Industrial upscaling feasibility assessment and identification of key performance indicators for an in-situ bio-leaching project in narrow vein sulfide ores

Mining is fundamental to exploit an extensive range of products used in a variety of technologies in everyday life. As a result of their continuous extraction, most of the highly concentrated, superficial, and easily accessible ore deposits have been almost or entirely depleted by now. Moreover, to fulfill the needs and challenges of our society, such as green technology, renewable energies, microelectronics, and telecommunications, materials require a variety of specific elements whose global distribution is uneven and whose reserves in primary deposits are limited. These are known as “strategic elements,” and are defined by their high economic importance and vulnerability to supply disruption. Their exploitation is imperative; however, the extractive industry is nowadays facing new challenges, as our society becomes more environmentally conscious. The continuous and reliable supply of raw materials is currently affected by more complex mineralogy, lower grades, higher depths, and rigorous regulations. Moreover, the aim to reduce the environmental footprint and social impacts generated is crucial. Accordingly, conventional mining and processing methods are being highly criticized and constrained due to the large waste generation, energy consumption, and technical limitations imposed. Considering that the global trend is to move towards more sustainable development (SD), the industry’s obligation to improve conventional methods, develop new technologies, and in general, close the material loop becomes vital. Unfortunately, despite the recycling potential of these elements, new technologies, and government incentives, the recycling input rate is still not enough. For this reason, primary extraction not only will continue to be a part of the economy in the medium and long term, but also, strategic elements are not yet part of the circular economy (CE). Hence, CE principles and their implementation are starting to become more critical for the mining industry as a whole to abide by the SD requirements. Consequently, given the massive reserves of strategic metals in medium and low-grade ores, a promising way to deal with the previous issues could be applying alternative methods, such as bio-hydrometallurgy and in-situ leaching (ISL) technology. It transforms insoluble metals into an aqueous solution employing bacterial leaching; afterward, the metals are selectively separated by solvent extraction and further purified by electrolysis. Among the principal benefits, this process is advantageous, as it consists of mineral exploitation without primary waste production, that is, without rock extraction: a substantial waste reduction makes this technology valuable for present and future mining activities. To prove this idea, a framework to measure the mineral exploitation flows of mining methods based on material flow accounting (MFA) was developed and discussed in this paper. This framework is focused on CE principles and conservation of non-renewable resources. Therefore, a set of relevant material flow indicators for mining methods is implemented. Accordingly, for a defined deposit, in-situ bioleaching is compared to a conventional mining method, primarily in terms of productivity, the efficiency of recovery, and environmental impacts. Finally, the outcome of the analysis shows the benefits and disadvantages of each method related to the SD concept.