In situ pilot-scale demonstration of a novel mineral processing biotechnology for recovering metals from lateritic ores (International)

Nickel and cobalt are two key metals used by modern civilization in a host of applications. Cobalt, in particular, is categorized as a "strategic metal" in view of its great importance to the development of "green technologies" (such as energy storage in batteries used, for example in new generation electric and hybrid vehicles) and also because of the fact that much of its production is concentrated in parts of the world perceived to be potentially unstable. Most of the nickel and cobalt produced from mining primary ores originates from reduced (sulfidic) minerals, though the bulk of accessible global reserves of nickel (in particular) is contained in oxidized ores, most notably laterites, which are widely distributed throughout (mostly) tropical regions. Although technologies exist for extracting valuable metals from lateritic ores, these mostly operate at high temperatures and pressures and are therefore highly energy consuming and have large carbon footprints. Recently, a microbiological mechanism for extracting nickel and cobalt from limonitic laterites, which operates at atmospheric pressure and ambient (30 - 40C) temperatures has been described and demonstrated at laboratory scale. Biomining is often considered to be a "green" approach for obtaining metals, and has been used for over 50 years to obtain copper. The novel technology developed at Bangor University in conjunction with the mining industry has greatly extended the range of metal ores that can be bioprocessed. Limonitic ores from mines located in different parts of the world (including Asia, Africa and South America) have been trialed in the frame of a current NERC-sponsored project (which focuses specifically on cobalt) and all have been shown to be amenable to bioprocessing using this new approach (referred to as "reductive mineral dissolution"). Among these was material from a new mining enterprise in Brazil, located in Piaui state, the owners of which are active members of the NERC project consortium. The Piaui mine has not yet become a full-scale operation, and the bioprocessing option has several perceived major advantages of what is currently envisaged as the operating protocol (leaching with concentrated sulfuric acid in heaps). These include: (i) eliminating the need to transport in large amounts of concentrated acid to the remote mine site (both costly and hazardous); (ii) removing the need to purchase an acid-generating plant for long-term sulfuric acid generation (the cost of which is equivalent to ~25% of the total capital cost of the mine); (iii) the potential to enhance both rates and extents of metal extraction from the ore. The original reductive mineral dissolution protocol has been fine-tuned in the current NERC project to minimize or eliminate the need to use acid to neutralize the alkalinity generated when minerals in the limonite ores dissolve. Instead the acid is generated in situ from elemental sulfur by specialized bacteria. There is a perfectly timed opportunity to scale up the reductive mineral dissolution approach from laboratory to pilot scale, and this is greatly facilitated by the fact that large columns required for this are already in place at the Piaui mine site. The project will involve firstly producing sulfur colonized by the specialized bacteria used in the process, shipping this from the UK to the mine at Piaui where it will be combined with the ore (and additional sulfur) and packed into a large (4 m high) column. This, and a control (acid-leached) column will be operated in re-circulation flow mode for 6-7 months, by which time most of the metals will have been extracted. The columns will then be dis-assembled and, if results are as anticipated, used for the next stage in the process (heap leaching; beyond the scope of the current project). This demonstration plant will provide essential data that will help promote the application of this novel biomining approach to laterite mines throughout the world.

The products of the biotechnology being developed within this project are two base metals, nickel and cobalt, both of which are vital to modern civilization and the global economy. Recent projections of a Ni market of ~19.4 million (metric) tonnes in 2017 and an average price of ~$ (US) 9,000/tonne translates to an annual value of ~ £13.5 billion for this commodity. The global demand for, and production of, cobalt is much less than that of nickel (~100,000 tonnes/annum) though its value is far greater (~$ (US) 59,000/tonne) which translates to an annual value of ~ £4.6 billion for this commodity. The combined annual value of these metals combined is therefore ~ £18 billion. Over 40% of cobalt is currently used in production of batteries, notably for use in electric and hybrid vehicles. Technologies, such as that used in the current project, which expand the range of primary ores from which Co (and Ni) can be extracted will reduce these risks, by (i) facilitating greater metal production using an environmentally-benign approach and (ii) expanding the potential for Co production in countries located in tropical areas where lateritic ores are mostly located (e.g. within South America and the Caribbean, Africa, Australia, and Asian countries such as Indonesia) as well as Greece, Turkey and other countries located closer to the UK. Bio-processing of lateritic ores will obviously need to establish from a zero base (its current status) but has the potential to become a major factor in production of these metals (as has been the case for copper and gold in conventional biomining). Assuming that the "bio" production could contribute from 1 to 5% of Ni and Co production within the next decade, this equates to a combined global market worth between ~£200 - 900 million. (These are not unrealistic figures bearing in mind that biomining is thought to account for between 10 and 20% of current copper production).
There are many potential net beneficiaries, therefore, of this project. The most immediate of these are owners of lateritic mines, which are mostly located in tropical (often poorer) countries, though there are some closer to the UK, e.g. in Greece and Turkey. The pilot-plant to be commissioned has the potential to demonstrate that an energy-lean biotechnology can be used to extract metals from oxidized lateritic ores. This would be the first demonstration of its kind in the world, and would herald a significant change in direction for future mining - one with far greater "green" credentials. Apart from the owners of laterite mines, downstream users of nickel and cobalt would benefit from having a much more diverse and therefore secure supply route of these metals. This is particularly of current concern for manufacturers who rely on ongoing availability of cobalt (and at a price that does not make their products uneconomical). Finally, there are not benefits for the planet as a whole. Beyond this, any new technology used in mining metals that reduces energy use and lowers carbon emissions will directly benefit the entire population of the world. The environmental benefit is further enhanced by the fact that both metals are used in technologies and applications that will also reduce emissions of greenhouse gases, e.g. cobalt, which is currently vital for production of new generation, environmentally-benign electric and hybrid vehicles.