A reasoned judgement will hinge on many things, including how much you are concerned by the toll from conventional mining. More than half of the world’s cobalt currently comes from the Democratic Republic of the Congo, which has had a dismal record for protecting the environment and the well-being of the people who live and work around its mines.
Would having another large source available—the deep Pacific—help corporate buyers pressure Congolese mining companies to clean up their act? This and other important questions will remain open for some time, but one critical component in the calculus—the degree of environmental disruption involved in collecting metal-rich nodules from the deep Pacific—should become much clearer after the Metals Company begins pilot operations later this year.
Those operations will be conducted from what formerly served as a petroleum drill ship, rechristened Hidden Gem. The giant vessel is now being outfitted to collect polymetallic nodules, which are gravel- to briquette-size concretions that can be found strewn almost like paving stones on certain parts of the deep-ocean floor. Unlike some other strategies for obtaining metal ores from the seafloor, getting them from nodules is more a matter of collecting than “mining” in the usual sense of the word.
Sometime in 2022, workers on the Hidden Gem will lower into the water a steel pipe of colossal proportions, one segment at a time, with a total length of 4 kilometers. But it won’t simply dangle over the seafloor, hoovering up nodules like a giant underwater vacuum cleaner.
“At the business end is the robotic collector vehicle,” explains Jon Machin, head of offshore engineering at the Metals Company. This vehicle is some 12 meters long and weighs 80 tonnes in air. In water, though, it weighs significantly less—just enough for the vehicle to gain traction as it propels itself, but not so much as to cause it to get mired in the mud.
Compressed air injected into the bottom of the pipe will create countless bubbles, which will help raise the mix of nodules, mud, and seawater.
A flexible conduit will connect the end of the steel pipe with the vehicle. As the vehicle moves over the bottom, it will funnel nodules through this flexible conduit and into the pipe, where they will be sent upward using what Machin calls “an air-lift system”: Compressed air injected into the bottom of the pipe will create countless bubbles, which will help raise the nodules, along with some mud and seawater.
Nodules will be separated from this slurry aboard the Hidden Gem, which will store them in its hold and discard what remains. The best depth to discharge the leftovers is not yet entirely clear. Doing so in shallow water could affect the abundant sea life that lives there, while releasing it too close to the seafloor wouldn’t give the mud an opportunity to spread and thin before …….
Source: https://spectrum.ieee.org/solar-power-from-space-caltechs-100-million-gambit