Companies leading the effort to collect battery metals from the bottom of the ocean say seabed mining is inevitable despite high-profile environmental concerns.

The battle is over the trillions of nodules littering the sea floor outside of the jurisdiction of any single nation. They contain manganese, nickel, cobalt and copper, all of which are either used in electric vehicle batteries, grid scale energy storage or other green technology like wind turbines and solar arrays.

Covering more than half of the total area of the world's oceans, the international area in question is governed by the 1982 United Nations Convention...