Low-waste, single-step, sustainable extraction of critical metals from deep-sea polymetallic nodules.

To support the green energy transition, sustainable supplies of critical metals-60 million (metric) tons of copper, 10 million tons of nickel, and 1 million tons of cobalt-annually by 2050 are essential. These metals are currently sourced from declining terrestrial reserves, making deep-sea polymetallic nodules a promising alternative. However, current metal extraction methods are lengthy and energy and carbon intensive, emitting 45, 28, and 4 tons of carbon dioxide equivalent per ton of nickel, cobalt, and copper, respectively. We present a fossil-free hydrogen plasma-based reduction process, powered by green hydrogen and renewable energy, which condenses calcination, smelting, reduction, and refining into a single-step metal extraction, reducing direct carbon dioxide emissions by up to 90% and improving energy efficiency by up to 18%. In addition, we demonstrate selective copper recovery via a heat treatment requiring no acids or reducing agents, offering a more sustainable and cost-effective pathway for critical metal extraction from polymetallic nodules.