They might look like pebbles strewn across the seafloor, but to the unique animals of the ocean deep, polymetallic nodules are a crucial habitat.
To the mining firms vying to extract them, on the other hand, they promise to be a “battery in a rock”.
This month at a week-long meeting of the International Seabed Authority (ISA), those opposed to mining the nodules suffered a serious setback when they failed to take a first step toward an international moratorium on the controversial practice.
And on Tuesday a Nauru-backed company told AFP it would forge ahead with contentious plans to start industrial deep-sea mining in the Pacific in 2026, vowing to overcome environmental criticisms that have dogged the project.
The contract is for NORI (Nauru Ocean Resources Inc), a subsidiary of Canada’s The Metals Company.
Multiple companies have lined up exploratory contracts and pursued tests for these nodules. One of these is NORI, whose contract covers four zones totalling some 75,000 square kilometers (about 30,000 square miles) in the CCZ.
These nodules are mainly composed of manganese and iron, but they also contain strategic minerals such as cobalt, nickel and copper.
According to the ISA, the CCZ contains around 21 billion metric tons of nodules, which could correspond to a reserve of six billion metric tons of manganese, 270 million metric tons of nickel and 44 million metric tons of cobalt, exceeding the known totals of these three minerals on land.
Advocates of undersea mining point to their potential use for green technology, particularly for electric vehicles.
“A battery in a rock,” said The Metals Company.
“Polymetallic nodules are the cleanest path toward electric vehicles.”
But that is an argument rejected by environmental NGOs and some scientists.
This claim is “more public relations than scientific fact”, Michael Norton, of the European Academies’ Science Advisory Council, told AFP, calling it “rather misleading” to say that demand cannot be met without undersea minerals.
Unlike the other two types of subsea mining resources regulated by the ISA — including the mining of hydrothermal vents — nodules do not require digging or cutting.
In tests carried out at the end of 2022, NORI lowered a collector vehicle to a depth of 4.3 kilometers (about 2.7 miles).
It swallowed nodules and sediment and then separated them, transporting the nodules to the surface vessel via a giant pipe and discharging the sediment into the water.
Catherine Weller, global policy director at the conservation organization Fauna & Flora, said that while the nodules are lying on the seafloor, they cannot just be “plucked” individually.
The impacts on the wider ocean system of churning up sediment and releasing wastewater was “simply unknown”, she added.
Weller said the unique composition of the nodules which attracts mining firms is also what makes them such a special habitat for the creatures that live in the ocean depths.