NETL work to discover and develop efficient ways to recover rare earth elements (REEs) from coal wastes like acid mine drainage (AMD) and fly ash includes intensive in-house research and more than 40 project partnerships with the private sector and higher education research institutions throughout the United States. Demonstration projects are setting the stage for the next phase of the effort to establish a domestic supply chain of REEs that supports the nation’s economic growth and deployment of clean energy technologies. A secure source of REEs also reduces our reliance on foreign sources and increases national security.

NETL researchers have been working to find ways to harvest those REEs from AMD — water from abandoned carbon ore mines and active mining that flows over or through sulfur-bearing materials, forming acidic solutions. This AMD is currently the main pollutant of surface water in the mid-Atlantic region. AMD-containing waters require remediation throughout Appalachia using various treatment processes, including one that sends mine water through a limestone bed. This passive remediation method causes metals to drop out of the solution and cleans the water prior to discharge. The limestone beds are then dredged and secured in a landfill or buried along with recoverable amounts of REEs.

Christina Lopano, Ph.D., a research physical scientist who received the Secretary of Energy’s Excellence Award for her work to recover REEs from coal waste streams such as fly ash and AMD, explained that REE’s are essential to the energy, defense, medical and consumer technology manufacturing industries.

“Supply and access to those elements are critical for the U.S. economy,” she said. “However, a majority of the world’s REE sources and manufacturing are controlled by other countries, which is why NETL is pursuing alternative sources closer to home. Work funded by NETL identified acid mine drainage from prior and current mining operations, as potential sources of REEs and other critical minerals.”

In 2014, DOE ‘s Office of Fossil Energy and Carbon Management (FECM) and NETL undertook the mission of expanding the nation’s supply of REEs, with an initial focus placed on addressing the feasibility of extracting, separating, recovering and purifying these materials from carbon ore-based resources.

For NETL, that meant conducting intensive internal research to understand how REEs are present in various materials and to what extent they can be separated and recovered. Researchers used a range of resources like classic X-ray diffraction, scanning electron microscopy and microprobe analyses, and cutting-edge analytic characterization techniques to develop novel extraction techniques. Through that effort NETL identified promising domestic REE-containing coal-based resources and demonstrated the production of high-purity REEs in bench- and small pilot-scale facilities.

The objectives of the DOE-NETL program from 2014-2020 were to:

• Recover REEs from coal and coal byproduct streams, such as run-of-mine coal, coal refuse, clay/sandstone over/under-burden materials, power generation ash, and aqueous effluents as acid mine drainage.
• Advance existing and/or develop new, second-generation or transformational extraction and separation technologies to improve process system economics and reduce the environmental impact of the coal-based REE value and supply chain.
• Initiate efforts for the reduction of rare earth oxides to rare earth metals (REMs).

To achieve the mission goals, research was conducted through proposal projects and other DOE national labs including the Los Alamos National Laboratory, Lawrence Livermore National Laboratory, Idaho National Laboratory, and Pacific Northwest National Laboratory. Similarly, collaborative RD&D projects were conducted with industrial stakeholders and numerous universities.

Since 2016, numerous extramural stakeholder extraction separation and recovery processing approaches have been identified and used to demonstrate the technical feasibility of extracting REEs from coal, coal refuse, power generation ash and AMD. By 2020, these efforts resulted in the design, construction and operation of three first-of-a-kind, small pilot-scale facilities. 

• In 2018, the University of Kentucky produced small quantities of pure mixed rare earth oxides (MREOs) in a modular pilot-scale facility, from coal refuse materials from the Central Appalachian and Illinois Coal Basins. Forty-five percent of the critical elements in the University of Kentucky’s REE concentrate are used in national defense technologies and the high-tech and renewable energy industries. In 2020, 98% pure MREO concentrates were produced with co-production of CMs.
• Commissioned in July 2018, West Virginia University’s bench/small pilot-scale REE extraction facility began producing REE pre-concentrates from AMD and sludge materials from the Appalachian Coal Basin. By 2019, WVU produced approximately 80wt% (800,000 ppm) pure MREO concentrate, and in 2020, WVU succeeded in producing approximately 98wt% (980,000 ppm) pure MREO concentrates from AMD with co-production of CMs.
• In July 2018, Physical Sciences Inc., produced greater than 15wt% (150,000 ppm) MREOs in its micro-pilot facility in Andover, Massachusetts, using post-combustion ash that was generated in a Power Plant boiler that burns East Kentucky Fire Clay coal. PSI used the micro-pilot facility to develop the design and operating parameters to scale its process to the pilot-scale operating system with Winner Water Services in Sharon, Pennsylvania. The PSI-Winner Water pilot-scale facility became operational in November 2019.
• In 2019, the University of North Dakota demonstrated the capability of producing a 65wt% (650,000 ppm) MREO concentrate from lignite in its bench-scale facility using a one-step selective mineral acid leaching process. 

By creating a sustainable domestic REE and CM supply chain, the U.S. would reduce its risk of supply disruption for essential domestic and military industries, would have the potential to produce intermediate products and manufacture end-use products onshore, which are currently valued above $1.2-trillion, and would prevent the U.S. from being left behind in the emerging clean energy technology market. 

NETL’s REE and CM program has demonstrated the first step towards national independence from reliance on offshore REE and CM suppliers through its RD&D efforts using coal-based resources to produce small quantities of high purity MREOs and CMs. Leveraging accelerated production of these materials in engineering-scale prototype, demonstration and commercial facilities, in parallel with the return of onshore component manufacturing, will facilitate not only self-reliance but also Made in America across numerous critical clean energy and defense product lines and supply chain markets.

NETL is a DOE national laboratory that drives innovation and delivers technological solutions for an environmentally sustainable and prosperous energy future. By leveraging its world-class talent and research facilities, NETL is ensuring affordable, abundant and reliable energy that drives a robust economy and national security, while developing technologies to manage carbon across the full life cycle, enabling environmental sustainability for all Americans.