Making metals produces greenhouse gases, but where those gases come from, and how many, depends on the mine.

On land, most new nickel and cobalt now comes from tropical laterite pits. Bulldozers strip away rainforest, trucks haul ore up winding roads, and high-pressure acid plants eat huge amounts of coal-fired electricity to reach 260°C inside giant autoclaves.

Life-cycle studies show that turning one ton of nickel metal from these laterites releases about 2.8 tons of CO₂, plus residue ponds that must be managed for decades.

Deep-sea nodules skip many of those energy-hungry steps. The rocks lie loose on the seabed, so harvesters vacuum them up — no blasting, no overburden, no haul trucks.

A pump pushes the nodules to a ship, where they are rinsed and shipped straight to a refinery. Because nodules already contain manganese, copper and cobalt together, the refinery can co-produce those metals and spread its energy bill across four revenue streams.

Current engineering models put the cradle-to-gate footprint at around 1.6 tons of CO₂ per ton of nickel — roughly 40 % lower than high-pressure acid-leach routes on land.

That said, deep-sea systems still burn diesel for ship engines and riser pumps, and scientists are examining whether stirring up seabed sediments could release extra carbon trapped in the mud.

Companies are testing methanol or hybrid battery power to cut fuel use, while regulators plan to include CO₂ reporting in future mining licences.

So although ocean mining is not carbon-free, its streamlined logistics and multi-metal yield mean it starts with a smaller climate bill than many land pits — a key reason carmakers and clean-energy planners are watching the seafloor so closely.