The basics: what breaks down and what doesn't
You can compost most plant material from your kitchen and yard — fruit and vegetable scraps, coffee grounds, leaves, grass clippings, and wood chips all decompose in a home pile or bin. You cannot compost meat, dairy, oils, or diseased plants, because they either attract pests, create odor problems, or spread infection to your finished compost.
The rule is straightforward: if it came from a plant and has no oil or protein coating, it will break down. If it came from an animal or is heavily processed, it will not — or it will create problems while it tries.
What you compost depends partly on your setup. A sealed bin keeps out rodents better than an open pile, so you can be less strict about what goes in. A backyard pile in a residential area needs more care to avoid attracting rats and raccoons. Either way, the same materials decompose; the difference is how much trouble they cause along the way.
Key Takeaways
- Fruit and vegetable scraps, coffee grounds, eggshells, and plant trimmings are safe to compost in any home setup.
- Meat, fish, dairy, oils, and fats should never go in a home compost pile because they attract pests and create odor.
- Diseased plants and weeds with seeds will spread problems to your garden when you use the finished compost.
- Cooked food, bread, and grains can go in a sealed or buried pile but not an open backyard heap.
- Wood chips, cardboard, and paper break down slowly but improve soil structure and are worth adding in layers.
Vegetables, fruits, and plant scraps you should add
Vegetable and fruit scraps are the backbone of home composting. Carrot peels, apple cores, banana skins, lettuce leaves, broccoli stems, onion skins, and potato peels all decompose quickly. Coffee grounds and tea bags (remove the staple from tea bags first) add nitrogen and break down fast. Crushed eggshells add calcium and take longer to break down, but they do not cause problems while they wait.
Yard waste is equally valuable. Grass clippings, fallen leaves, plant stems, and flower trimmings all belong in the pile. If you mow your lawn, let the clippings dry slightly before adding them so they do not mat down and block air flow. Leaves are particularly good — they are carbon-rich and break down into a dark, crumbly material that improves soil.
Avoid adding diseased plants or plants that have been treated with pesticides. Diseased leaves and stems can survive the composting process and infect your garden when you spread the finished compost. Weeds with seeds are also risky — unless your pile gets hot enough to kill seeds (above 140 degrees Fahrenheit), you will spread weeds when you use the compost.
What to keep out: meat, dairy, and oils
Never add meat, fish, bones, or any animal product to a home compost pile. These materials attract rats, raccoons, and other pests, and they create strong odors as they decompose. Even a small amount of chicken skin or fish scraps can trigger a pest problem that takes weeks to resolve.
Dairy products — milk, cheese, yogurt, butter — also attract pests and create odor. Oils and fats, including cooking oil, salad dressing, and grease, slow decomposition and can make the pile smell rancid. Avoid adding them even in small amounts.
Pet waste should never go in a home compost pile. Dog and cat feces can carry parasites and pathogens that survive the composting process and contaminate your soil. This is true even if your pile reaches high temperatures.
Cooked food, bread, and grains: the middle ground
Cooked food, bread, pasta, and grains are technically compostable, but they come with conditions. Raw vegetables and fruit break down without attracting pests. Cooked food — especially if it contains oil or meat — attracts rodents and creates odor. Bread and grains ferment and smell bad as they decompose.
If you have a sealed bin or a pile that you bury food deep inside, you can add these materials. Bury cooked scraps at least eight inches down in the center of the pile, away from the edges. In an open backyard pile, skip them entirely. The smell and pest risk are not worth the small amount of compost you gain.
Moldy food is safe to compost — the mold is already breaking it down. Citrus peels and onions can go in, though some gardeners avoid large amounts of citrus because the acidity can slow decomposition slightly.
Paper, cardboard, and wood materials
Shredded newspaper, cardboard, and paper towels break down in a compost pile and add carbon, which balances the nitrogen from food scraps. Tear or shred cardboard into small pieces so it decomposes faster. Avoid glossy or colored paper — stick to plain newsprint and kraft cardboard.
Wood chips and sawdust from untreated wood are compostable, though they break down slowly. They are worth adding because they improve the final texture of your compost and help it hold water. Do not add sawdust from treated wood, plywood, or particle board — the glues and chemicals do not break down.
Paper with ink is safe — newspaper ink is soy-based and breaks down. Avoid adding wax-coated paper, plastic-lined paper, or anything with a plastic coating.
Yard waste that needs care
Grass clippings are excellent compost material, but they can mat down and block air flow if you add too much at once. Mix them with leaves or shredded paper to keep the pile loose. If you treat your lawn with herbicide or pesticide, let the clippings dry for a few weeks before composting, or skip them entirely.
Pine needles and conifer leaves are acidic and break down slowly, but they are safe to add. They will not harm your finished compost, though they may take months longer to decompose than softer leaves.
Branches and twigs thicker than a pencil take years to break down in a home pile. Chip them first if you have access to a chipper, or save them for a separate brush pile. Thin twigs and small branches are fine to add.
What happens if you add the wrong thing
If you accidentally add a small amount of meat or dairy, the pile will smell bad for a few days or weeks, but it will not ruin the entire batch. Cover the material with leaves or paper to reduce odor, and turn the pile if you can to speed decomposition. The smell will fade.
If you add diseased plants or weed seeds, you will not notice until you spread the compost in your garden months later. At that point, the disease or weeds will be in your soil. For this reason, it is worth being strict about what you add — the cost of removing diseased plants now is much lower than the cost of dealing with them in your garden later.
Pest problems are the most common issue. If you see rats or raccoons visiting your pile, stop adding food scraps and bury what you have already added. Switch to a sealed bin if you want to keep composting food waste, or stick to yard waste only in an open pile.
Frequently Asked Questions
Can I compost avocado pits and peach pits?
Yes. Pits and seeds break down eventually, though they take much longer than soft fruit. They will not harm your compost or your garden. If you want faster results, crush them first or skip them and add them to a separate pile.
What about glossy or colored paper?
Glossy paper and colored cardboard often contain chemicals or coatings that do not break down well. Stick to plain newsprint, kraft cardboard, and uncoated paper. When in doubt, leave it out.
Can I compost sawdust from my workshop?
Only if the wood is untreated. Sawdust from pressure-treated lumber, plywood, or particle board contains glues and chemicals that do not decompose and can contaminate your soil. If you are unsure whether the wood was treated, do not add the sawdust.
Is it okay to add weeds if I pull them before they go to seed?
Yes, as long as they have no seed heads. Once a weed has flowered or set seed, the seeds can survive composting. If you are not certain whether seeds are present, bury the weeds deep in the center of a hot pile, or skip them entirely.
Can I compost paper with ink on it?
Yes. Newspaper ink is soy-based and breaks down safely. Avoid wax-coated paper, plastic-lined paper, and anything with a plastic or glossy coating — those do not decompose.