can you compost plastic?
No — plastic never becomes compost; it only fragments into microplastics that permanently contaminate your finished pile.
which bins can take it?
- hot pile no
- cold pile no
- worm bin no
- bokashi no
- tumbler no
- curbside no
- curbside: Plastic is the number-one contaminant municipal composters screen for — it downgrades entire loads.
why?
Compost microbes run on enzymes that evolved to cut plant polymers like cellulose and lignin, and those enzymes can't grip the carbon backbone of polyethylene or polypropylene. Instead of decomposing, plastic only breaks apart: UV light, heat, and every turn of the pile grind it into smaller and smaller fragments that are still plastic, and the finest of them slip through a compost screen straight into garden soil.
what to do instead
Recycle rigid #1 (PET) and #2 (HDPE) containers curbside — those resins have real end markets. Most other plastic belongs in the trash unless your local program accepts more numbers. Items with a BPI certification mark are a different material with different rules.
often confused with
- Compostable Bioplastics — Certified compostable PLA looks identical to regular plastic but is a different polymer — and even it needs an industrial facility, not a backyard pile.
quick answers
How long does plastic take to decompose?
Estimates run from 20 years for a thin bag to 450 or more for a bottle, but 'decompose' is generous — the polymer mostly just fractures into smaller and smaller particles that stay in the environment.
What if plastic accidentally got into my compost?
Pick out every visible piece before spreading, and screen the batch if you can. The fragments won't poison your plants, but they never leave the soil once they're tilled in, so it's worth the extra pass.
Is 'biodegradable plastic' the same as compostable?
No. 'Biodegradable' is an unregulated marketing word, often applied to oxo-degradable plastics that just crumble into microplastics faster. Compostable claims are only meaningful with BPI or TUV certification behind them.