Fat谋ma Yavuz
The mining sector, by its very nature, is characterized by a multifaceted and complex structure that necessitates in-depth knowledge and an interdisciplinary approach. The success of an investment decision cannot be reduced to a single variable; therefore, it is essential that geological, geophysical and environmental factors are evaluated as a whole in feasibility studies. While the structure and chemical composition of the ore and the geophysical properties of the rock are key determinants, external factors such as the location of the mining site, harsh climatic conditions, and the socio-economic structure of the region also play a critical role in determining the direction of the investment. This comprehensive analysis provides the foundation for the development of mineral recovery processes that are able to address these structural challenges.
Whilst the primary objective in process development is to achieve maximum economic efficiency and yield, there is also a concurrent emphasis on environmental standards and the utilization of the least toxic chemicals. As is the case in other chemical industry processes, achieving a zero-waste target in mining processes is not practically feasible by nature. However, minimising environmental impact is the sector’s most important agenda item. Moreover, it is imperative to recognize that the generation of mining waste can be significantly reduced or even prevented by optimizing mineral extraction and processing processes. This optimization process entails the development of novel knowledge and technologies with the objective of enhancing waste recycling and resource recovery, with a particular focus on the ore being processed.
The graph showing the trend in the number of active metal mines in the US from 1983 to 2023 indicates significant consolidation in the sector.
During this period, the number of active mines fell from 900 to below 300, representing a decrease of approximately two-thirds. This sharp decline resulted in the closure of hundreds of small and inefficient mines, with the sector focusing on fewer but larger, more efficient, and technologically advanced operations. However, this decrease in the number of mines does not mean that the sector has shrunk entirely. On the contrary, the tailings left behind by these closed underground and surface mines have created a massive secondary source reserve of valuable metals that were previously abandoned because they were economically or technologically inaccessible. Today, thanks to increasing global metal demand and advanced recovery technologies (such as advanced leaching and biometallurgy), these old waste piles are seen as new, high-value and economically profitable mineral deposits. Therefore, the downward trend in the graph represents not the end of an era, but rather the beginning of the sector’s potential transition to a circular economy through the reprocessing of mining waste. This transformation not only ensures the recovery of critical raw materials, but also contributes significantly to reducing environmental risks (such as acid drainage) at abandoned sites.
Evaluation of Mine Waste as a New Resource
The metal production process consists of three main stages: ore enrichment (separation of minerals from gangue), extractive metallurgy (pyrometallurgy, electrometallurgy, hydrometallurgy), and refining. These industrial processes and mining activities produce significant amounts of mining waste, which is grouped into two main categories: waste rock and tailings. Waste disposal is typically carried out through landfilling (tailings ponds), underground backfilling, deep water disposal, or recycling methods. In the past, due to technological limitations and the availability of richer ore deposits, low-concentration minerals were left behind in large waste piles. However, today, the general decline in ore quality in new mines, the steady rise in metal prices, and the increasing need for resources have made these old waste piles economically attractive sources of raw materials. Critical raw materials, such as battery metals (cobalt, lithium, nickel) and rare earth elements (REE), in addition to traditional metals like copper, gold, and zinc, are being recovered from these wastes in order to increase the diversity of sources beyond primary production (active mines).
The demand for these elements has increased significantly over the past decade due to their need for high-technology equipment, such as low-carbon energy machinery, auto catalysts, and digital technologies. The reprocessing of waste piles not only provides economic profitability but also fulfills a critical environmental mission. This process significantly helps reduce the environmental impacts and risks of old mining sites, particularly long-term problems such as acid mine drainage (AMD), by removing or stabilizing toxic elements (arsenic, mercury, sulfur) found in waste.
The Key to Investment: Detailed Characterization and Scalable Validation
The key to achieving high efficiency and economic profitability in recovering valuable metals from mining waste lies in avoiding a one-size-fits-all approach and meticulously tailoring processes to the unique characteristics of the waste. This critical process consists of detailed waste characterization, customized pre-treatment and leaching system selection, and the integration of recovery technologies suitable for the targeted metal mixture.聽 In this context, the most important consideration for mining companies and investors contemplating investment in this area is this: Process success is determined not at the table, but in the laboratory and pilot plant. Any recovery project promising high yield and low operating costs necessitates a comprehensive research and development (R&D) process. The detailed characterization of the waste requires determining not only the valuable metal content, but also which minerals those metals are associated with, the particle size, and any inhibiting impurities (carbonates, clays, etc.) that will consume the leaching reagents or reduce the yield.
This comprehensive analysis provides a roadmap for selecting the mechanical pre-treatment (grinding), chemical pre-treatment (bio-oxidation, etc.), and leaching system (reagent, duration, temperature). It is essential that this theoretical approach be rigorously verified on a laboratory scale. The most efficient and least environmentally damaging leaching conditions (e.g., selective recovery systems from the leaching solution) are determined at this stage to ensure maximum metal dissolution and minimum reagent consumption. Finally, establishing a suitable pilot plant is vital for accurately determining economic feasibility and operational risk. The pilot plant demonstrates how well the optimal conditions determined in the laboratory perform at actual industrial scale, minimizes scale-up risks, and ensures long-term profitability. Transforming mining waste from merely an environmental burden into a real asset that extends the operational life of companies, generates additional revenue, and supports sustainability is only possible through this meticulous four-stage customization process. Therefore, investment decisions in this area depend on pioneering investments in comprehensive R&D, detailed characterization, and pilot plant validation. This is the only way to guarantee not only efficiency but also long-term economic profitability.