Why is plastic non-biodegradable?

Plastic is non-biodegradable because its chemical structure is highly stable and resistant to breakdown by microorganisms. Most plastics are made of long chains of synthetic polymers derived from petroleum, which do not occur naturally in the environment.

Microorganisms such as bacteria and fungi do not have the necessary enzymes to break these complex polymer chains into simpler substances. As a result, plastic does not decompose through biological processes.

Instead of degrading, plastic may slowly break into smaller fragments due to physical factors like sunlight and heat, forming microplastics. However, these smaller pieces still remain in the environment and can cause harm to living organisms.

This resistance to natural decomposition is the main reason plastic persists in the environment for long periods and contributes to pollution.