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The relatively new concept of closure mining has given South Africa's struggling mining industry a new lease on life and potentially ensures the rehabilitation of our environment too. Sharon Davis tells us more.

Mining in South Africa began in earnest in the late 1800s and has been one of the pillars of our economy for more than a century. With the removal of the more easily accessible non-renewable underground minerals and resources, miners have had to mine at increasing depths, with a related increase in cost, to the point that mineral exploitation has become far less financially viable than it used to be.

Gold output peaked at around 1,000t in the 1970s and since then we have dropped from being the world's largest gold producer, down to fifth place. Once our economic mainstay, traditional mining as we know it, is on the decline.

We are still the largest producer of chrome, manganese and platinum, and amongst the top producers of coal, iron ore and several other important minerals, but the need to sink mine shafts to increasing depths of more than 3km underground makes mining in South Africa cost prohibitive and more akin to a sunset industry especially as far as gold and diamond mining is concerned.

Fortunately, a combination of three developments has breathed new life into our mining industry. Firstly, a decline in the strength of the Rand means mining companies earn more local currency for the minerals they extract - making mining, in general, more financially viable, at least while the exchange rate is depressed.

Secondly, new minerals that weren't worth the effort to extract some 60 years ago are now more in demand. And thirdly new technological developments have enabled mining companies to profitably extract smaller quantities, and lower grades, of minerals cost effectively.

This means that those ugly mounds of barren mine waste and the equally toxic dams of mine slurry, known collectively as mine dumps, or tailings, are being reprocessed and the land rehabilitated as the South African mining industry struggles to reinvent itself to suit the new circumstances it operates in.

Tailings reprocessing is the modern equivalent of the olden day gold rush, and while it is not exactly new, it is gaining traction and attention - and positive press because it has the win-win outcome of economic productivity and land rehabilitation.

JSE-listed Gold mining company, DRD Gold, provides a glittering example. They were one of the first South African companies to abandon traditional mining, which they did about six years ago, to focus on extracting gold from tailings.

New technology allows them to recover up to 40 percent of the gold left in particle form in tailings. By re-mining gold dumps in Johannesburg, DRD Gold extracted 33,600 ounces of gold, worth nearly US$40 million, in the last quarter of 2013 and the company plans to remove and treat more than 20 million tonnes of tailings from the hundreds of dumps around Johannesburg each year.

Mintails, an ASX-listed mine tailings processor, has recently developed new technology to process 350,000t of slimes from its extensive tailings resources. They expect to recover around 58kg in gold per month and have enough slime to reprocess until 2025.

Mintail's slimes reprocessing uses a new method to convert water affected by high concentrations of metals and other toxins as a result of traditional mining operations, known as acid mine drainage (AMD), into grey water which is safe for industrial use.

Goldfields has also developed new technology for a tailings retreatment plant and processes 12,000t of current tailings and 88,000t of old tailings per month - with an expected lifespan of six years.

DiamondCorp has also built a tailings retreatment plant with the capacity to treat 1,2-million tonnes of diamond tailings each year, and De Beers is recovering diamonds from its Kimberley tailings dumps and expects this to continue until 2023.

“There is enough minerals in closed mines and tailings to keep Zama Zamas, or illegal artisanal miners, going for more than a century. But there is also enough to keep industrialised mining going on a viable basis for another decade, or perhaps two, provided the closure mining business model is adopted,” says University of the Free State professor and trustee of the Water Stewardship Council, Antony Turton.

Traditional mining, over the last 120 years, was designed to extract minerals and pay dividends to off-shore shareholders and this has left a number of environmental problems that now act as constraints on future economic development, explains Turton.

AMD from large mine dumps is a persistent source of water pollution, and the 430,000t of uranium waste discarded during the mining process is limiting economic growth around Johannesburg, which is arguably the most uranium contaminated city in the world, he says.

Turton believes it is in South Africa's collective best interest to support the new mining business model with a focus on closure mining to both prolong the economic life of mines and preserve jobs threatened by traditional mine closures - and to rehabilitate the mine-impacted landscape to the point it can be safely used by society post closure.

The danger of not supporting and encouraging the closure mining model is that mining companies become unprofitable and close, or in the worst case, the mining industry fails, says Turton.

In either case: “All existing mine dumps will start to collapse as the machines used to maintain their shape are withdrawn. This will happen irrespective of liability for the dumps, as a bankrupt company has no assets to seize as a remedy.

“While environmental activists and politicians opposed to the traditional mining might see the collapse of the industry as a victory the unintended consequences will be the rapid deterioration of all mine-impacted ecosystems in the Witwatersrand Goldfields, exacerbating an existing AMD crisis into a national disaster,” says Turton.

While several opponents to traditional mining might like to see its immediate demise or transformation, closure mining does seem to be the rational choice, providing a potential win-win solution that doesn't leave the South African tax payer to cover the bill for the rehabilitation of mine dumps.

 

This article was first published in the Wits Business School Journal.