What You Should and Shouldn't Add to Your Compost

Picture this you're standing over the bin with a banana peel in one hand and an old pizza box in the other, and you may be thinking is this actually going to break down, or am I about to ruin the whole pile? If you've paused before adding anything to your compost, you're not overthinking it.

The good news: compost really comes down to two things-what you're putting in, and roughly how much to add. Once you get a feel for that, you'll stop second-guessing if a banana peel is a safe option.

The Green and Brown Rule

Composting material can fall into two categories: greens (nitrogen-rich, usually moist — vegetable peels, grass clippings) and browns (carbon-rich, usually dry — fallen leaves, cardboard). Greens feed the microbes doing the work; browns give the pile structure and air so it doesn't turn into a soggy mound.

• Greens (nitrogen) — veggie scraps, coffee grounds, grass clippings. Feed the microbes doing the work. Aim for 1 part.
• Browns (carbon) — dry leaves,  plastic free cardboard, straw, twigs. Add structure and air. Aim for 2–3 parts.

What You Can Compost

Kitchen scraps: fruit and vegetable peels, cores, and rinds; coffee grounds and paper filters; tea bags without plastic mesh; crushed eggshells and their membrane; most nut shells except black walnut; stale bread, pasta, avocado pits (chop them or expect a slow break-down); corn husks and cobs, chopped.

Yard and garden waste: grass clippings and deadheaded flowers (green); fallen leaves, straw, and pencil-thin twigs (brown); spent tomato plants and bean vines, as long as they were healthy; cut flowers past their prime, provided they weren't treated with floral dye.

Paper and household items: shredded newspaper with black ink only; plain cardboard, torn small and soaked; unbleached paper towels; hair and pet fur; dryer lint, only from natural fibers; small amounts of untreated sawdust.

What You Should Never Compost

1. Meat, fish, bones, and dairy: attract pests fast and can carry pathogens through.
2. Fats, oils, and grease: coat other material and stall decomposition.
3. Pet waste from dogs and cats: can carry parasites that survive backyard compost temperatures.
4. Pressure-treated or painted wood: preservatives don't belong near food-growing soil.
5. Glossy or heavily colored paper: inks often carry heavy metals.
6. Diseased or pesticide-treated plants: spores and residue can persist through the pile.
7. Black walnut shells and leaves: contain juglone, which stunts tomatoes and peppers.
8. Plastic, metal, and glass: including bags labeled "biodegradable," which almost always need an industrial facility, not a simple bin in your yard.
9. Coal or charcoal briquette ash: unlike wood ash, it can contain chemicals harmful to plants, so keep it out of the pile entirely. 

Be Careful With These

• Citrus peels: fine in small amounts; the oils can repel earthworms in bulk. One orange peel a week is fine, a bag of rinds isn't.
• Onions and garlic: chop small and mix in thoroughly; large amounts can temporarily have a negative effect.
• Sawdust and pine needles: only from untreated wood, and sparingly; both are slow to break down.
• Seeded weeds: only safe in a pile that reliably holds 130–150°F. Otherwise, bag them separately.
• Grass clippings from a herbicide-treated lawn: the chemicals can persist and affect sensitive plants like tomatoes. Skip these unless you're sure the lawn hasn't been treated recently.

Composting Myths, Debunked

"You need a fancy tumbler or bin." A pile in the corner of the yard works fine, adding a tumbler just speeds this process up.

"Citrus and onions will ruin your whole pile." In normal kitchen-scrap quantities, they're a minor nuisance at worst, not a pile-killer.

"Rhubarb leaves are too toxic to compost." They're toxic to eat, but perfectly fine to compost — the compound doesn't survive decomposition.

Small-Space Alternatives

No yard, no problem.

Vermicomposting: a bin of red wiggler worms, handles kitchen scraps in something small enough for a balcony, and the castings make excellent fertilizer for container plants. 

Quick Troubleshooting 

Smells bad? Add dried browns and turn the pile for air. Not breaking down? Add greens, water it like a wrung-out sponge, and chop anything oversized. Attracting pests? Bury food scraps under 6" of brown material and skip anything animal-based.

FAQ

Are eggshells actually worth composting? Yes, crush them first so they break down instead of sitting there for years. They amend calcium in the soil.

How long until compost is ready to use? Usually after a few months. You'll know it's done when it's dark, crumbly, and smells like soil.

Does it matter what my raised bed is made of if I'm adding compost? Yes, honestly. Composted soil holds more moisture than average garden soil, and cheaper materials can warp or rot under that. Cedar handles it without issue.

Do I need to add worms myself to make composting work? No-earthworms tend to find an outdoor pile on their own once conditions are right.

Ready to put that compost somewhere good in your garden? Shop Raised Garden Beds and get your plants growing well.