Metal is congealed energy, and the energy is mostly coal

I spent two days planning how to melt scrap metal in my backyard, and somewhere in the middle I asked my assistant a simple question: is metal production basically an energy problem, and does the world still solve it by burning fossil fuels?

The verified answer rearranged how I think about every object on my desk.

Nature doesn’t store metal as metal. It stores it as ore: oxidized, rusted-out, the low-energy state the metal wants to be in. Refining is shoving that energy back in. A smelter is a machine for pushing matter up an energy hill, and the hill is enormous.

Aluminium is the clearest case. Getting it out of its oxide takes electrolysis at about 13 kWh per kilogram, and the smelting industry consumes roughly three to four percent of all electricity generated on Earth. And the global average mix behind that electricity is 57% coal. That average is really China, which makes most of the world’s aluminium on a coal grid; Europe’s smelters run ~93% hydro, and the Gulf’s run on gas. A can of soda is, in a fairly literal accounting, a small block of congealed coal.

Steel is stranger: there the coal isn’t just the power source. Coke, which is baked coking coal, is the chemical agent that rips oxygen off the iron ore inside a blast furnace. The carbon does the chemistry, not just the heating. About 70% of world steel is made this way, and coal supplies roughly three quarters of the entire steel sector’s energy. Crude oil, which I had vaguely assumed was in this story, barely appears in it at all. Oil moves things and becomes plastic. Coal makes metal.

Here is the number that reorganized my workshop plan: recycled aluminium takes about 95% less energy than primary. 8.3 gigajoules a tonne against 186. Melting scrap is the single biggest energy shortcut in metallurgy. The metal in a dead extrusion offcut already climbed the hill. You just warm it back up.

So the backyard plan inverted. I was pricing furnaces to make metal. The correct frame: buy or scavenge metal that someone else already paid the coal for, and spend the effort on the part that actually carries value: the shape. A 3-metre plastic pipe costs twenty dirhams and contains about one dirham of plastic; the other nineteen are for the extrusion. Material is cheap everywhere. Form is where the money lives.

Two footnotes worth keeping. The place I live is quietly the exception to the coal story: the UAE smelts on gas and has shipped the world’s first solar-powered aluminium, and recently the first made with nuclear power. And steel’s future swap is hydrogen replacing coke: iron ore plus H₂ gives you iron plus water vapor. The exhaust of the coming steel industry is steam.

Until then: the world makes metal by burning coal to climb an energy hill. In my backyard, the plan is to stop climbing: melt the junk, and make the forms.