Why exactly isn't PLASTIC bio-degradable in nature?

Answer 1

Plastic is made by creating a polymer, a molecule that is a long chain of the same basic building block. With plastics, the building block is often a simple hydrocarbon, like ethylene, which is formed into chains of polyethylene (the stuff a typical plastic bag is made of).

The microorganisms that "bio-degrade" (decompose) organic compounds have the enzymes to break down simple molecules. Breaking down the complex polymer chains is more difficult. The enzymes usually attack a particular bond in the simple molecules, but in a polymeric plastic that degrades slowly, that particular bond is modified or tied up in the polymer's chain, and therefore non-reactive to the enzyme.

Answer 2

Although plastics have had a remarkable impact globally, it has become increasingly obvious that there is a price to be paid for their use.

Plastics are durable and degrade very slowly. In some cases, burning plastic can release toxic fumes. Also, the manufacturing of plastics often creates large quantities of chemical pollutants.

By the 1990s, plastic recycling programs were common in the United States and elsewhere. Thermoplastics can be remelted and reused, and thermoset plastics can be ground up and used as filler, though the purity of the material tends to degrade with each reuse cycle. There are methods by which plastics can be broken back down to a feedstock state.