What belongs in your compost bin

A compost bin breaks down organic material into dark, crumbly soil you can use in gardens and potted plants. The things that decompose fastest are green materials (nitrogen-rich) and brown materials (carbon-rich), layered together. You need both types working together—greens alone turn slimy, browns alone decompose slowly.

Green materials include fruit and vegetable scraps, fresh grass clippings, plant trimmings, coffee grounds and tea bags (remove staples first), and fresh manure from herbivores like horses, rabbits, or chickens. Brown materials include dry leaves, shredded newspaper and cardboard, straw, wood chips, sawdust from untreated wood, and paper towels. The ideal mix is roughly three parts brown to one part green by volume, though home composters rarely measure precisely and still get results.

Key Takeaways

  • Fruit and vegetable scraps, grass clippings, leaves, and shredded paper all break down in a compost bin and should be layered together.
  • Meat, fish, dairy, oils, and diseased plants should never go in a home compost bin because they attract pests or spread disease.
  • Cooked food, pet waste, and glossy or colored paper will not decompose properly or may introduce harmful bacteria.
  • A working bin needs both green materials (grass, food scraps) and brown materials (leaves, cardboard) to heat up and break down efficiently.

What to keep out of your compost bin

Never add meat, fish, bones, or any animal product except herbivore manure. These attract rats, raccoons, and flies, and they smell as they rot. The same goes for dairy, oils, fats, and grease—they create odor and draw pests. Cooked food of any kind should stay out, even if it contains no meat, because the cooking process changes how it breaks down and can harbor harmful bacteria.

Do not compost diseased plants, plants treated with pesticides, or weeds that have gone to seed. Disease spreads through compost and survives the decomposition process. Pet waste (dog or cat feces) contains pathogens that home compost does not get hot enough to kill. Glossy or colored paper, magazines, and cardboard with plastic tape or wax coating will not break down or will release chemicals as they do.

Materials that need special handling

Grass clippings are green material and belong in compost, but only if the lawn was not treated with herbicide or pesticide within the past few weeks. If you use lawn chemicals, let the grass dry and decompose separately, or skip it. Sawdust and wood chips are excellent brown material, but only from untreated wood—sawdust from pressure-treated lumber or plywood contains chemicals that will contaminate your finished compost.

Citrus peels, onion skins, and garlic break down fine, but add them sparingly because they take longer to decompose and can slow the whole pile. Bread, pasta, and grains will compost but attract pests more readily than vegetable scraps, so bury them deep in the center of the pile. Pine needles and walnut leaves are acidic and decompose slowly; they can go in but will not speed things up.

How to layer materials for faster breakdown

Start with a 4- to 6-inch layer of brown material on the bottom—shredded leaves or cardboard work well. Add a 2- to 3-inch layer of green material on top (grass clippings, food scraps, fresh plant trimmings). Repeat this pattern as you add material. Water each layer lightly so it is damp but not soggy, like a wrung-out sponge. This alternating pattern keeps air flowing through the pile and prevents the greens from matting down and turning anaerobic.

Every week or two, turn the pile with a garden fork or shovel if you want faster compost (ready in 2 to 3 months), or leave it undisturbed if you are willing to wait 6 to 12 months. Turning speeds decomposition by introducing oxygen, but it is not required. A bin that sits still will still produce finished compost; it just takes longer.

Signs your bin has the wrong mix

If your compost smells like ammonia or rotten eggs, you have too much green material and not enough air. Add brown material (leaves or shredded paper) and turn the pile. If it smells like nothing and is not heating up or breaking down after several weeks, you likely have too much brown material or not enough moisture. Add green material and water lightly.

If you see flies or smell rot, you probably added meat, dairy, or cooked food. Remove the offending material if you can find it, bury future food scraps deeper in the pile, and consider adding a layer of brown material on top to discourage insects. A properly balanced bin should smell earthy, like forest floor, not foul.

When to stop adding and let it finish

Once your bin is full or you decide to stop feeding it, stop adding new material and let the pile sit. Finished compost looks dark brown or black, crumbly, and smells like soil. You should not be able to identify individual scraps. This usually takes 2 to 3 months if you turn the pile regularly, or 6 to 12 months if you leave it alone.

You can use partially finished compost in the garden—it will continue breaking down in the soil—but sift out any large pieces first. Some people keep two bins so they can fill one while the other finishes, or they add new material to the top of a bin while harvesting finished compost from the bottom.

Frequently Asked Questions

Can I put paper towels and napkins in my compost?

Yes, plain white paper towels and napkins break down fine and count as brown material. Avoid paper towels that have been used with meat, oils, or chemicals. Colored or printed napkins are usually safe too, but check that the ink is soy-based or plant-based rather than petroleum-based.

What about eggshells and coffee filters?

Eggshells decompose slowly but do belong in compost—they add calcium. Coffee filters and the grounds inside are both fine. Remove any staples from tea bags before adding them, or use loose tea leaves instead.

Can I compost bread and pasta?

Yes, but bury them in the center of the pile where they are less likely to attract pests. They count as green material and will break down, though they take longer than vegetable scraps.

Is it safe to use compost made from food scraps in a vegetable garden?

Yes, as long as you did not add meat, dairy, or diseased plants. Finished compost is safe for vegetables, herbs, and any other plants. If you are concerned, let the compost sit for a few months after it appears finished before using it on edibles.

What if my compost bin is in a small space and I cannot turn it?

You do not have to turn your pile. It will still decompose—just more slowly, usually taking 6 to 12 months instead of 2 to 3. Keep the material damp and layered, and it will work on its own.