Cardboard is one of the most useful "brown" (carbon) materials you can add to a compost pile — it's abundant, free, and balances out wet, nitrogen-heavy kitchen scraps. But not every box qualifies, and the type of cardboard matters more than most people realize. Here's how to tell plain cardboard from the kind that shouldn't go in your pile.
Quick Answer
Yes, plain uncoated cardboard composts well — think shipping boxes, cereal boxes (with the liner removed), egg cartons, toilet paper and paper towel rolls. No, not glossy, waxed, or heavily printed cardboard — the coatings and inks don't break down the way plain paper fiber does.
Cardboard That Composts Well
- Plain corrugated shipping boxes (the brown, unbleached kind)
- Cereal and cracker boxes — once you remove the plastic or foil liner inside
- Egg cartons (paper pulp type, not styrofoam)
- Toilet paper and paper towel rolls
- Paper-based packaging inserts (not the plastic bubble kind)
These all break down as "browns" — the carbon-rich material that balances "greens" (food scraps, grass clippings) in a healthy compost pile. A pile that's too heavy on greens gets slimy and smells; browns like cardboard fix that balance and help keep airflow moving through the pile.
Cardboard to Keep Out
- Glossy or heavily printed cardboard — magazine-style printing and coatings often use inks and finishes that don't break down cleanly
- Wax-coated cardboard (some produce boxes and freezer packaging) — the wax coating resists decomposition and can leave waxy residue in finished compost
- Cardboard laminated with plastic (many frozen food boxes, some shipping mailers) — the plastic layer won't break down at all
- Heavily taped or stickered boxes — remove all tape, labels, and shipping stickers first; plastic tape doesn't decompose and will still be there at harvest
How to Prep Cardboard for Composting
- Remove all tape, labels, and stickers. Even small amounts of plastic tape will still be there months later.
- Tear or shred it. Whole flattened sheets of cardboard mat down, block airflow, and take significantly longer to break down. Tearing into smaller pieces — a few inches across — speeds decomposition considerably.
- Wet it before adding, if it's very dry. Dry cardboard can actually pull moisture out of the rest of your pile initially; dampening it first avoids that.
- Layer it with greens. Alternate cardboard with food scraps or grass clippings rather than adding one large batch of straight cardboard.
Frequently Asked Questions
Can I compost pizza boxes? The plain cardboard parts, yes — but greasy sections heavily saturated with oil should be torn off and composted separately (oil in large amounts can slow decomposition) or trashed if very saturated.
Do I need to remove the tape and labels first? Yes, always. Plastic tape and most shipping labels don't break down and will still be visibly intact in finished compost.
Is shredded cardboard better than whole boxes? Significantly. Shredded or torn cardboard breaks down much faster and doesn't mat down the way whole flattened sheets do, which can otherwise block airflow through the pile.
Can colored or printed cardboard go in compost? Simple black-and-white printing on plain cardboard is generally fine in moderate amounts. Heavy, glossy, full-color printing — the kind used on retail packaging — is better left out, since some inks and coatings don't break down cleanly.
Do electric composters need cardboard added for balance? Not in the same way an outdoor pile does. Electric composters like Reencle run a contained, temperature-managed microbial process rather than an open carbon-to-nitrogen balance system, so they're built around food scraps rather than needing bulk paper or cardboard added for balance.
The Bottom Line
Plain, uncoated cardboard is genuinely useful compost material — it's free carbon that balances wet food scraps and helps keep a pile from turning slimy. The dividing line is coatings and printing: if it's glossy, waxed, or plastic-laminated, tear off what you can compost and trash the rest. Torn or shredded plain cardboard, layered with your regular scraps, is the version that actually works.
References
- U.S. Environmental Protection Agency. Composting at Home. https://www.epa.gov/recycle/composting-home
- Cornell Waste Management Institute. Compost Chemistry and the Biology of Decomposition. https://compost.css.cornell.edu/chemistry.html
