Wearing a white lab coat and with a gas mask within reach, Ole Jorgen Gronvold measures the humidity of an intriguing dark powder touted as the planet's next "black gold."

But this "black gold" — a term that usually refers to oil — is actually good for the Earth.

In southeastern Norway lies Europe's biggest plant for recycling used or defective electric car batteries, turning them into a powder, or "black mass," made up of nickel, manganese, cobalt, lithium and graphite.