Yes, cardboard can be composted, but it needs to be prepared correctly

Plain cardboard breaks down in a compost pile or bin, but only if you remove the tape, labels, and plastic windows first. Corrugated cardboard (the wavy kind in shipping boxes) decomposes faster than solid cardboard, and both work better when shredded or torn into smaller pieces. The key is that cardboard is mostly cellulose—the same material in leaves and straw—so microorganisms in your pile will eat it, but they need time and the right conditions.

Cardboard alone will not heat up your pile or speed decomposition. It works best mixed with nitrogen-rich materials like food scraps, grass clippings, or manure. If you layer it with those materials and keep the pile moist and turned, cardboard will break down in a few months to a year, depending on how finely you shred it and how active your pile is.

Key Takeaways

  • Remove all tape, labels, plastic windows, and ink-heavy printing before adding cardboard to your compost.
  • Shred or tear cardboard into strips or small pieces so it breaks down faster than whole sheets.
  • Mix cardboard with nitrogen sources like food scraps or grass clippings, since cardboard alone is too carbon-heavy.
  • Cardboard takes three to twelve months to fully decompose depending on pile temperature, moisture, and how small the pieces are.
  • Waxed, glossy, or colored cardboard should not go in your compost because the coatings may contain chemicals that slow decomposition.

What cardboard is safe to compost

Plain, unprinted corrugated cardboard from shipping boxes is the safest choice. This is the brown, wavy-layered material used for most product boxes. Cardboard from cereal boxes, paper towel tubes, and egg cartons also works, as long as the printing is minimal and uses soy-based or water-based inks. If you can rub the ink off with your finger, it is likely safe.

Newspaper and kraft paper (the tan paper used in grocery bags) compost even faster than cardboard because they are thinner. You can treat them the same way—tear them up, mix with nitrogen sources, and add to your pile. The key difference is that cardboard has more structure, so it takes longer to break apart.

What to remove before composting

Packing tape, labels, and plastic windows must come off before the cardboard goes into your pile. Packing tape is plastic and will not decompose. Glossy labels often have a plastic coating. Plastic windows in boxes (like on cereal or bakery boxes) are polyethylene and belong in the recycling bin, not compost.

Avoid cardboard that is waxed, laminated, or coated with a shiny finish. This includes frozen food boxes, takeout containers, and some beverage packaging. The coating prevents water from reaching the cardboard fibers, so decomposition stalls. If you are unsure whether a box is waxed, try tearing it—waxed cardboard will not tear cleanly and will feel slick on the inside.

Heavily printed cardboard—like boxes with full-color graphics covering most of the surface—should be avoided. The inks used in commercial printing may contain heavy metals or other chemicals. Minimal printing (a logo or text on one side) is generally fine, but when in doubt, recycle the box instead.

How to prepare cardboard for faster breakdown

Shredding or tearing cardboard into strips or small squares speeds decomposition significantly. A whole sheet of cardboard can take a year or more to break down. Torn into 2-inch pieces, it may decompose in three to six months. You do not need a machine—tear it by hand or cut it with a utility knife or scissors.

Wet the cardboard before adding it to your pile. Dry cardboard repels water and slows the work of decomposing microorganisms. Soak it in a bucket or spray it with a hose, then layer it into your pile. Wet cardboard also compacts more easily, which helps it mix with other materials.

Layering cardboard with other compost materials

Cardboard is a carbon source, which means it is high in carbon and low in nitrogen. Your compost pile needs a balance of carbon and nitrogen to heat up and decompose efficiently. A good rule is to layer cardboard with materials that are nitrogen-rich: food scraps, grass clippings, coffee grounds, manure, or plant trimmings.

A straightforward pattern is one layer of torn cardboard, then one layer of food scraps or grass clippings, then another layer of cardboard. This creates a sandwich that allows air and moisture to move through while keeping nitrogen and carbon mixed. If your pile is mostly cardboard with little else, decomposition will be slow and the pile may smell sour or attract pests.

Keep the pile moist—like a wrung-out sponge—and turn it every week or two if you want faster breakdown. Turning mixes materials, introduces oxygen, and speeds the work of microorganisms. A pile that sits undisturbed will still compost cardboard, but it may take twice as long.

How long cardboard takes to compost

In an active, hot compost pile (one that is turned regularly and stays between 130 and 150 degrees Fahrenheit), shredded cardboard can break down in three to six months. In a slower, cooler pile, expect six to twelve months. Whole sheets of cardboard may take a year or longer, even in ideal conditions.

Temperature matters most. A pile that heats up quickly (because it has plenty of nitrogen-rich materials) will decompose cardboard faster than a cool pile. If you live in a cold climate, cardboard will decompose more slowly in winter and faster in warm months. Moisture also affects speed—a dry pile slows decomposition, while a wet pile that is too soggy may become anaerobic (oxygen-starved) and smell bad.

Cardboard in commercial composting facilities

If your area has a municipal composting program, cardboard is almost always accepted. Commercial facilities reach higher temperatures and have equipment that shreds materials, so cardboard breaks down much faster than in a home pile—often in four to eight weeks. Check your local program's website or call to confirm that plain cardboard is accepted and whether you need to remove tape and labels (most do require this).

Some programs accept waxed cardboard or printed cardboard that home composters should avoid, because the facility's heat and processing can handle those materials. Always check your program's rules before dropping off cardboard, since requirements vary by location.

Frequently Asked Questions

Can I compost cardboard with ink on it?

Minimal ink from soy-based or water-based inks is generally safe. If the printing covers most of the box or uses glossy, heavy inks, recycle it instead. When in doubt, tear off the printed section and compost only the plain cardboard.

What about pizza boxes?

Pizza boxes are often coated with a thin layer of wax or plastic to prevent grease from soaking through. If the inside is slick or shiny, do not compost it. If it is plain cardboard with grease stains, you can compost it, but remove any plastic or foil inserts first.

Can I put whole cardboard boxes in my compost pile?

Yes, but they will decompose very slowly—often a year or more. Tearing or shredding them into smaller pieces speeds the process to three to six months. Whole boxes also take up more space and can create air pockets that slow decomposition.

Does cardboard attract rats or other pests?

Cardboard itself does not attract pests, but food scraps mixed with it do. Keep your pile covered or buried, and avoid leaving food scraps on the surface. If you have a pest problem, it is usually from the food, not the cardboard.

Can I compost laminated or glossy cardboard?

No. Laminated or glossy coatings prevent water from reaching the cardboard fibers, so decomposition stalls. These boxes should go in the recycling bin instead.