Lowrey worries that the plume of seafloor sediment stirred up by the mining robots could travel with sea currents, disturbing ocean ecosystems. Sediment clouds could prove harmful to filter-feeders, environmentalists argue, undercutting the lower rungs of the food chain and potentially causing knock-on effects for other creatures.
"There's a serious concern that the toxicity from disturbing the deep sea can move up the food chain to the local communities," who live along the coast of Papua New Guinea, she said.
Johnston of Nautilus said his company is taking the sediment plume issue seriously, and that the company's machines are designed to minimize the undersea cloud through the collection procedure itself.
"When we're cutting, we have suction turned on," he said. "It's not like we're blowing stuff all over the place. We're actually sucking it up. So the plume gets minimized through the mining process."
Johnston added, "We go to great efforts to minimize the impact of the plumes. We're quite confident that the impact from these activities will be significantly less than some of these people claim."
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At Solwara-1, Nautilus is going after a type of deposit known as Seafloor Massive Sulfides (SMS), which form next to subsea hydrothermal vents at the margins of tectonic plates.
The deposits, which include copper, gold, and potentially other valuable minerals, collect after cold water seeps into the earth and becomes geothermally heated, dissolving metals and sulfides from the surrounding rocks before being spewed back out of the vent at temperatures up to 400 degrees Celsius and collecting on the sea floor — along with the minerals brought up from below.
The mining robots have been designed to operate in near-freezing temperatures, under pressure 150 times greater than at sea level.
The first robot, the auxiliary cutter, carves a level path to make way for the second machine, the bulk cutter, which is equipped with a wide, powerful cutting drum.
The third robot, called the collecting machine, follows behind them, slurping up the seawater slurry with a consistency like wet cement through internal pumps before sending the material to the ship at the surface via a riser system.
On the ship, the water is filtered, and solids larger than eight microns are removed, before being returned back into the ocean. The cargo is then transferred to a transport vessel and sent directly to customers in China.
Now, as Nautilus prepares for its maiden voyage, many will be watching from the sidelines — and if it succeeds, imitators will likely try to follow.
"If Nautilus goes ahead, it's going to open the gateway for this industry," Lowrey said.
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