実際に動いているもの
Bauxite is red soil. It is refined into alumina, and alumina is smelted into aluminium by passing an enormous electric current through it. Because that last step is essentially electricity in solid form, the smelter is built next to cheap power rather than next to the mine — often on a different continent.
- 素材
- Bauxite
- 種類
- Gibbsitic bauxite, roughly 45% alumina, low silica
- 起点
- Guinea — The Boké plateau, part of the largest bauxite reserve base in the world
工程ごと、越境地点ごとに
Guinea · Boké, Guinea 保管者 Mining consortia with the Guinean state (採掘会社)
Scraping the plateau
Bauxite lies at or near the surface under a thin overburden. It is ripped and loaded — no blasting, no grinding, no flotation. The simplest large-scale mining there is.
なぜここか: Tropical weathering over millions of years made this. West Africa and northern Australia have most of it.
China · Kamsar, then Chinese and Gulf refineries 保管者 Traders and refiners (トレーダー)
Rail to the coast, then a Capesize
Railed to a purpose-built port and loaded onto bulk carriers. Guinea ships hundreds of millions of tonnes a year of what is, physically, dirt.
なぜここか: An export ban would force refining onshore — several countries have tried exactly that with different minerals.
China · Alumina refinery 保管者 Refiner (精製業者)
The Bayer process
Digested in hot caustic soda under pressure. The alumina dissolves; the iron and silica do not, and settle out as red mud. The dissolved alumina is then precipitated and calcined to a white powder.
残りはどうなったか: Red mud is the largest single waste stream in the metals industry by volume, and it is caustic. Storing it safely is the defining problem of this step.
なぜここか: Refineries sit near ports and near smelters. Some are in Guinea now, but most of the capacity is not.
United Arab Emirates · Smelter, wherever power is cheap 保管者 Smelter (精製業者)
Electricity, made solid
Alumina is dissolved in molten cryolite at about 960 °C and an enormous direct current is passed through it. Aluminium collects at the bottom; the carbon anodes are consumed and must be constantly replaced.
残りはどうなったか: Roughly 125 tonnes of carbon anode is burned away — and that carbon started life as petroleum coke, from an oil refinery.
なぜここか: Iceland, the Gulf, Quebec, Siberia, Yunnan. All the same answer: cheap, reliable, uninterruptible electricity.
Germany · Rolling and extrusion mills 保管者 Fabricators (製造業者)
Frames, cans, cables, car bodies
Cast into billet and slab, then extruded or rolled. Recycled aluminium needs about a twentieth of the energy of primary, which is why scrap is worth so much.
なぜここか: Four tonnes of Guinean soil for one tonne of metal — and once it exists, it can be melted and reused indefinitely.
これは計算例である。公表された標準的な歩留まりと回収率を用いて、明示された出発量を追うものであり、比率は検証可能だが、特定の荷物の記録ではない。経路に関する事実——どの国を経由するか、どのような工程を経るか、なぜその素材を他の場所では処理できないか——は公開情報から編集している。