What Goes Into Compost and What Doesn't
Not everything that rots belongs in your compost bin. The things that break down fastest and create the best finished compost are green materials (nitrogen-rich: grass clippings, vegetable scraps, coffee grounds) and brown materials (carbon-rich: dry leaves, shredded paper, wood chips). The things that cause problems are meat, dairy, oils, diseased plants, and treated wood — they either attract pests, kill the microbes doing the work, or take years to decompose.
The rule is straightforward: if it came from a plant or is paper or cardboard, it usually belongs in the bin. If it came from an animal or is treated with chemicals, it usually doesn't. The exceptions matter because they determine whether your pile smells, whether rats move in, and whether your finished compost is safe to use on vegetables.
Key Takeaways
- Vegetable scraps, fruit peels, grass clippings, leaves, and shredded paper all break down well and should go in your bin.
- Meat, fish, dairy, oils, and fats attract rodents and should never be added, even in small amounts.
- Diseased plants and weeds with seeds can spread problems to your garden, so keep them out.
- Wood chips and sawdust from untreated wood are fine, but pressure-treated lumber and plywood contain chemicals that poison the finished compost.
- Glossy or colored paper, pet waste, and coal or charcoal ash do not belong in home compost systems.
Green Materials That Speed Up Decomposition
Green materials are wet, nitrogen-rich, and break down quickly. They heat up your pile and feed the bacteria and fungi doing the work. The best ones are fresh grass clippings, vegetable and fruit scraps (peels, cores, wilted lettuce, carrot tops), coffee grounds and tea bags, plant trimmings, and fresh manure from herbivores like horses, chickens, or rabbits.
Vegetable scraps are the easiest to remember: anything you would throw away from meal prep or leftovers goes in. Citrus peels, onion skins, apple cores, and overripe bananas all work. Avoid putting in large amounts of one thing at once — a pile of just citrus peels can slow decomposition because they are acidic and dense. Mix them with brown materials and other greens.
Grass clippings are excellent if they come from a lawn that has not been treated with herbicides or pesticides in the past few months. If you use weed killer or fertilizer on your lawn, let the grass dry out and break down on the ground for a season before composting it, or skip it entirely. Clippings from a recently treated lawn will kill the microbes in your pile.
Brown Materials That Add Structure and Carbon
Brown materials are dry, carbon-rich, and decompose slowly. They create air pockets, prevent the pile from becoming a wet mat, and feed the microbes over time. The best ones are dry leaves, shredded paper and cardboard, wood chips, sawdust, straw, and hay.
Dry leaves are free and abundant in fall. Shred them with a mower or by hand — smaller pieces decompose faster. Cardboard and paper should be plain: no glossy coatings, no colored inks, no tape or stickers. Shred it into strips so it breaks down faster. Newspaper is fine; magazines and junk mail are not because of the inks and coatings.
Wood chips and sawdust from untreated wood are safe. Untreated means no pressure treatment, no paint, no stain. If you are unsure whether wood has been treated, do not compost it. Pressure-treated lumber contains arsenic or copper compounds that will end up in your finished compost and make it unsafe for vegetable gardens.
Animal Products and Oils to Keep Out
Meat, fish, bones, dairy, eggs, and oils should never go in a home compost bin. They attract rats, raccoons, and flies. They also decompose slowly and create odors that upset neighbors. Even small amounts — a chicken bone, a spoonful of yogurt, a splash of cooking oil — are enough to bring pests.
If you have a commercial composting facility nearby that accepts food waste, they can handle meat and dairy because their piles reach temperatures above 140°F, which kills pathogens and deters pests. Home bins rarely get that hot. Stick to plant-based scraps.
Grease and cooking oil coat other materials and slow decomposition. They also create an environment where anaerobic bacteria thrive, which produces methane and foul smells. Wipe greasy pans with a paper towel before washing them, and throw the towel in the trash or burn it.
Plants and Seeds You Should Exclude
Diseased plants — those with powdery mildew, blight, root rot, or fungal infections — should not go in your bin. The disease can survive the composting process and spread to your garden when you use the finished compost. If a plant is visibly sick, throw it in the trash.
Weeds with mature seeds should also stay out. If your compost pile does not reach 140°F consistently, the seeds will survive and germinate in your garden. Weeds without seeds are fine. If you are unsure whether a weed has set seed, err on the side of caution and throw it away.
Invasive plants like bindweed, bermuda grass, or morning glory should go in the trash, not the compost, because even small root fragments can regrow. The same applies to plants treated with herbicides — wait at least a season before composting them.
Paper, Cardboard, and Wood Products
Plain paper and cardboard break down well and add carbon to your pile. Newspaper, paper bags, paper towels, and cardboard boxes are all safe. Shred them into strips so they decompose faster and mix them with greens so they do not mat down and block air flow.
Avoid glossy paper, colored cardboard, and anything with plastic coating. Magazines, junk mail, takeout boxes with plastic windows, and wax-coated paper do not belong. The inks and coatings either do not decompose or leach chemicals into your compost.
Sawdust and wood chips from untreated wood are fine in small amounts. Large amounts of sawdust can slow decomposition because it is very fine and compacts easily. Mix it with greens and coarser brown materials. Never use sawdust from pressure-treated lumber, plywood, or particle board — these contain glues and chemicals that will contaminate your finished compost.
Ash, Pet Waste, and Other Problem Materials
Wood ash from a fireplace or wood stove can go in compost in small amounts — a light dusting, not a bucket. It adds potassium and raises the pH of acidic piles. Coal ash and charcoal ash should not go in because they contain substances that slow decomposition and can harm plants.
Pet waste — dog or cat feces — should never be composted in a home system. It contains pathogens that survive normal composting temperatures and can contaminate vegetables. Horse, chicken, and rabbit manure are safe because those animals are herbivores and their waste is less likely to carry human pathogens.
Synthetic materials like plastic, rubber, metal, and glass obviously do not belong. Less obvious: glossy or coated paper, treated wood, and anything with adhesive tape. If you are unsure whether something is compostable, assume it is not and throw it away. A few items in the trash are better than a contaminated pile.
Frequently Asked Questions
Can I put bread, pasta, and cooked food in my compost?
Cooked food and bread can go in, but they attract pests just like meat and dairy do. If your bin has a tight-fitting lid and you bury food scraps deep in the pile, you may avoid problems. If you have rats or raccoons in your area, skip cooked food and stick to raw vegetable scraps.
What about coffee filters and tea bags?
Coffee filters and paper tea bags are fine — they break down quickly. Remove any staples from tea bags first. If the tea bag is made of plastic mesh or has a plastic coating, throw it away instead.
Can I compost pine needles and evergreen branches?
Pine needles and evergreen branches decompose very slowly because they are acidic and tough. Small amounts mixed in are okay, but do not add large quantities. They will sit in your pile for years without breaking down.
Is it safe to compost weeds if I remove the seeds?
Yes, if you are certain there are no seeds. The problem is that weed seeds are tiny and straightforward to miss. If you are not confident, throw the weeds away. It is not worth risking a garden full of weeds.
Can I put dryer lint in my compost?
Lint from a dryer that runs on natural fibers — cotton, wool, linen — can go in. Lint from synthetic fabrics like polyester does not break down. If you are unsure what your clothes are made of, skip the lint.