Critical raw materials are essential for achieving the energy transition needed to meet climate targets using renewable energy technologies. However, producing more green technologies requires at least 4-5 times more mineral usage, which raises some concerns, such as reserve restrictions and supply chain risks associated with extracting these minerals. This is because governments and some companies have conducted studies to investigate more options for recovering critical raw materials opportunities from the mine wastes, as mentioned in the previous blogs.
Speaking about coal, which turns into ash when it burns, always seems like a significant environmental problem. However, coal and coal sludge contain substantial amounts of critical raw materials such as rare earth elements, cobalt, and manganese. The challenge is to find ways to turn this waste into a valuable resource. Penn State’s researchers have been evaluating rare elements in coal by-products. Recovering these minerals from the waste stream contributes to developing strategies to address the critical issue of the supply chain gap that most countries face.
Rare earth elements, although not rare, are limited in their concentrated deposits, which makes their extraction uneconomical. These elements have unique properties that set them apart from other metals, and as a result, they are used in various industries such as energy, defense, military, smartphones, electric vehicles and etc. They are also used as an additive in the glass industry to give glass optical properties or for tasks such as polishing glass. These elements have become increasingly widespread in the production of magnets, with neodymium-iron-boron magnets being the most vital magnet type. These magnets are handy when there are restrictions in terms of space and weight. Additionally, anodes made of lanthanum-based alloys are employed in nickel-metal hydride batteries. Considering reserve and supply chain network, China currently leads the world in rare earth element production, accounting for over 90% of supply in the last ten years. However, concerns about capturing these resources and managing environmental impact have increased rare earth element production worldwide, such as Mount Weld in Western Australia. Further development projects are still ongoing. The world has also been exploring ways to recover these elements as secondary materials from different old mines.
In some places, like Pennsylvania, coal waste streams have such potential value that they are worth exploring since, over millions of years of coal formation, some valuable heavy metals may have precipitated into the clay layer beneath peat bogs. Considering the acid mine drainage from the abandoned coal mines and holds in the sludge treatment ponds, coal waste dumps and coal ash existing with the coal power plants might be a potential resource to find rare earth elements. This study has evaluated where these critical minerals are and their concentrations. To do this, researchers have benefited from the history of mining data, confirmed its accuracy in the field, and developed an enrichment process for recovering critical minerals from acid mine drainage. As a result, they have mentioned that for only rare earth elements, this process can recover 85% of rare earth elements from acid mine drainage and sludge ponds. Another study in Johannesburg has shown that the total rare earth elements content from discant and standard coal mines was above 225 ppm, which is sharply above the cut-off grade of 133 ppm for extracting REE in the coal. Briefly, more than 30 projects have been conducted in the USA to secure potential REE production from coal and its waste streams. At the same time, the researchers still need to prove that the process is economically valuable. This makes sense since extracting critical raw materials, especially rare earth elements, from coal waste, sludge ponds and acid mine drainage is much more inexpensive than extracting them from mineral ores. These findings are promising and could be implemented in another geographic area to benefit the coal waste in the concept of the energy transition. For instance, consider Scotland cause there were several coal mines run there between the nineteenth and early twentieth centuries. So, could there be any opportunities to recover these minerals from coal or coal waste in Scotland? A sure thing.
Another fact is that, according to EURARE, the most critical REE existence in the British Isles is in North Scotland. Veins of hydrothermally altered mafic syenite, which are abundant in allanite and apatite, can be found in the Loch Loyal syenite complex. The veins can contain up to 2 wt per cent of rare earth oxides. REE-bearing minerals like fergusonite and gadolinite occur in various complexes. These minerals are particularly abundant in the Northern Arran granite in Scotland and the Mourne Mountains of Northern Ireland. Alluvial sediments derived from the granites have locally concentrated REE minerals in these areas. By examining the coal field map and REE mineralization, it becomes evident that the two have a a correlation.
If understood correctly, this correlation could lead to invaluable insights and opportunities. Let’s explore this connection further to uncover the untapped potential.
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