A single-use plastic (PET) bottle takes roughly 450 years to decompose when left in nature. But that number hides the real problem: a plastic bottle never truly returns to the earth. Instead of biodegrading, it slowly fragments into microplastics that stay in the water, soil, and food chain effectively forever.
Why does it take this long?
Plastic bottles are made from polyethylene terephthalate (PET) — a synthetic polymer engineered to be durable. Those same properties make it almost impossible for microorganisms to break down, so instead of biodegrading it photodegrades: sunlight makes it brittle and it cracks into ever-smaller pieces. The plastic doesn't disappear — it just becomes invisible.
Where it sits on the timeline
Frequently asked questions
Decomposition times are approximate and vary substantially with material composition and environmental conditions. See the methodology and primary references used for this guide.