If you ship products in boxes, you’ve probably faced the loose-fill decision: reach for the classic pink or white styrofoam peanuts, or switch to the plant-based cornstarch kind that dissolve in a sink. The two look almost identical in a box, but they behave very differently once they’re wet, stored for months, or thrown away.
This guide compares cornstarch (starch-based) packing peanuts and expanded polystyrene (EPS) styrofoam peanuts on the things that actually matter for a shipper: cushioning performance, durability, cost, and what happens to them after the package is unpacked.
Quick Answer
For cushioning fragile items during a single shipment, cornstarch and styrofoam packing peanuts perform about the same — both interlock, absorb shock, and fill voids well. The real differences show up outside the box: styrofoam is more durable and can be reused many times but is hard to recycle and never biodegrades, while cornstarch peanuts dissolve in water and are typically certified compostable only for industrial composting facilities (not automatically for a backyard bin), and they soften in humid storage and cost a bit more per bag.
How They Compare on Protection and Handling
Both materials are shaped to lock together under pressure and flow freely when loose, which is what lets a handful of peanuts cradle an item and absorb impacts during transit. In side-by-side use, biodegradable cornstarch peanuts offer cushioning and void-fill performance that’s comparable to EPS foam peanuts for typical retail shipping — neither has a clear edge in shock absorption for a one-way shipment.
Where they diverge is durability over time and repeated use. EPS peanuts are essentially inert plastic foam: they hold their shape almost indefinitely, so a shipping-and-mailing store can collect used ones and reuse them in outgoing packages for years. Cornstarch peanuts are hydrophilic — they pull moisture from the air, which over weeks or months in a humid garage or basement can make them soften, get sticky, or start to break down even before they’re used. If you store loose-fill for long periods before shipping, that’s worth factoring in.
Static is another practical difference. Plain (non-pink) EPS peanuts can build up static charge and cling to skin, clothing, and packing tape, and pink antistatic peanuts need a chemical treatment to prevent that around electronics. Cornstarch peanuts are naturally non-static, so they don’t need any additive to be safe for shipping circuit boards, laptops, or other sensitive electronics.
Cost, Disposal, and Environmental Impact
Cornstarch peanuts typically cost somewhat more per bag or cubic foot than EPS peanuts, since starch-based feedstock and manufacturing run higher than commodity polystyrene foam. For high-volume shippers, that difference adds up, though many businesses treat it as the price of avoiding plastic-waste complaints from customers.
End-of-life is the biggest practical gap between the two, but it’s worth reading the label carefully rather than assuming any “compostable” peanut can go straight into a backyard bin. Cornstarch peanuts dissolve in plain water within seconds to minutes, which makes drain disposal easy anywhere. Many are also certified compostable to the ASTM D6400 standard, often through third-party verification from the Biodegradable Products Institute (BPI) — but that standard and certification are built around commercial and municipal composting facilities, which run hotter and more consistently than a home pile. BPI certification does not, on its own, confirm a product will break down in backyard composting. If you specifically want peanuts you can toss in home compost, look for a dedicated home-composting mark such as TÜV Austria’s “OK compost HOME” certification, or check whether your municipality accepts industrial-compostable packaging before assuming a home pile will fully break it down.
EPS peanuts, by contrast, are technically recyclable but rarely accepted in curbside bins because most municipal recycling facilities aren’t set up to handle lightweight foam. The EPS industry maintains a network of drop-off and mail-back locations (searchable through the EPS Industry Alliance’s recycling locator), and many UPS Store, FedEx, and independent pack-and-ship locations will take clean peanuts to reuse — but that requires the shipper or recipient to actively seek out a drop-off point rather than just tossing them in the bin. Left in the environment, polystyrene foam persists for a very long time and readily breaks into small pieces that spread easily, which is why it’s a common target of local foam-foodware and packaging bans.
Tips and Common Mistakes
Don’t store cornstarch peanuts in a damp basement, garage, or near a water heater — humidity is their weak point, and a bag that’s gone soft or clumped won’t cushion well or flow properly into voids. Keep them in a sealed bag or bin in a dry area.
Don’t assume EPS peanuts are curbside-recyclable just because the plastic resin (#6 polystyrene) has a recycling symbol on it — check for a local drop-off or mail-back option instead, or ask a nearby shipping store if they’ll take clean peanuts for reuse.
Don’t assume a “compostable” cornstarch peanut will break down in your backyard compost pile. ASTM D6400 is a commercial/industrial composting standard, and BPI certification verifies compliance with that standard for industrial facilities — neither one, by itself, confirms suitability for home composting. For backyard composting, look specifically for a separate home-compost certification like OK compost HOME, or just dissolve the peanuts in water instead.
Don’t mix pink antistatic EPS peanuts into a batch you’re sending for foam recycling without checking first — the antistatic coating on pink peanuts can make them harder for some recyclers to process alongside plain white ones.
Do pair either type with proper box sizing. Packing peanuts fill voids and add cushioning, but they can’t compensate for a box that’s too big for its contents — items can still shift and collide inside a loosely packed box regardless of which peanut you use.
Explore more: more sustainable packaging comparisons.
Cornstarch packing peanuts vs styrofoam FAQs
Are cornstarch packing peanuts as strong as styrofoam for shipping fragile items?
Yes, for typical shipping use both provide comparable shock absorption and void-fill protection. The difference isn’t strength during a single shipment — it’s how each material holds up in storage and after use.
Can I put cornstarch packing peanuts in my backyard compost bin?
Not necessarily, even if the bag says “compostable.” ASTM D6400 is a standard for commercial and municipal composting, and certification through the Biodegradable Products Institute (BPI) verifies compliance with that industrial-facility standard — by itself, it doesn’t confirm the peanuts will break down in a backyard pile, which runs cooler and less consistently. For peanuts meant to break down in backyard compost, look for a separate home-composting certification such as TÜV Austria’s “OK compost HOME” mark — otherwise, dissolving them in water and pouring them down the drain is the more reliable disposal method.
Why do styrofoam packing peanuts stick to everything with static?
Uncoated EPS foam readily builds up static charge, causing peanuts to cling to skin, clothing, and tape. Pink packing peanuts have an antistatic treatment specifically to prevent that near electronics; cornstarch peanuts are naturally non-static without needing any coating.
Can I reuse styrofoam packing peanuts for future shipments?
Yes — that’s one of EPS foam’s main advantages. Because it’s durable and doesn’t degrade, clean styrofoam peanuts can be reused many times, and many shipping stores accept donated peanuts for exactly this purpose. Cornstarch peanuts aren’t meant for long-term reuse since they absorb moisture over time.
Find the Right Packaging Supplier
Search the free Packaura supplier directory — filter by material, certification, and location to find vetted suppliers. Search the Supplier Directory.
Want packaging news in your inbox? Subscribe to the free newsletter.
Photo: Alex Flury at English Wikipedia / Public domain, via Wikimedia Commons.