Zero Water, Zero CO2
Two companies are piloting projects aimed at creating the perfect clean mine, using zero freshwater and releasing zero CO2. If they succeed, the industry may be close to building its first footprint-free operation:
A large, green slab of metal arrived at the Penasquito gold mine in Mexico last year. Mud-splattered trucks drive onto the slab, are scanned by sensors, then blasted by water at 520 gallons per minute, dislodging dirt and debris without using any soap. 100 per cent of the water is caught, cleaned and used again.
The machine was bought by the mine's owner, Vancouver-based Goldcorp, which launched an “H2Zero” initiative two years ago, shortly after appointing a new chief executive, David Garofalo. The “moonshot” objective, he said at the time, was to create a mine that uses no freshwater.
The mining industry uses 7 to 9 cubic kilometres of water every year, according to ICMM, an industry body, the bulk of it drawn from groundwater. That is fine in water-rich countries, such as Canada, but problematic in water-strained countries, such as Mongolia, Mexico or Chile, where an estimated 12 tonnes of freshwater is used per tonne of copper produced.
Penasquito is sitting on 11 million ounces of gold, worth around $15bn at prices today, but is in a semi-desert environment in one of the poorest parts of Mexico, where most jobs are reliant on agriculture.
Goldcorp is re-engineering every aspect of water use at the mine, from how it washes vehicles to how it handles waste. Large mines typically create huge ponds of slurry that are 75 per cent water, but by squeezing that figure down to 15 per cent, Penasquito will instead churn-out “dry stacks” of rock, cutting out the cost of building dams. It is also engineering some of the world's most advanced water filters, made of carbon fibre and five metres wide, lowering its recycling costs from $3 to $2 per tonne.
“The current generation of mines are intensive across a number of fronts,” says Goldcorp's technical head Ivan Mullany. Rather than wait for breakthroughs by other companies, Goldcorp is investing in new technology to “bring it into the field and work out the kinks as we go.”
As world leaders signed the Paris climate agreement in 2015, a geologist working for diamond giant De Beers pitched her phd thesis to a group of colleagues.
All rocks slowly absorb carbon, Dr. Evelyn Mervine explained, but so-called “ultramafic” rocks absorb CO2 relatively quickly. To a layman, they have a green tint and coral-like edges, but they are also rare at the earth's surface, having come from the earth's liquid mantle, exploding upwards through fissures and cooling quickly, forming carrot-shaped columns.
Sometimes those columns are rich in diamonds. As such, ultramafic rocks are ground-up in huge quantities at diamond mines, and companies could use them to create a huge carbon reservoir.
Three years on and Dr. Mervine, 34, is now leading an initiative by De Beers to create the world's first carbon-neutral mine. Working with universities around the world that have been studying rock carbonation for 15 years, De Beers is looking at several ways to speed-up the natural process, from ventilating its waste (exposing it to air for longer), through to bioengineering (adding ponds of bacteria to its diamond mines).
De Beers has not disclosed its budget, but plans to publish its research, making it available to other companies. Nickel and platinum miners also handle ultramafic rock, and if all the industry's waste was fully carbonated, it could hypothetically suck-up 175 million tonnes of CO2 each year, equal to the emissions of London, New York and Hong Kong combined.
Those figures are not realistic “anytime in the near future”, Dr. Mervine says. But by combining the technology with renewables and better energy efficiency, De Beers believes it can turn at least one of its mines carbon-neutral in the next five to ten years. “We want to keep it simple and then there's always room to grow.” Dr. Mervine says. “Imagine if all companies committed to being carbon-neutral.”
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CORRECTION: Penasquito's total gold resource corrected to 11.3 million ounces ($15bn)