By Dr Bennet Thomas and Professor Sankar Bhattacharya, Monash University

Monash researchers are turning coal fly-ash into a new source of critical metals through a patented, low-impact extraction process.

The recent joint announcement by the Australian and US governments – the United States–Australia Framework for Securing of Supply in the Mining and Processing of Critical Minerals and Rare Earths – underscores the growing geopolitical importance of securing critical and rare earth metals. The signing of a historic bilateral framework, pledging a combined investment of US$8.5 billion into critical minerals pipeline projects, signals a strategic shift in global resource diplomacy.

Australia has long played a foundational role in this ecosystem, supplying high-grade rare earth minerals to global markets; however, while Australian miners undertake the complex and labour-intensive task of mineral extraction, the full economic and technological value of these resources is often realised offshore. A useful analogy might be preparing a gourmet meal: Australia sources the finest ingredients, hands them to an overseas chef, and then pays a premium to consume the final dish. This model raises fundamental questions about value retention and national benefit.

Currently, the industry understands that the bottleneck lies in onshore processing capabilities. While mining companies produce concentrates domestically, these are typically exported to countries with the technical expertise to refine them into high-purity rare earth metals. ‘Technical expertise’ in this context refers to the full spectrum of metallurgical capabilities – from mineral separation to final metallisation.

Moreover, the environmental implications of current processing methods are significant. The use of large volumes of inorganic acids and other harsh chemicals poses ecological risks, and the generation of radioactive by-products presents a serious challenge. These impacts are often felt most acutely by local communities, rather than urban populations. Consequently, rare earth processing is frequently outsourced to jurisdictions with more lenient environmental regulations.

At Monash University, driving sustainable change to build thriving communities is central to our Impact 2030 mission. In our research, we approached the rare earth metals challenge by asking a different set of questions – ones that go beyond conventional mineral extraction and processing paradigms.

Our investigation began with the characterisation of three coal fly-ash samples sourced from coal-fired power stations in Victoria, a state that holds one of the world’s largest reserves of brown coal. Decades of coal combustion have resulted in significant volumes of legacy waste, presenting both an environmental challenge and an opportunity. Our goal was to explore whether this abundant, low-cost, legacy waste stream could be reimagined to yield valuable products: specifically, globally critical rare earth elements.Through this research, we identified the potential to recover rare earth elements from coal fly-ash, reframing it not as waste, but as a strategic resource. Our analysis revealed that coal fly-ash samples contain approximately 500 milligrams per kilogram of rare earth metals, with certain sites, depending on the origin of the coal, showing enrichment levels as high as 1700 milligrams per kilogram. For context, low-grade rare earth ores typically contain around 1400 milligrams per kilogram, placing some fly-ash samples within commercially viable ranges. This discovery subsequently prompted a critical question: Can we challenge and transform the current state-of-the-art in processing such complex materials?

Coal fly-ash presents significant technical challenges due to its heterogeneous mineralogy. Historically, the extraction of rare earth elements from this material has relied on concentrated inorganic acids, raising both environmental and economic concerns. In response, our team engineered a novel process using environmentally benign solvents, achieving more than 95 per cent rare earth metal recovery – an unprecedented result in the field. This patented breakthrough, developed by us, represents a significant advancement in sustainable process engineering.

Initial laboratory-scale experiments at the 100-millilitre reaction level demonstrated high efficiency, prompting scale-up to a 30-litre system. Subsequent processing of the leachate under benign conditions has achieved 40–60 per cent separation of selected rare earth metals. The team is now finalising the engineering design for continuous operations at the 100-litre scale, with plans underway to construct a demonstration facility at Monash University. This milestone will enable robust techno-economic analysis and mark a critical step towards commercialisation.

This brings us to a pivotal question: Where to from here? The path forward lies in translating laboratory-scale research into commercially viable business models that can navigate the complex landscape of venture capital, mining industry partnerships and government-backed funding. Australia is not alone in this race; global competitors are advancing rapidly, producing critical materials to independently strengthen national resilience amid growing economic and geopolitical uncertainty.

This patented work has catalysed broader research into other waste streams, including red mud, electronic waste, mine tailings, battery waste, and end-of-life electrochemical devices such as electrolysers and fuel cells in our laboratory.

Our work aims to not only diversify Australia’s critical metals supply chain, but to do so in an environmentally sustainable manner. By reducing chemical intensity and enhancing onshore value retention, our approach aligns with the Australian Government’s commitment to climate action and circular economy innovation.

To remain competitive, Australia must accelerate its innovation pipeline and build a robust ecosystem that supports the entire value chain of critical minerals – from resource extraction to refined product. This requires coordinated investment in advanced processing technologies, sustainable engineering solutions and strategic engagement across sectors. By doing so, Australia can position itself not only as a resource-rich nation, but also as a global leader in sustainable resource innovation.