The scene around the flooded Whitehill Yeo pit in Devon, UK, resembles a lunar landscape. Until it was abandoned just a few years ago, an endless stream of diesel trucks carried china clay out of the mine seven days a week.
But don’t be fooled by the silence: this is very much an active site. It’s just that all the excavation is happening deep beneath the placid waters. This is a test bed, the first, for a new type of mining by underwater robots.
They are part of a European Union-funded project called ¡VAMOS! for Viable Alternative Mine Operating System. The goal is to extract mineral resources from abandoned, flooded mine sites previously considered too dangerous or costly to access. If the demonstration here at Whitehill Yeo works, these robots will go global, producing raw materials without digging new mines, and minus the environmental or noise problems that plague traditional mining.
Any time a mine is dug below the water table, it floods unless water is constantly pumped out. But mines have to be deep: many metallic ores are the result of volcanic action, and the deeper you go, the higher the ore quality.
Eventually, even mines with resources still untapped are abandoned because it becomes too costly to keep pumping out water, too unstable to keep miners safe, and too hot to keep them comfortable at geothermal depths.
But what if you could let a mine flood and keep working it anyway? Then, instead of fighting you, the water would turn into an ally: the liquid helps lift and transport rocks, cools motors and lubricates cutting equipment.
That means drilling and blasting, would become unnecessary. So would cooling at geothermal depths. And because separation of ore and rock is done on site, fewer trucks are needed to transport it for processing. The robot runs on swamp tracks on the floor of the lake, connected by an umbilicus to a small barge on the water’s surface. It crushes the minerals it finds and sends them as a slurry back up to the barge; after the water is removed from the slurry, it is returned to the flooded pit.
This approach even removes the toxic wastewater associated with mining. “Limiting the movement of wastewater seems an appealing component of this new technique,” says Gillian Galford at the University of Vermont.
The road to Whitehill Yeo as been rocky; one of the biggest problems the team had to overcome was how the robot would navigate and locate itself in the turbid, nearly opaque mining water. A new location system developed by the team’s Portuguese collaborators can pinpoint the mining vehicle’s position.
The trial at Whitehill Yeo is due to be completed at the end of October when a detailed environmental impact assessment will be published. “So far, we haven’t observed any environmental effects beyond the immediate working area, and nearby water bodies do not seem to be affected,” says Ian Stewart an independent environmental consultant with Fugro GB Marine Limited.
“From an environmental perspective, it makes sense to reopen an existing mine rather than excavate a new pit,” says Stewart, but warns it may not be suitable for all mines. In its second trial, planned for June 2018, the mining robot will face the granite bedrock of the Smreka iron open-pit in Bosnia and Herzegovina.
Edine Bakker of ¡VAMOS! told New Scientist that she hopes the work will lead to a world where mining operations are more sustainable as robots will work unseen, unheard and with minimal environmental disturbance.
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