Aluminium can
Where does an aluminium drink can come from, and where does it go?
Aluminium is the most abundant metal in Earth's crust, but in nature it is always tightly bound to oxygen, and separating it takes a lot of electricity. That's why recycling a can uses only about 5% of the energy needed to make new aluminium.
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In numbers
- ≈ 8%of Earth's crust is aluminium (by mass)
- ≈ 5%of the energy is needed to recycle (vs. making new)
- ≈ 75%of all aluminium ever made is still in use
In five stops
Where were its atoms born?
Aluminium is born inside massive stars, when magnesium made after carbon fusion captures protons and neutrons. When these stars exploded as supernovae, the aluminium was scattered into space and eventually ended up in Earth's rocks.
How did nature prepare it?
Aluminium is strongly drawn to oxygen; it is never found pure in nature, only in minerals in rocks. About 8% of Earth's crust by mass is aluminium. In hot, rainy regions, rocks are washed by rain over long periods and break down; other substances are carried away and aluminium-rich bauxite is left behind.
What did people do?
Separating aluminium from its oxygen was so hard that before the 1850s it cost more than gold. In 1886 Charles Martin Hall and Paul Héroult independently found the same method: splitting aluminium oxide with electricity in molten salts. In 1888 Carl Josef Bayer developed a way to get pure aluminium oxide from bauxite; both methods are still used today. The aluminium drink can came onto the market in 1959.
What happens when we use it?
The can is light and doesn't rust: a thin protective oxide layer forms on aluminium's surface as soon as it meets air. The inside is coated with a thin lining so the drink doesn't touch the metal.
Where does it go next?
Aluminium can be recycled almost endlessly. Collected cans are melted into new cans or other products, using only about 5% of the energy needed to make new aluminium. That's why about 75% of all the aluminium ever made is still in use. A can thrown in the rubbish wastes all the electricity that went into making it.
Did you know?
Before the 1850s aluminium cost more than gold. Today it is cheap enough to make throwaway cans; the difference is the electrical method that separates it from its oxygen.
Related:Where did iron come from? →Where does the electricity in the socket come from, and where does it go when we use it? →
Sources for this page
- Aluminium (opens in a new tab)
- Bauxite (opens in a new tab)
- Hall–Héroult process (opens in a new tab)
- Bayer process (opens in a new tab)
- Aluminium recycling (opens in a new tab)
- Drink can (opens in a new tab)