The Basic Rule: Brown and Green, Not Meat or Oil
You can compost most plant material — leaves, grass clippings, vegetable scraps, coffee grounds, and shredded paper. You cannot compost meat, fish, dairy, oils, fats, or diseased plants. The reason is straightforward: materials that break down slowly or attract pests belong in the trash, while plant matter rots reliably and feeds your soil.
The fastest way to remember what works is to think in two categories. Green materials are nitrogen-rich and wet: fruit and vegetable scraps, grass clippings, plant trimmings, coffee grounds, and tea bags. Brown materials are carbon-rich and dry: leaves, shredded paper, cardboard, straw, and wood chips. A working pile needs both. Too much green and it smells like rot; too much brown and nothing happens.
Key Takeaways
- Compost all fruit and vegetable scraps, grass clippings, leaves, coffee grounds, and shredded paper or cardboard without hesitation.
- Never compost meat, fish, bones, dairy products, oils, fats, or pet waste, because they attract pests or create odor problems.
- Diseased plants, weeds with seeds, and treated wood should stay out of your pile because they spread problems to your garden.
- A balanced pile needs roughly three parts brown material to one part green material by volume.
- If you are unsure about an item, err on the side of throwing it away rather than risking a pest problem.
Vegetables, Fruits, and Plant Scraps You Can Compost
All raw fruit and vegetable scraps break down reliably. This includes apple cores, banana peels, carrot tops, lettuce leaves, onion skins, potato peels, and citrus rinds. Cooked vegetables also work, though they break down more slowly. Avoid cooked vegetables if your pile is in a yard where raccoons or rats are active, because the smell can draw them in.
Coffee grounds and tea bags are excellent additions. Leave the tea bag in if it is paper or plant-based; remove it if it is plastic mesh. Eggshells take months to break down but do eventually decompose, so they are worth adding if you have patience. Crushed shells speed the process.
Grass clippings and plant trimmings from your garden are ideal, as long as the plants were healthy. Leaves, whether fresh or dried, are among the best brown materials you can add — they are free, abundant, and break down into rich compost.
Paper, Cardboard, and Wood Materials That Work
Shredded newspaper, plain cardboard, and paper bags all compost. Tear or shred them into pieces smaller than your hand so they break down faster. Avoid glossy paper, colored inks, and cardboard with plastic tape or wax coating. Plain kraft paper and newsprint are safe.
Straw and hay are excellent brown materials. Wood chips and sawdust from untreated wood also work, though they take longer to decompose than leaves or paper. Never use sawdust or chips from pressure-treated wood, which contains chemicals that will contaminate your compost and your garden.
What to Keep Out: Meat, Dairy, and Oils
Meat, fish, bones, and any animal products except eggshells attract rats, raccoons, and flies. They also create strong odors that upset neighbors. The same rule applies to dairy — milk, cheese, yogurt, and butter all draw pests and smell terrible as they rot. Oils, grease, and fats coat other materials and slow decomposition, plus they attract animals.
If you have a commercial composting facility nearby that accepts food scraps, you can take meat and dairy there instead. Most home compost piles cannot handle them safely. If you are unsure whether your local program accepts these items, call the facility before you bring anything in.
Plants and Garden Material to Avoid
Do not compost plants that were diseased or infested with pests. Powdery mildew, blight, and fungal infections can survive the composting process and spread to your garden when you use the finished compost. The same applies to weeds that have already gone to seed — the seeds often survive and you end up spreading weeds instead of preventing them.
Diseased leaves from trees (like oak wilt or anthracnose) should go in the trash. Invasive plants like bindweed or Japanese knotweed should also be thrown away, not composted, because even small fragments can regrow. When in doubt, throw it out.
Pet Waste and Treated Materials
Dog and cat waste should never go in a home compost pile. Pet feces carry pathogens that home composting temperatures do not reliably kill, and these pathogens can survive in the finished compost and contaminate your vegetables. Commercial facilities with higher heat can sometimes handle pet waste, but home piles cannot.
Treated wood, pressure-treated lumber, and plywood all contain chemicals or glues that leach into compost. Charcoal and coal ash also belong in the trash — they contain substances that harm plants. Wood ash from a fireplace or wood stove is safe in small amounts, but do not add more than a light dusting.
Items That Slow Down or Complicate Composting
Bread, pasta, rice, and cooked grains will compost, but they attract pests just like meat does. If your pile is in an open bin or exposed location, skip them. If your pile is in a sealed tumbler or buried deep in a fenced yard, they are usually fine.
Nuts and seeds take a long time to break down and may sprout if they are not fully buried. Avocado pits and peach pits are so hard they barely decompose in a home pile — throw them away. Onions and garlic can repel worms, so use them sparingly. Glossy or colored paper, plastic bags, and synthetic materials do not belong in any compost pile.
Frequently Asked Questions
Can I compost moldy food?
Yes. Mold is a sign that decomposition is already happening, so moldy fruit, bread, or vegetables are perfect for compost. The mold will break down along with the food.
What about sawdust from my woodworking?
Only if the wood was untreated. Sawdust from pressure-treated lumber, plywood, or painted wood contains chemicals that will contaminate your compost. If you are unsure whether the wood was treated, do not use the sawdust.
Can I compost paper with ink on it?
Newspaper and plain black ink are safe. Glossy magazines, colored inks, and thermal paper (like receipts) should go in the trash. When in doubt, shred it and add it to your pile — a small amount of ink will not hurt.
Is it okay to compost weeds?
Only if they have not gone to seed. If the weeds are green and young, they will break down fine. If they have flowers or seed heads, pull them out and throw them away instead.
How do I know if my pile has too much green material?
A pile that smells like ammonia or rotten eggs has too much green. Add dry leaves, shredded paper, or cardboard to balance it out. A good rule is three parts brown to one part green by volume.