The importance of mineral processing in the quest for a circular economy

Sustainable Minerals '18 has the tag “Towards a circular economy”, and in opening the conference this morning, after thanking our corporate sponsors Outotec and Zeiss, I spoke about the crucial role that mineral processing and extractive metallurgy will have in this quest. 

With a world population of 7.6 billion, sustaining our way of life is becoming a major issue, but it is not widely acknowledged that a sustainable society is very much dependent on a sustainable mining industry. The perception with many is that the mining industry is a dangerous, dirty business run by capitalists intent only on self-gain at the expense of the environment. The reality is that society could not exist without a thriving mining industry; it is the great feeder which allows all other industries to operate.

Mining never gets easier, the tonnages mined steadily increase while the available ores become ever leaner and complex, so in order for the industry to be sustainable it must continually adapt to these changes and innovate.

No better example of the need to innovate can be found than by looking at the state of the industry at the beginning of last century, when increasing industrialisation had led to a rapid rise in the demand for metals, particularly the base metals such as copper. The widespread use of electricity at the end of the 19th century vastly inflated the demand for the red metal and the high grade ores, of which Cornwall had been the biggest supplier, soon became depleted. Attention then turned to the vast quantities of low grade base metal ores in Australia and the Americas. 

However, as the only option for recovering the metals from these ores was smelting, it was necessary to upgrade them for economic extraction, and the only methods available were hand sorting and simple gravity concentration processes, totally inadequate on these low grade finely disseminated deposits.

The mining industry was in a crisis, and so was the new industrialised world which was reliant on these metals. The search was on for a means of concentrating these ores, and the saviour of the industry was froth flotation, often described as the most important technological development since the discovery of smelting.

Froth flotation is now the mainstay of the mining industry, and there are few mines in the world which do not use it somewhere in the flowsheet. It is true to say that without it the base metals would be regarded as precious metals, and we would live in a very different civilisation.

One metal which we now take for granted, and was indeed a precious metal in the late 19th century, is aluminium, which was more precious than gold although it was well known that it had potential as a light, strong metal which would not corrode, due to its passive oxide layer. No one of sound mind would have predicted that aluminium would one day be a cheap metal in global use for common household utensils, the invention of the Bayer and Hall-Héroult processes allowing the economic mass processing of bauxite ores. At around the same time cyanidation of gold ores was invented, these processes marking the birth of modern hydrometallurgy, which has seen many innovations in the 20th Century, with the continuing development of leaching and bioleaching, solvent extraction and ion-exchange.

A century later what are the big challenges now facing the industry in order to sustain ever increasing demand for metals and minerals, which will be influenced in a major way by the electric vehicle revolution? There will be a massive boom in metal mining as electric replaces the internal combustion engine, and copper, nickel, lithium and cobalt should particularly benefit (as well as non-metals such as graphite). According to Glencore, a typical electric car would need about 160kg of copper, 11kg of cobalt and 11kg of nickel.

It must be remembered that ores are finite resources, so there will be an increasing strain on primary sources, and a concomitant increase in energy and water requirements. Critical to a sustainable future, however, is the need to move from a linear to a circular economy, by retreating old tailings dumps and crucially by recycling materials at the end of their effective lives.

Recycling is viewed by many as the panacea of sustainability. Once an article has reached the end of its useful life, you take it to a municipal waste centre, and it is recycled for further use. This is fine for products made from a single material such as glass, which can be melted down and reused, or for certain metals which are used in their native form, such as copper and lead. However when metals are alloyed with other metals or non-metals, recycling becomes much more challenging and if the metals and other elements are in tiny amounts in a device, then the problem becomes even more complex. Perhaps the greatest recycling challenge is that of recovering metals from waste electrical and electronic equipment (WEEE) and other complex high-tech products. Some of these metals, such as germanium and gallium, are dependent on their primary production on base metal mining, from which they are by-products. Indium, now critical to our modern lifestyle, is the most important ingredient, as an indium-tin oxide, in the production of ubiquitous touch screens. Indium is produced in small amounts from the mining of Zn ores, and the sheer number of smart phones, tablets etc. produced each year requires around 700 tonnes per year of indium. Recent estimates however, suggest that total reserves are around 16,000 tonnes, so it is a very finite resource, and great efforts are being made to recycle it.

So there are great challenges ahead and mineral processing will be at the forefront of the future quest for a circular economy, which is why this conference series is so important, not only to the mining industry, but to society in general.

My opening remarks preceded a full day of 14 presentations, beginning with Rob Dunne's keynote "Water- crisis, conflict, resolution?".

And at the end of a long day, what better way to relax than with drinks at the evening sundowner overlooking the Country Club's impressive golf course.

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