can you compost styrofoam?
No — Styrofoam is polystyrene plastic that is roughly 95% air; it never rots, it only crumbles into beads that scatter through a pile.
which bins can take it?
- hot pile no
- cold pile no
- worm bin no
- bokashi no
- tumbler no
- curbside no
- curbside: Foam beads are among the hardest contaminants for facilities to screen out — keep every scrap away from the cart.
why?
Expanded polystyrene is petroleum plastic blown into a foam that's about 95–98% air, which is why a big cooler weighs ounces. No compost organism makes enzymes that cleave the styrene backbone, so the foam simply weathers into static-charged beads that cling to everything and are nearly impossible to sieve back out of compost.
what to do instead
Trash it, or look for a foam-densifier drop-off — some counties and shipping stores collect clean EPS blocks for recycling. Cornstarch packing peanuts, the kind that dissolve in water, are the compostable exception.
often confused with
- Starch Packing Peanuts — Starch peanuts dissolve in a glass of water within minutes; polystyrene peanuts float forever. Run that test before composting any peanut.
quick answers
Will Styrofoam ever break down in a landfill?
Buried EPS is effectively permanent — sunlight can chalk the surface, but underground there's no UV and no organism that eats it, so estimates of 500+ years are, if anything, optimistic.
Can I crumble Styrofoam into potting soil for drainage?
Skip that old hack. Modern horticulture guidance says foam beads migrate upward, blow away, and don't actually improve drainage the way coarse bark or perlite does — and they leave microplastic behind.