Dirty gold: The seamier side of mining

Nature | Brian Owens

March 14, 2013
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Gold mining can be a dirty business, both environmentally and ethically. Extracting gold from the mined ore creates a huge amount of waste — roughly 20 tonnes of mining waste to make a single 18-carat ring containing less than 10 grams of gold, according to an estimate from Earthworks, an environmental watchdog based in Washington, DC. What's more, many small-scale operations in the developing world make use of child labour, and can support civil wars or local warlords.

The US Environmental Protection Agency rates the metal mining industry as the number one toxic polluter in the country in its Toxics Release Inventory 2011. A large part of this pollution is cyanide, the main chemical used to leach gold from crushed ore; it can contaminate surface and ground water if it leaks from waste sites. One of the worst such accidents occurred in Romania in 2000, when a burst dam sent cyanide-contaminated water into the Someş river, and eventually into the Danube. It killed large numbers of fish and poisoned the drinking water of more than 2.5 million people.

Mining companies often say that new technologies will make mining cleaner, says Alan Septoff, communications director at Earthworks, but that is rarely the case. Research commissioned by Earthworks found that, in the United States, “75% of mines wind up polluting water, no matter what they promise,” he says.

This is at least partly because nothing is quite as effective as cyanide at getting gold out of rock. There have been attempts to find less dangerous chemicals, but they have been largely unsuccessful, says John Monhemius, a mineral engineer at Imperial College London. Thiosulphate, thiocyanate, perchlorate, chloride and bromine have all been tried, but none can match cyanide's specificity for gold.

“I did quite a lot of work on thiocyanate, but in the end I decided it wasn't any better than cyanide,” Monhemius says. Although it is not as directly poisonous as cyanide, thiocyanate requires much higher concentrations so the results of an accidental spill would be just as bad — possibly even worse, he says. “Cyanide suffers from a lot of bad press,” Monhemius adds. “If it is used properly, it doesn't cause a threat to the environment.”

The gold mining industry's voluntary International Cyanide Management Code provides guidelines to ensure the chemical is manufactured, transported and used safely.

Unwanted neighbour

Gold mines can be a source of great wealth but they are not always welcomed by the local population. In Peru, for example, massive protests and nationwide strikes against the planned Conga gold mine eventually led to the suspension — although not the cancellation — of the project in 2012. People were concerned that the amount of water the mine would use would endanger agricultural and drinking water supplies in the region.

Earthworks is running a campaign called No Dirty Gold, which aims to encourage consumers to pressure the mining industry to be more environmentally and socially responsible. The industry is engaging with Earthworks and other civil society groups, says Septoff, although the two sides have not yet agreed on what “responsible mining” should look like.

In October 2012, the mining industry issued a Conflict-free Gold Standard that companies can use to certify that none of the proceeds of their gold — including any bought from local small-scale operations — is supporting “unlawful armed conflict”. The first public announcements by companies that they are complying with it, which must be externally verified, are expected in early 2014 when they report on their 2013 activities.

Gold not green

But even avoiding mining by recycling gold from scrap electronics is not always the ethical or environmentally friendly option. Although advanced plants, such as precious-metal recycling firm Umicore's closed-loop facility in Hoboken, Belgium, release very little waste, this standard is not universally followed. In fact, much electronic waste is sent to the developing world, where piles of televisions and computers are burnt under the open sky, with cyanide poured over the slag to extract the precious metals. This not only releases dangerous fumes and chemicals, but also results in low yields.

“It is obvious that from an environmental and social point of view this unregulated recycling is a disaster,” says Umicore recycling engineer Christian Hagelüken. The electronics recycling industry must be better managed and regulated, he says, to stop dangerous and wasteful operations. — B.O.

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