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ELI5 Yahaaa

Nothing alive has the tool for it

Why Does Plastic Never Rot?

Plastic does not rot because no bacterium or fungus evolved an enzyme that can cut its bonds.

An apple core Microbes have enzymesfor thisA plastic bottle Nothing alive can cutthese bonds
Rotting is not decay by time. It is something eating it.

  1. Step 1 of 5

    Rotting is eating.

    A fallen leaf Fungi andbacteriaarrive Enzymes cut the molecules up It becomessoilRot

    A fallen leaf does not vanish on its own. Bacteria and fungi take it apart for food, using enzymes shaped to fit its particular molecules.

  2. Step 2 of 5

    An enzyme is a key cut for one lock.

    A bacterium Enzymes shaped for thebonds it eats

    Every enzyme fits one shape of bond. Life has had a long time to evolve keys for wood, leaf, bone and fat — every molecule it has ever met.

  3. Step 3 of 5

    Plastic bonds are a lock nothing has a key for.

    A plastic chainNo enzyme fits itSo nothing can start eating

    The carbon-to-carbon backbone of most plastics has only existed for about a century. Nothing has had time to evolve an enzyme that fits it.

  4. Step 4 of 5

    Sunlight breaks it up but does not remove it.

    1 A bottle leftoutside2 Ultravioletsnaps thechains3 Microplastic —smaller, notgone

    Ultraviolet light does snap the chains, so plastic left outdoors goes brittle and crumbles. But the pieces are still plastic — just smaller ones.

  5. Step 5 of 5

    A few organisms have started to catch up.

    An apple corea few weeksA cotton shirta few monthsA plastic bottlecenturies — andstill only intofragments

    A bacterium that can slowly eat PET was found near a Japanese recycling plant in 2016. It is a beginning, but it is nothing like the speed of rot.

    That PET-eating bacterium was named Ideonella sakaiensis. In the wild it takes about six weeks to work through a film of plastic thinner than a hair.

The short version

Plastic lasts because nothing alive evolved an enzyme that fits its bonds, so sunlight only ever breaks it into smaller plastic.

Try it yourself

Bury a square of cotton and a square of plastic bag in a pot of damp soil. Dig them up in two months — one is going, one is untouched.

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