From Business Day-Australia
May 18, 2008
THE first deep-sea mining machines — for extracting gold, silver and copper deposited near volcanic fissures on the ocean floor — are being built by a British engineering company. The machines, which will resemble giant, abrasive vacuum cleaners, are at the forefront of an emerging underwater mineral extraction industry that is sounding alarm bells among marine biologists and environmental scientists.
A £33 million ($A68.5 million) contract for two sea-floor mining tools, capable of working at depths of more than 1700 metres, was awarded last December to a Newcastle-upon-Tyne firm, Soil Machine Dynamics. The machines could begin excavation work by 2010 in the Pacific, launching a new era in sub-sea exploration and mining.
Recovering these "poly-metallic" minerals, which are found in far higher concentrations than land-based ores, will generate huge earnings at a time when commodity prices are hitting record levels.
"We are leading the mining industry into the deep oceans," said Scott Trebilcock, vice-president of business development at Nautilus Minerals Inc, the Canadian company that has ordered the machines and whose operational management is based in Brisbane.
"This is as big a change as it was for the oil and gas industry when it went offshore in the 1960s and '70s," he said. "Billions of dollars have been spent over decades developing (underwater) pumps, hydraulics and trench-digging machinery. We can use their technology for new targets: the poly-metallic deposits that contain gold, silver, zinc and copper."
Nautilus' first project, the Solwara 1 field, is within Papua New Guinea's territorial waters, and the firm has also taken up licence options on sites near Tonga, Fiji and New Zealand. Those locations have been chosen because they are close to volcanic activity at the margins of the earth's tectonic plates.
"Deposits are formed from heated sea water," Mr Trebilcock said. "As it filters deeper into cracks, it absorbs sulphur and becomes acidic. It can reach 300 Celsius and dissolves minerals until it bubbles up and hits water on the ocean floor, which is at approximately 2 Celsius."
The metals are deposited on the seabed as massive sulphides that resemble giant "elephant turds", according to one oceanographer.
Nautilus will work on old underwater vents that have cooled, some way back from the super-heated, active plate edges. "Our material is 8%-10% copper," Mr Trebilcock said. "In land mines, the average is 0.59%. So for every tonne of copper produced, we move 40 times less material.
Similar SMS deposits lie on ocean floors around the world, particularly in the Arctic and along the Mid-Atlantic Ridge. Those areas, however, are at far greater depths.
Soil Machine Dynamics is designing and assembling a tool that has a rotating cutting head — like the machines used to hew coal out of underground seams — surrounded by a giant suction pipe. The company describes the equipment as "a novel design for recovering ore which is found in massive sulphide deposits in rugged terrain. It draws on technology developed in recent projects for trenching systems." The two sea-floor mining systems will suck up 1.5 million tonnes of ore annually.
Mr Trebilcock said the operation would cause far less environmental damage than a similar-sized onshore mine. "There's no disturbance to the site around the mine," he said. "We'll have no waste rock. Everything we take up will be smelted.
"We have carried out an environmental impact study, which will be published this year.
"Oil and gas (companies) disturb a far larger area when they open up a new field. The dredging industry takes millions of tonnes off the ocean floor. We have significant (environmental) advantages over land-based companies."
However, some environmental groups, including WWF, are concerned that underwater mining will harm vast tracts of the seabed. "These sites have limited physical integrity and great biodiversity," Simon Cripps, director of WWF's global marine program, told Chemistry World magazine. "We would like to see a thorough, independent impact assessment before any mining work begins."
Catherine Coumans, a co-ordinator at Mining Watch Canada, has been to Papua New Guinea to examine the impact of mining. "I have studied mines … where the tailings (wastes) are flushed out to sea or simply dumped in rivers," she said. "(Papua New Guinea) has, tragically, some of the worst forms of mining and disposal. Now it is going to have experimental undersea mining.
"I would challenge the company to provide an independent scientific study."