - IEA

US residential heat pump sales pass gas furnaces for first time as interest in efficiency tech surges: IEA. June 7, 2023. Robert Walton. Utility Dive. US residential heat pump sales pass gas furnaces for first time as interest in efficiency tech surges: IEA | Utility Dive

Extracting Rare Earth Elements and Critical Minerals from Coal Refuse Tailings, Coal Ash, Acid Mine Drainage, Fire Clays, and Tonsteins

     In my deep dive post into brine mining, I noted that it is not economic to extract rare earth elements (REEs) from oilfield and geothermal brines. Concentrations are not high enough. However, it appears that it can be economic to extract REEs from acid mine drainage (AMD), coal refuse or spoils, and especially clay beds associated with coal beds that are often part of coal spoils, as well as coal itself and coal ash. Some researchers think we can meet half or more of our REE requirements from such sources sometime in the 2030s. Currently, the U.S. imports more than 80% of its needed REEs from China. The U.S. uses about 15,000 tons of REEs per year. That dependence on China is concerning. Contrary to the name, rare earth elements are not rare. However, they do not occur in high concentrations so one could say that concentrated sources of REEs are indeed rare.  

 

Rare Earth Elements (REEs)

     According to a February 2021 paper in the Journal of Geochemical Exploration: “Rare earth elements (REE) are a group of 17 elements including lanthanides (La-Lu), Sc and Y. REE are often divided into two groups: light REE (LREE; La to Gd) and heavy REE (HREE; Tb to Lu, and including Sc and Y). However, there is no consensus on the definition of HREE and LREE in the scientific community, as in some cases, LREE and HREE do not include the same elements. In addition, REE are sometimes divided into three groups: LREE (La to Pm), medium REE (MREE; Sm to Gd) and HREE (Tb to Lu, and including Sc and Y) or can be defined as critical REE or non-critical REE (based on market demand), with no specific definition of the REE considered in each class.” The figure below from the DOE’s NETL shows the position of REEs and CMs in the periodic table of elements.

 

 

China’s Control of REE Processing and Making of REE Magnets

 

     As mentioned, we get the vast majority of REEs and REE magnets from China. China controls about 90% of the world’s REE processing capacity, including purifying REEs to magnet-grade. China has had in place a ban on technology to extract and separate REEs, presumably via solvent extraction, which is a process with very significant negative environmental impacts. Due to these pollution concerns as well as technical complexity, firms in the “West” have struggled to develop comparable solvent extraction recovery of REEs. China has also strengthened export controls on other critical minerals like graphite and the chip-making mineral gallium and germanium. All of these controls are a ploy to maintain market dominance. They refer to them as means to protect national security and public interest.

     The latest Chinese move in late December 2023 is a ban on the export of technology to make rare earth magnets. According to Reuters this includes “technology to prepare smarium-cobalt magnets, neodymium-iron-boron magnets and cerium magnets to its "Catalogue of Technologies Prohibited and Restricted from Export." “In the list it also banned technology to make rare-earth calcium oxyborate and production technology for rare earth metals, adding them to a previous ban on production of rare earth alloy materials.” China is driven to maintain this control and very strong government subsidization helps them to do so.

 

 

Coal Refuse

 

     Coal mining, processing and combustion produce quite a lot of waste. On the mining and processing side this includes leftover piles of tailings that includes rock, shale, slurry, slate, clay, and other materials.

Runoff from such waste can be environmentally destructive, causing acid mine drainage and leaching iron, manganese, and aluminum into waterways. For every ton of coal mined there is about 880lbs of waste, some of which is missed coal. This waste is also flammable and can ignite to form fires that are difficult to extinguish. In some cases, the waste coal can be recovered through remining which can make a mining site less environmentally destructive than before it was remined. Coal combustion waste includes fly ash, bottom ash, and slag. Every 100 tons of coal that is burned produces about 85 tons of coal ash. Fly ash is the most voluminous type of combustion waste (about 80%) and along with bottom ash is stored in very large sludge ponds near coal-fired power plants. These coal ash impoundments can be a major source of local pollution of soil, surface water, and groundwater with heavy metals if they leak or overflow. Some waste coal is reprocessed and burned in waste coal-burning plants, although they produce more environmental toxins. Fly ash is used in concrete. The ash is also alkaline and when incorporated into the acidic coal mining and processing tailings, usually by encapsulating the tailings in the ash sludge, can reduce the acid mine drainage that it produces.

     The average REE concentration in the world’s coals is about 68.5 ppm. Coal refuse such as coal ash has enhanced concentrations, with an average REE concentration in coal ash of 403.5 ppm. That is a higher concentration for coal ash than most AMD. However, the REEs in coal ash are not as easily liberated as those in AMD since the AMD has already undergone significant acid leaching and coal refuse may require calcination, which requires heat and has high CO2 emissions, to enhance and optimize recovery of REEs.

 

 

 

Extracting REEs and Critical Minerals from Coal Byproducts and Refuse

 

     A new potential use for both coal tailings refuse and coal combustion ash is extraction of REEs. REEs may also be extracted from coal itself and from clay beds over or under coal beds. Particular kinds of REE-enriched clay beds known as tonsteins can be the most lucrative for REE extraction. Acid mine drainage (AMD) is the most voluminous source of potential REEs from coal refuse. The DOE’s National Energy Technology Lab (NETL) is working with Ohio State University to develop REE extraction methods and projects. They note the scope of the resource in the region and elsewhere in the U.S. According to Ohio State University: “There are 6,000 recorded abandoned mines in Ohio alone, while 4,000 miles of streams in Appalachia and 5,000–10,000 miles of streams in the western United States have been affected by acid mine drainage; those sites can serve as a foundation for future production of REEs.” In 2005 the EPA put AMD affected streams at 12,000 miles. There are different processes that can extract REEs from coal refuse, which I will describe in the next section.

     Essentially, the acidity of coal refuse produces sulfuric acid in runoff which leaches out minerals and metals, including REEs and critical minerals. Thus, nature performs the first step in concentrating these materials. The source of the AMD containing REEs and critical minerals is the exposure and oxidation of pyrite (FeS2). A summary of the reactions is as follows:

 

2 FeS2+7 O2+2 H2O → 2 FeSO4-+2 H2SO4

Pyrite + Oxygen + Water → Ferrous Sulfate + Sulfuric Acid

 

Thus, it appears that pyrite, commonly known as ”fool’s gold,” will perhaps become a source of wealth after all!

     In addition to the REEs, there are critical minerals that can be extracted from AMD and other coal refuse. These include cobalt which is vital for many types of lithium-ion batteries in current use. Other critical minerals that can be extracted include nickel, manganese and aluminum.

     Coal refuse is not the only potential industrial source of REEs/CMs. Residue from uranium mines and phosphogypsum waste from phosphate fertilizer production are other potential industrial sources. Bauxite residues and metallurgical slags are other potential minor sources.

     Many universities, institutes, and other public and private entities are involved in REE/CM research projects, particularly in the Appalachian region which has high concentrations.

 

 

Environmental Impacts of Existing Global REE Mining and Processing

 

     Environmental impacts of existing global REE mining and processing projects can vary considerably based on ore mineral type. A Life Cycle Analysis (LCA) study in 2022 went through the potential environmental impacts of each process in the workflow from mining through processing of different ore types and determined which process had the most potential for improvement of environmental impacts. Identified impacts include those from acidification, eutrophication, and toxicities such as radioactive dust. Other impacts include those from the energy intensity of the mining and processing, including the need for heat, and the climate impacts of those processes. The figure below from the paper shows a simplified version of the chemical process chain of typical REE mining and processing from mineral ores.

 

 

 

Ion Exchange Chromatography Separation of REEs

 

     In China, most REE extraction from rock ore is now done by ion exchange. This process also works for recovering REEs from AMD and other coal refuse. Techniques using ammonium sulfate, ionic liquids, and eutectic solvent as lixiviants, have been successful. Ion exchange chromatography does not inherently require the use of solvents for extraction, although some may be used in limited amounts in some forms of the process. In ore-based mines there is considerable solvent extraction used, often in conjunction with ion exchange techniques. Extraction via solvents is not at all environmentally benign as solvent management is always an issue. Leaching agents such as hydrochloric acid and hydrofluoric acid can be toxic, often as they have been left as highly acidic ponds. Ion exchange works simply by attracting positively changed cations and negatively changed anions as a means of separation.  

 

 

The Trap-Extract-Precipitate (TEP) Process for REE Extraction

 

       According to Ohio State University, the three-stage trap-extract-precipitate (TEP) process for REE extraction is both very effective at extracting high levels of REEs and environmentally benign. The TEP process utilizes industrial by-products to trap the REEs and an organic chelating agent to recover the REEs from the mine drainage.  They report: “This approach generates lower post-extraction waste and minimizes the associated environmental impacts when compared with other REE extraction techniques. The TEP process retains more than 99 percent of the REEs and produces solids that contain more than 7 wt. percent (70,000 ppm) total REEs.”

 

American Resources’ ReElement Technology: Ligand-Assisted Chromatographic Separation and Purification Resulting in 99.5% Pure REEs and Critical Minerals

     In late 2020 mining company American Resources formed a new subsidiary, American Rare Earth, to extract REEs in Kentucky. Sites in Eastern Kentucky, in Letcher, Knott, and Pike Counties. The company reported then that “American Rare Earth's initial site has the ability to produce rare earth oxides having a mix of approximately 20% neodymium, praseodymium and dysprosium, in addition to healthy levels of cobalt and lithium, all important elements used in the production of permanent magnets, electric vehicles (EVs) and other technologies.” Refuse and AMD from the REE-enriched Dean Coal, or Fire Clay Coal, which is described later in this post, is to be the main source of the coal-based REEs/CMs. In early 2021, the company acquired exclusive rights to critical REE separation and purification technologies from Hasler Ventures LLC and Purdue University. The environmentally safe method uses ligand-assisted chromatography for the separation and purification of REEs and CMs from coal, coal refuse, recycled permanent magnets, and lithium-ion batteries. It can also be used for REE/CM-rich ore from REE/CM mines. Thus, the method can also be employed as a means of recycling REEs and CMs from e-waste. Professor Linda Wang at Purdue was the main developer of the technology and Don Hasler, retired from Purdue, formed Hasler Ventures, and optioned the technology, and licensed it to American Resources. The tech is also known as ligand-assisted displacement chromatography or LAD chromatography. After subsequent development of the process by Hassler and American Resources, they plan to sublicense the technology to other companies. The figure below depicts the process.

 

 

    

New Technique Being Developed to Extract REEs from Recycled Product Components Utilizing Genetically Modified Bacteria

     A December 2023 paper in the journal Synthetic Biology describes a new technique using genetically modified bacteria to extract REEs from recycled product components. The process uses a modified version of bacterium Vibrio natriegens to extract the REEs through a process known as biosorption. The study involved testing many different modified versions of the bacterium. It was found that one of these mutants boosted extraction by 210% as compared with unmodified V. natriegens. Although this method is considered to be in the early stages it may one day be able to replace solvent extraction as the main method for extracting REEs.

 

The Win-Win-Win of AMD Remediation, REEs/Critical Minerals Extraction, and Domestic Production

     While currently it is more expensive to extract REEs and critical minerals from AMD than to get REEs from ore deposits, the process has co-benefits that make it quite desirable. The costs are also expected to come down and perhaps one day be competitive with ore deposits. Mining REEs and critical minerals from ore deposits creates new environmental impacts but getting them from AMD and other coal refuse helps to remediate past environmental impacts since a necessary step in the process is water treatment. For countries like the U.S., it also helps develop strategic domestic supplies of these key resources. One of the keys to success is to treat the AMD before it gets a chance to enter streams. The potential additional revenue stream to states for REE/CM extraction from AMD could be vital since in some states such as West Virginia, mine reclamation funds are nearing insolvency.

 

Economics of REE/CM Recovery from Coal Refuse Require Consideration of Co-Benefits

     While there is an abundance of acid mine drainage that continues to pollute streams and that can be a feedstock for these materials, it is not currently economical to do so and it is unlikely to be in the future, even with technological improvements. The process will continue to require subsidization. However, the co-benefits of cleaning up streams and reducing dependence on China help to keep the projects going. Another co-benefit being explored by Ohio University and local environmental groups is collecting and concentrating iron oxides from AMD to make pigments for paints, bricks, and tiles. Such projects can provide additional revenue streams for AMD treatment.

 

The Mount Storm REE Recovery Project from Acid Mine Drainage in Northern West Virginia: A Functional Demonstration Project that Can Potentially Refine AMD from Different Sources

     The West Virginia Water Research Institute (WVWRI), led by Paul Ziemkiewicz, began working with REE extraction in 2016 and began operating a pilot REE/CM extraction plant at Mount Storm in Northern West Virginia in 2018, recovering the minerals from AMD. The project was awarded $5 million in late 2019 to scale up. Ziemkiewicz describes AMD treatment as an environmental obligation and REE recovery from such treatment as an opportunity. The scale-up involves partners from the private sector including Rockwell Automation, L3Eng, SNF Chemicals, Solmax, Endress, and Hauser as well as the West Virginia DEP. According to WVU Today: “The facility can treat up to 500 gallons per minute of AMD from an adjacent coal property while producing nearly two tons per year of REEs and CMs in the form of mixed oxides. The Mount Storm site is online producing compliant discharge water and, as of Sept. 2022, the system began production of hydraulic preconcentrate.” The project received $8 million in new funding from the DOE in the spring of 2023. Ziemkiewicz also points out other advantages of AMD as a feedstock for extraction projects including the fact that the sites are already permitted. He projects that 5.4% and 7.3% of the global requirements for Terbium and Dysprosium, two of the most sought-after and critical REEs, can eventually be produced by this facility alone. Ziemkiewicz also noted “that over 60% of the rare earths in AMD are neodymium, praseodymium and the heavy REEs that are most utilized in green energy and defense technologies. That number far surpasses the 12% HREE produced at typical REE mines.” Thus, it can be discerned that this is a very important project and others like it can eventually help to develop a strong domestic REE/CM industry that has less net environmental impact than REE mines which often result in a significant amount of waste that is low-level radioactive, with uranium and thorium in the waste. The WVWRI is also involved in a project to process AMD from a non-coal mine near Butte, Montana, for REE extraction, working with the DOE and other entities. The AMD from that mine and potentially several others, will be shipped to what they are calling the Central Refinery in Mount Storm for processing.

 

 

REE Enrichment in Coal Regions

There is considerable variability of REE enrichment in AMD in different areas and more specifically in different coals and underclays. There are economic limits to extractable REEs in particular coals and coal wastes from different coals and underclays. Cutoffs for REE enrichment lower limits are usually considered to be somewhere between 250-350ppm. A 2021 study in Ohio coals sampled 234 coal sites for REE enrichment using portable X-ray fluorescence (XRF), which is satisfactory for field sampling but less accurate than desktop XRF/XRD analysis. Some results of the study are shown below where several samples are considered to have sufficient REE enrichment for extraction. Additionally, different coals, underclays, and subsequent refuse vary in ratios of different kinds of REEs (light REEs vs. heavy REEs) and CMs, which can also change the economics of extracting those resources.

     A study published in May 2020 in Fuel summarized the mechanisms for REE-enrichment in coals: “Four main genetic modes of REE enrichment in coals have been identified: terrigenous, tuffaceous, infiltrational, and hydrothermal [6], [7]. REE contents in the different strata of the same coal deposit may vary significantly.” The study also noted the most enriched coals in Kentucky, China, and the Russian Far East.

 

 

 

Tonsteins and Fire Clays: Altered Volcanic Ash Layers of Kaolinite Clay that are Enriched in REEs: The Fire Clay Coal Seam REE Play in Eastern Kentucky

 

 

     Some of the best resources in coal regions for REE extraction are altered volcanic ash layers deposited in coal forming swamps. Such altered volcanic ash often yields high-purity kaolinite clay. These deposits are known as tonstiens and can host very good REE deposits of high concentration. One of the most prominent and most enriched of these tonsteins is one deposited within the Fire Clay Coal seam in southeast Kentucky where REE concentrations as high as 4198 ppm have been recorded. The Fire Clay tonstein is a kaolinized, airfall volcanic ash bed that was deposited in a widespread late Carboniferous peat-forming mire. The tonstein in the Dean Coal, known more commonly as the Fire Clay Coal, is nearly as laterally extensive as the coal itself but in some places, there is no tonstein but still high REE concentrations. There, it is thought that the ash was emplaced but not hydrothermally altered. The source of the volcanic activity that delivered the ash in Middle Pennsylvanian times is thought to be in the Arkansas region. The emplacement of the Pine Mountain thrust sheet in later Pennsylvanian times as part of the Alleghenian orogeny to the south, mostly in Southwest Virginia, is thought to have been the source for the hydrothermal activity that led to the hydrothermal alteration of the ash layers.

     Another Eastern Kentucky coal seam, the Manchester seam, also has very high REE concentrations rivaling those of the Fire Clay seam, with some over 2000 ppm reported in Clay County, Kentucky. However, this Middle Pennsylvanian coal is not known to have any volcanic ash or volcanic influence, so for now it is an enigma. Perhaps the ash layer was more diluted, as some researchers have suggested. However, the Fire Clay coal and tonstein are consistently REE-enriched and much more laterally extensive and thus should be considered to be the most prominent REE coal/tonstein play in Appalachia and probably the U.S.  

Source: Lanthanide, yttrium, and zirconium anomalies in the Fire Clay coal bed, Eastern Kentucky. James C Hower, Leslie Ruppert, and Cortland F. Eble. International Journal of Coal Geology 39(s 1–3):141–153. 1999. (PDF) Lanthanide, yttrium, and zirconium anomalies in the Fire Clay coal bed, Eastern Kentucky (researchgate.net)

Source: US Geological Survey.

     According to a May 2020 paper in Fuel: “the flint clay parting of the Fire Clay coal seam contained 490 ppm of REEs on a whole sample basis, which is much higher than the other strata of the seam (Hower et al., 1999). A sample collected from the immediate floor of a coal from the Guxu Coalfield (located in the southeastern part of Sichuan Province, China) contained as high as 1877 ppm of REEs, which is nearly an order-of-magnitude higher than the coal strata.” Coals from the Russian Far East also have high REE concentrations. However, since both China and Russia are unsatisfactory as suppliers of these needed materials for geopolitical reasons, countries of the so-called free world are necessarily looking for their own best sources.

 

 

Calcination Improves Leaching Recovery of REEs from Coal Waste and the Potential of Coal Ash as a Feedstock

     Acid leaching, as occurs in the formation of AMD, is what provides the first step in concentrating REE’s in AMD. Acid leaching can be improved when treating coal refuse such as coal ash through calcination so that more REE’s and CMs are recovered. Calcination involves adding limestone and significant heat (unfortunately both high CO2-emitting processes) which chemically alters clays and makes insoluble materials soluble. Thus, while coal ash may have higher concentrations of REEs than other coal refuse and AMD, the higher emissions from calcination may make extracting them from the ash less desirable.  

     A study published in Fuel in May 2022 showed that calcination improves REE recovery percentages and offers two mechanisms: “(1) decomposition of difficult-to-dissolve REE-bearing minerals into soluble forms; and (2) liberation of REE-bearing minerals encapsulated in clays after calcination due to the dehydration and disintegration of the layered clay structure.” It was also noted that there was no direct evidence for these mechanisms. The study involved recovery from the REE-enriched Fire Clay in Eastern Kentucky and the Western Kentucky No. 13 coal seam. In the study scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) analysis were used. According to the study’s conclusions “enhanced REE recovery from the Western Kentucky No. 13 and Fire Clay coal wastes caused by calcination at 600 °C without adding any additives. Acid leaching test results showed that after the calcination pretreatment, the recovery of TREEs from the coal waste of the two different seams increased by 52 and 17 absolute percentage points, respectively.”

     Thus, it appears that calcination will be one key to enhancing recovery from coal refuse. I would also guess that carbon capture and sequestration during the calcination process will be proposed as it has been for calcination in the manufacture of concrete.

     Coal ash has some advantages and disadvantages as a potential feedstock for REEs/CMs. While concentrations average about 400 ppm globally, in the Southern Appalachian Basin region they can average 500 ppm. Coal ash is captured in a granular, crushed state, which can provide easier access to REEs/CMs.

     The American Chemical Society’s Environmental Science Technology published a paper in March 2023 about a new “green” process for REE recovery from coal fly ash (CFA). According to the paper’s abstract: “This study demonstrates a green system for REE recovery from Class F and C CFA that consists of three modules: REE leaching using citrate, REE separation and concentration using oxalate, and zeolite synthesis using secondary wastes from Modules I and II. In Module I, ∼10 and 60% REEs were leached from the Class F and C CFA samples, respectively, using citrate at pH 4. In Module II, the addition of oxalate selectively precipitated and concentrated REEs from the leachate via the formation of weddellite (CaC2O4·2H2O), while other trace metals remained in solution. In Module III, zeolite was synthesized using wastes from Modules I and II. This study is characterized by the successful recovery of REEs and upcycling of secondary wastes, which addresses both REE recovery and CFA management challenges.” This multi-step process looks promising for REE recovery from coal fly ash. A model of the process is shown below.

 

Other processes for liberating higher percentages of REEs from coal ash include calcination, as mentioned, and chemical roasting using sodium hydroxide and other alkaline materials.

 

U.S. Government Incentives for Domestic Critical Minerals, Including REEs, Ownership Delineation, and Other Regulatory Concerns

 

     In early August 2021, the bipartisan Rare Earth Manufacturing Production Tax Credit was introduced by Eric Swalwell (D) and Guy Rosenthaler (R). This would provide a tax credit for mining and processing of REEs at $20 per kilogram for domestically produced rare earth magnets. If all component rare earth material is made or recycled in the U.S, the credit increases to $30 per kg. This was reintroduced in the House as H.R. 2849, the Rare Earth Magnet Manufacturing Production Tax Credit Act of 2023 in April 2023:

 

“This bill allows a new tax credit for the domestic production of rare earth magnets. The magnets must be manufactured or produced in the ordinary course of the taxpayer's trade or business. The credit is disallowed if any component rare earth material used to produce such magnets is produced in a non-allied foreign nation.”

 

“The bill defines rare earth magnet as a permanent magnet comprised of an alloy of neodymium, iron, and boron, or an alloy of samarium and cobalt, which may also include other material.”

 

This bill has yet to be enacted and is now considered unlikely to be enacted as is in the near term.

     Peter Cook and Seaver Wang argue in a recent Breakthrough Institute article that critical minerals regulation and incentivization need to be updated and regulated separate from other minerals and materials. They are currently regulated along with other minerals under the Mineral Leasing Act of 1920 (MLA) and the Materials Act of 1947. They argue for a separate regulatory classification for critical minerals. They note: “A principal benefit of a separate regulatory classification for critical minerals is that it would enable land management agencies to preemptively complete related work that is necessary for permitting new mine projects. Currently, agencies complete this work much later, after an operator has already applied to develop a mine. A separate classification would allow Congress and agencies to design, fund, and staff programs that target areas with critical minerals resources and proactively complete steps in the environmental review process, like baseline data collection, ecological assessments, and cultural resource inventories.” They also advocate for other common-sense ways to simplify and speed up permitting for CMs. The goal is for regulatory agencies to have a classification framework for CMs that matches that of the USGS. There are concerns that a mad rush for domestic CMs would invite environmental damage. The article mostly addresses concerns with mining CMs rather than extracting them from existing waste streams, so it is probably not very relevant to this post. Most REE/CM extraction from these sources is likely already free to take place without much regulatory red tape as in many cases such as AMD, there are net environmental benefits to the extraction.  

     The state of West Virginia worked on House Bill 4003 from 2021 and it passed the Senate in March 2022. This bill promotes REE/CM extraction from AMD and other coal refuse and clarifies ownership of extraction projects and profits. Paul Ziemkiewicz, who directs the West Virginia Water Research Institute, has been instrumental in developing REE/CM recovery projects in West Virginia and in making suggestions to government regarding ownership. According to WVU Today:

 

“HB 4003 would follow through on Ziemkiewicz’s suggestion to state lawmakers that they clarify who owns the resources resulting from treated acid mine drainage.”

 

“Ziemkiewicz has also said rare earth element recovery could supply financial support for state mine cleanup funding.”

 

“HB 4003 specifies that all funds received by the state Department of Environmental Protection from commercial benefit from mine drainage treatment would go into the agency’s Special Reclamation Water Trust Fund or a set-aside fund for acid mine drainage.”

 

Another bill pending in the state, House Bill 4025, offers 5-year exemptions from severance tax for projects extracting REEs and CMs.

 

 

References:

Ohio State University Researchers Demonstrate REE Recovery Process. U.S. Dept. of Energy. Office of Fossil Energy and Carbon Management. January 15, 2020. Ohio State University Researchers Demonstrate REE Recovery Process | Department of Energy

Recovery potential of rare earth elements from mining and industrial residues: A review and cases studies. Sophie Costis, Kristin K. Mueller, Lucie Coudert, Carmen Mihaela Neculita, Nicolas Reynier, and Jean-Francois Blais. Journal of Geochemical Exploration. Volume 221, February 2021, 106699. Recovery potential of rare earth elements from mining and industrial residues: A review and cases studies - ScienceDirect

In coal country, a new chance to clean up a toxic legacy. Austyn Gaffney and Dane Rhys. Washington Post. May 19, 2022. Coal states explore how to recyle metals and rare earths from mine waste - The Washington Post

Rare earth elements from waste. Bing Deng, Xin Wang, Duy Xuan Luong, Robert A. Carter, Zhe Wang, Mason B. Tomson, and James M. Tour. Science Advances. Vol 8, Issue 6. February 9, 2022. Rare earth elements from waste | Science Advances

Remining in Ohio. Ohio Dept. of Natural Resources. Youtube. Bing Videos

Rare earth elements from coal and coal discard – A review. Orevaoghene Eterigho-Ikelegbe, Hamza Harrar, and Samson Bada. Minerals Engineering. Volume 173, 1 November 2021, 107187. Rare earth elements from coal and coal discard – A review - ScienceDirect

Rare earth element resource evaluation of coal byproducts: A case study from the Powder River Basin, Wyoming. D.A. Bagdonas, A.J. Enriquez, K.A. Coddington, D.C. Finnoff, J.F. McLaughlin, M.D. Bazilian, E.H. Phillips, T.L. McLing. Renewable and Sustainable Energy Reviews. Volume 158, April 2022, 112148. Rare earth element resource evaluation of coal byproducts: A case study from the Powder River Basin, Wyoming - ScienceDirect

Qualitative Rare Earth Element Analysis of Ohio Underclays using Portable X-Ray Fluorescense. Samuel R.W. Hulett, Franklin L. Fugitt, and Christopher E. Wright. Ohio Department of Natural Resources, Division of Geological Survey. AAPG_Clay REE_v2 copy (ohiodnr.gov)

Extraction Kinetics of Rare Earth Elements from Ion-Adsorbed Underclays. Priscilla Prem, Ward Burgess, Jon Yang, and Circe Verba. Minerals 2023, 13(12), 1503. November 30, 2023. Minerals | Free Full-Text | Extraction Kinetics of Rare Earth Elements from Ion-Adsorbed Underclays (mdpi.com)

Rare earth discoveries mean coal mines could have a key role to play in the energy transition. Anmar Frangoul. CNBC. November 24, 2023. Rare earth discoveries mean coal mines could have a key role to play in the energy transition (msn.com)

WVU researchers earn $8M for rare earth extraction facility, an economic and environmental game changer. WVU Today. Wednesday, April 5, 2023. WVU researchers earn $8M for rare earth extraction facility, an economic and environmental game changer | WVU Today | West Virginia University

WVU awarded $5 million to continue rare earth project, build acid mine drainage treatment facility. WVU Today. Tuesday, October 1, 2019. WVU awarded $5 million to continue rare earth project, build acid mine drainage treatment facility | WVU Today | West Virginia University

North Dakota researchers find cost-effective way to extract rare-earth elements from coal. Dan Gunderson. MPR News. Grand Forks, N.D. December 8, 2023. North Dakota researchers find cost-effective way to extract rare-earth elements from coal | MPR News

Aspects of rare earth element enrichment in Central Appalachian coals. James C. Hower, Cortland F. Eble, Jason S. Backus, Panpan Xie, Jingjing Liu, Biao Fu, and Madison M. Hood. Applied Geochemistry. Volume 120, September 2020, 104676. Aspects of rare earth element enrichment in Central Appalachian coals - ScienceDirect

Characterization and recovery of rare earth elements and other critical metals (Co, Cr, Li, Mn, Sr, and V) from the calcination products of a coal refuse sample. Wencai Zhang and Rick Honaker. Fuel. Volume 267, 1 May 2020, 117236. Characterization and recovery of rare earth elements and other critical metals (Co, Cr, Li, Mn, Sr, and V) from the calcination products of a coal refuse sample - ScienceDirect

Lanthanide, yttrium, and zirconium anomalies in the Fire Clay coal bed, Eastern Kentucky. James C Hower, Leslie F Ruppert, and Cortland F Eble. International Journal of Coal Geology. Volume 39, Issues 1–3, March 1999, Pages 141-153. Lanthanide, yttrium, and zirconium anomalies in the Fire Clay coal bed, Eastern Kentucky - ScienceDirect

Tonstein. Wikipedia. Tonstein - Wikipedia

Seatearth. Wikipedia. Seatearth - Wikipedia

The origin of tonsteins, an overview, and links with seatearths, fireclays and fragmental clay rocks. D.A. Spears. International Journal of Coal Geology. Volume 94, 1 May 2012, Pages 22-31. The origin of tonsteins, an overview, and links with seatearths, fireclays and fragmental clay rocks - ScienceDirect

Mineralogy, Geochemistry, and Genesis of Kaolinitic Claystone Deposits in the Datong Coalfield, Northern China. Linsong Liu, Qinfu Liu, Thomas Algeo, Hao Zhang, Yongjie Yang, Gaoyu Peng, Shuai Zhang, Hanlie Hong & Di Liu. Clays and Clay Minerals. 69, pages68–93 (April 2021). Mineralogy, Geochemistry, and Genesis of Kaolinitic Claystone Deposits in the Datong Coalfield, Northern China | Clays and Clay Minerals (springer.com)

A Study on Removal of Rare Earth Elements from U.S. Coal Byproducts by Ion Exchange. Peter L. Rozelle, Aditi B. Khadilkar, Nuerxida Pulati, Nari Soundarrajan, Mark S. Klima, Morgan M. Mosser, Charles E. Miller & Sarma V. Pisupati. Metallurgical and Materials Transactions E.  volume 3, pages6–17 (2016). A Study on Removal of Rare Earth Elements from U.S. Coal Byproducts by Ion Exchange | Metallurgical and Materials Transactions E (springer.com)

Rare Earth and Critical Element Chemistry of the Volcanic Ash-fall Parting in the Fire Clay Coal, Eastern Kentucky, USA. Jingjing Liu, Shifeng Dai, Debora Berti, Cortland F. Eble, Mengjun Dong, Yan Gao & James C. Hower. Clays and Clay Minerals. volume 71, pages309–339 (2023). Rare Earth and Critical Element Chemistry of the Volcanic Ash-fall Parting in the Fire Clay Coal, Eastern Kentucky, USA | Clays and Clay Minerals (springer.com)

A Study on Removal of Rare Earth Elements from U.S. Coal Byproducts by Ion Exchange. Peter L. Rozelle, Aditi B. Khadilkar, Nuerxida Pulati, Nari Soundarrajan, Mark S. Klima, Morgan M. Mosser, Charles E. Miller, and Sarma V. Pisapadi. A Study on Removal of Rare Earth Elements from U.S. Coal Byproducts by Ion Exchange | Metallurgical and Materials Transactions E (springer.com)

Little bacterium may make big impact on rare-earth processing. Phys.org. Blaine Friedlander. December 2023. Little bacterium may make big impact on rare-earth processing (msn.com)

US companies work to ramp up domestic rare earth manufacturing. Bret Baier and Amy Munneke. Fox News. December 6, 2023. US companies work to ramp up domestic rare earth manufacturing (msn.com)

Recovering Rare Earth Elements from Coal Mine Drainage Using Industrial Byproducts: Environmental and Economic Consequences. Marcos M. Miranda, Jeffrey M. Bielicki, Soomin Chun, and Chin-Min Cheng. Environmental Engineering Science. Vol. 39, No. 9. September 15, 2022. Recovering Rare Earth Elements from Coal Mine Drainage Using Industrial Byproducts: Environmental and Economic Consequences | Environmental Engineering Science (liebertpub.com)

Coal refuse. Wikipedia. Coal refuse - Wikipedia

The Remarkable Responsibility of Coal Refuse Power. Sonal Patel. Power Magazine. August 2, 2021. The Remarkable Responsibility of Coal Refuse Power (powermag.com)

Rare Earth Element Trap-Extract-Precipitate (REE-TEP) Process. The Ohio State University. Office of Innovation and Economic Development. 2022. Rare Earth Element Trap-Extract-Precipitate (REE-TEP) Process | Office of Innovation and Economic Development, The Ohio State University (osu.edu)

From pollutant to resource: WVU scientists push rare earth element technologies closer to production. WVU Today, April 21, 2021. From pollutant to resource: WVU scientists push rare earth element technologies closer to production | WVU Today | West Virginia University

Rare earth elements from coal mining could boost Appalachian region. Mark Cutis. 13WOWK. July 25, 2019. Rare earth elements from coal mining could boost Appalachian region | West Virginia Water Research Institute | West Virginia University (wvu.edu)

WVU awarded $5 million to continue rare earth project, build acid mine drainage treatment facility. WVU. October 2, 2019. WVU awarded $5 million to continue rare earth project, build acid mine drainage treatment facility | West Virginia Water Research Institute | West Virginia University

Polluted Streams May Yield Minerals Critical for High Tech. Steve Baragona. Voice of America. December 5, 2019. Polluted Streams May Yield Minerals Critical for High Tech | West Virginia Water Research Institute | West Virginia University (wvu.edu)

Turning coal mine drainage into source of rare minerals. Tatyana Woodall. Ohio State University. Phys.org. January 3, 2023. Turning coal mine drainage into source of rare minerals (phys.org)

China bans export of rare earths processing tech over national security. Siyi Liu and Dominique Patton. Reuters. December 22, 2023. China bans export of rare earths processing tech over national security | Reuters

Acid Mine Drainage Treatment Solutions. WesTech. Acid Mine Drainage Solutions for the Mineral Industry (westech-inc.com)

WVU partners with Extreme Endeavors to mine rare earth elements from acid mine drainage. Veronica Ogbe. WDTV. July 13, 2020. WVU partners with Extreme Endeavors to mine rare earth elements from acid mine drainage | West Virginia Water Research Institute | West Virginia University

WVU researchers move rare earth elements technologies closer to production. Tracy Novak. WVU Energy Institute. October 16, 2020. WVU researchers move rare earth elements technologies closer to production | West Virginia Water Research Institute | West Virginia University

From pollutant to resource: WVU scientists push rare earth element technologies closer to production. Jake Stump. WVU Today. April 23. 2021. From pollutant to resource: WVU scientists push rare earth element technologies closer to production | West Virginia Water Research Institute | West Virginia University

Water Research Institute director updates WV legislators on rare earth recovery efforts, urges law clarifying ownership. Mike Tony. Charleston Gazette-Mail. September 15, 2021. Water Research Institute director updates WV legislators on rare earth recovery efforts, urges law clarifying ownership | West Virginia Water Research Institute | West Virginia University (wvu.edu)

State lawmakers consider benefits, legal complexity of rare earth elements draft legislation. Mike Tony. Charleston Gazette-Mail. November 18, 2021. State lawmakers consider benefits, legal complexity of rare earth elements draft legislation | West Virginia Water Research Institute | West Virginia University (wvu.edu)

WV House passes bill clarifying who profits from extracting rare earth elements from mine drainage. Mike Tony. Charleston Gazette-Mail. February 7, 2022. WV House passes bill clarifying who profits from extracting rare earth elements from mine drainage | West Virginia Water Research Institute | West Virginia University (wvu.edu)

WV Senate passes bill clarifying who profits from extracting rare earth elements from mine drainage. Mike Tony. Charleston Gazette-Mail. March 11, 2022. WV Senate passes bill clarifying who profits from extracting rare earth elements from mine drainage | West Virginia Water Research Institute | West Virginia University (wvu.edu)

Could Coal Waste Be Used to Make Sustainable Batteries? Eliza Griswold. The New Yorker. August 26, 2023. Could Coal Waste Be Used to Make Sustainable Batteries? | West Virginia Water Research Institute | West Virginia University (wvu.edu)

West Virginia University From Pollutant to Product. Rockwell Automation. November 10, 2022. West Virginia University From Pollutant to Product | West Virginia Water Research Institute | West Virginia University (wvu.edu)

WVU’s Water Research Institute receives additional $11MM for Rare Earth Research. West Virginia Water Research Institute. September 13, 2023. WVU’s Water Research Institute receives additional $11MM for Rare Earth Research | West Virginia Water Research Institute | West Virginia University

Rare Earth Elements and Critical Minerals. NETL. 2021. Program-141_0.pdf (doe.gov)

Recovery of Rare Earth Elements and Critical Materials from Coal and Coal Byproducts: Report to Congress. May 2022. United States Department of Energy. Report to Congress on Recovery of Rare Earth Elements and Critical Minerals from Coal and Coal By-Products.pdf (energy.gov)

Isopach map and regional correlations of the Fire Clay tonstein, central Appalachian Basin. William F. Outerbridge. U.S. Geological Survey. Open-File Report 03-351. 2003. Isopach map of the Fire Clay tonstein, central Appalachian Basin (usgs.gov)

The Pennsylvanian Fire Clay tonstein of the Appalachian basin—Its distribution, biostratigraphy, and mineralogy: Discussion and reply. William F. Outerbridge. GSA Bulletin (1996) 108 (1): 120–125. The Pennsylvanian Fire Clay tonstein of the Appalachian basin—Its distribution, biostratigraphy, and mineralogy: Discussion and reply | GSA Bulletin | GeoScienceWorld

Distribution of rare earth elements in eastern Kentucky coals: Indicators of multiple modes of enrichment? James C. Hower, Cortland F. Eble, Shifeng Dai, and Harvey E. Belkin.  International Journal of Coal Geology. Volumes 160–161, 15 April 2016, Pages 73-81. Distribution of rare earth elements in eastern Kentucky coals: Indicators of multiple modes of enrichment? - ScienceDirect

Rare Earth and Critical Element Chemistry of the Volcanic Ash-fall Parting in the Fire Clay Coal, Eastern Kentucky, USA. Jingjing Liu, Shifeng Dai, Debora Berti, Cortland F. Eble, Mengjun Dong, Yan Gao & James C. Hower. Clays and Clay Minerals. Volume 71, pages 309–339, (2023). Rare Earth and Critical Element Chemistry of the Volcanic Ash-fall Parting in the Fire Clay Coal, Eastern Kentucky, USA | Clays and Clay Minerals (springer.com)

An Appalachian isochron: A kaolinized Carboniferous air-fall volcanic-ash deposit (tonstein). P.C. Lyons. Geological Society of America Bulletin. Volume 104, Issue 11. 1992. An Appalachian isochron: A kaolinized Carboniferous air-fall volcanic-ash deposit (tonstein) (usgs.gov)

Lanthanide, yttrium, and zirconium anomalies in the Fire Clay coal bed, Eastern Kentucky. James C Hower, Leslie Ruppert, and Cortland F. Eble. International Journal of Coal Geology 39(s 1–3):141–153. 1999. (PDF) Lanthanide, yttrium, and zirconium anomalies in the Fire Clay coal bed, Eastern Kentucky (researchgate.net)

Altered volcanic ashes in coal and coal-bearing sequences: A review of their nature and significance. Shifeng Dai, Colin R. Ward, Ian T. Graham, David French, James C. Hower, Lei Zhao, and Xibo Wang. Earth-Science Reviews. Volume 175, December 2017, Pages 44-74. Altered volcanic ashes in coal and coal-bearing sequences: A review of their nature and significance - ScienceDirect

The University of Kentucky Conducts Pilot-Scale Testing for REE Extraction and Recovery in NETL-Supported Initiative. DOE-NETL. February 16, 2021. The University of Kentucky Conducts Pilot-Scale Testing for REE Extraction and Recovery in NETL-Supported Initiative | netl.doe.gov

Rare earth elements (REEs) recovery from coal waste of the Western Kentucky No. 13 and Fire Clay Seams. Part I: Mineralogical characterization using SEM-EDS and TEM-EDS. Bin Ji, Qi Li, and Wencai Zhang. Fuel. Volume 307. January 1, 2022. Rare earth elements (REEs) recovery from coal waste of the Western Kentucky No. 13 and Fire Clay Seams. Part I: Mineralogical characterization using SEM-EDS and TEM-EDS - ScienceDirect

Rare earth elements (REEs) recovery from coal waste of the Western Kentucky No. 13 and Fire Clay seams. Part II: Re-investigation on the effect of calcination. Bin Ji, Qi Li, Honghu Tang, and Wencai Zhang. Fuel. Volume 315, May, 1 2022. Rare earth elements (REEs) recovery from coal waste of the Western Kentucky No. 13 and Fire Clay seams. Part II: Re-investigation on the effect of calcination - ScienceDirect

Operation and Process Control Development for a Pilot-Scale Leaching and Solvent Extraction Circuit Recovering Rare Earth Elements From Coal-Based Sources. Douglas Kweku Addo. Masters Thesis. Mining Engineering. University of Kentucky. 2019. OPERATION AND PROCESS CONTROL DEVELOPMENT FOR A PILOT-SCALE LEACHING AND SOLVENT EXTRACTION CIRCUIT RECOVERING RARE EARTH ELEMENTS FROM COAL-BASED SOURCES (uky.edu)

American Resources introduces new subsidiary American Rare Earth to extract metals in Kentucky. Proactive Investors. October 7, 2020. American Resources introduces new subsidiary American Rare Earth to extract metals in Kentucky (proactiveinvestors.com)

Four takeaways from Southwest Virginia’s critical mineral investigation. Charlie Paullin. Virginia Mercury.  August 8, 2023. Four takeaways from Southwest Virginia's critical mineral investigation - Virginia Mercury

National company acquires exclusive rights to Purdue rare-earth element innovations, critical for clean energy technologies. Purdue University News. February 2, 2021. National company acquires exclusive rights to Purdue rare-earth element innovations, critical for clean energy technologies - Purdue University News

Energy-Related Rare Earth Element Sources. Allan Kolker, Liliana Lefticariu, & Steven T. Anderson. Chapter Abstract in Rare Earth Metals and Minerals Industries. Springer. December 29, 2023. Energy-Related Rare Earth Element Sources | SpringerLink

Salt-loving bacterium can be genetically engineered to purify rare-earth metals. Keumars Afifi-Sabet. Live Science. January 10, 2024. Salt-loving bacterium can be genetically engineered to purify rare-earth metals (msn.com)

Mineralogy of a rare earth element-rich Manchester coal lithotype, Clay County, Kentucky. James C. Hower, Dali Qian, Nicolas J. Briot, Madison M. Hood, and Cortland F. Eble. International Journal of Coal Geology. Volume 220, 1 March 2020, 103413. Mineralogy of a rare earth element-rich Manchester coal lithotype, Clay County, Kentucky - ScienceDirect

Rare earth minerals in a “no tonstein” section of the Dean (Fire Clay) coal, Knox County, Kentucky. James C. Hower, Debora Berti, Michael F. Hochella, and Sarah M. Mardon. International Journal of Coal Geology 193 DOI:10.1016/j.coal.2018.05.001. Rare earth minerals in a “no tonstein” section of the Dean (Fire Clay) coal, Knox County, Kentucky | Request PDF (researchgate.net)

Critical Minerals Problems Need a Critical Minerals Solution: The Case for a Separate Regulatory Classification. Peter Cook and Seaver Wang. The Breakthrough Institute. January 26, 2024. Critical Minerals Problems Need a… | The Breakthrough Institute

H.R.2849 - Rare Earth Magnet Manufacturing Production Tax Credit Act of 2023. 118th Congress (2023-2024) | H.R.2849 - 118th Congress (2023-2024): Rare Earth Magnet Manufacturing Production Tax Credit Act of 2023 | Congress.gov | Library of Congress

Green Approach for Rare Earth Element (REE) Recovery from Coal Fly Ash. Pan Liu, Simin Zhao, Nan Xie, Lufeng Yang, Qian Wang, Yinghao Wen, Hailong Chen, and Yuanzhi Tang. Environ. Sci. Technol. 2023, 57, 13, 5414–5423. March 21, 2023. Green Approach for Rare Earth Element (REE) Recovery from Coal Fly Ash | Environmental Science & Technology (acs.org)

Environmental impacts of rare earth production. Petra Zapp, Andrea Schreiber, Josefne Marx, and Wilhelm Kuckshinrichs. MRS Bulletin. Volume 47, pages 267–275, (2022). March 2022. s43577-022-00286-6.pdf