What goes into your compost bin

You can compost most plant material from your kitchen and yard. Fruit and vegetable scraps, coffee grounds, tea bags, grass clippings, leaves, small branches, and plant trimmings all break down into usable compost. Cardboard, shredded paper, and untreated wood chips also decompose well. The key is balancing "brown" materials (carbon-rich items like dried leaves and paper) with "green" materials (nitrogen-rich items like food scraps and fresh grass).

The ratio matters more than the specific items. A working compost pile needs roughly three parts brown to one part green by volume. If your pile smells like ammonia or looks slimy, you have too much green. If it is not heating up or breaking down, you need more green material mixed in.

Key Takeaways

  • Fruit, vegetable scraps, coffee grounds, grass clippings, leaves, and cardboard all compost successfully in a home bin.
  • Meat, dairy, oils, diseased plants, and pet waste should never go into home compost because they attract pests or create health hazards.
  • Balance brown materials (leaves, paper, wood chips) with green materials (food scraps, grass) at roughly a 3-to-1 ratio by volume.
  • Compost is ready to use when it looks like dark crumbly soil and no longer smells like rotting food, usually six months to two years depending on method and climate.

Foods and kitchen waste you can compost

Vegetable and fruit scraps are the foundation of most home compost. Onion skins, carrot tops, apple cores, banana peels, lettuce leaves, and citrus rinds all work. Coffee grounds and tea bags (remove the staple from tea bags first) add nitrogen and break down quickly. Eggshells take longer to decompose but add calcium. Stale bread, cooked grains, and pasta can go in, though they may attract pests if not buried under brown material.

Avoid putting meat, fish, bones, dairy products, oils, or fats into a home compost bin. These materials attract rats, raccoons, and flies. They also create odor problems and can harbor harmful bacteria. If you want to compost these items, you need a specialized hot composting system or a commercial composting program in your area.

Yard waste that composts well

Grass clippings, fallen leaves, plant trimmings, and small branches are ideal for compost. Shred or chop larger materials so they break down faster. Leaves are especially valuable because they are carbon-rich and free. If you collect leaves in fall, store them in a bin or bag and add them gradually through the year to balance your green materials.

Do not compost plants that have been treated with pesticides or herbicides, or plants showing signs of disease like powdery mildew or fungal infections. Diseased material can survive the composting process and spread problems to your garden. Weeds with mature seed heads should also stay out—the compost may not get hot enough to kill the seeds.

Paper and cardboard in your compost

Shredded newspaper, cardboard boxes, paper bags, and plain cardboard all compost. Tear or shred them into smaller pieces so they break down faster. Cardboard is especially useful because it is bulky, carbon-rich, and free. Remove tape, plastic windows, and plastic-coated liners before adding cardboard to your bin.

Glossy paper, colored paper with heavy inks, and paper with plastic coating should not go in. Newspaper is fine—modern newspaper inks are soy-based and safe. Avoid paper that has been treated with wax or plastic, or paper from magazines with heavy color printing.

Materials that should never be composted

Pet waste, including dog and cat feces, should never go into home compost. It can contain harmful pathogens that survive the composting process. Human waste also belongs in a septic system or sewer, not a compost bin. Diseased plants, invasive weeds with seeds, and plants treated with chemicals all pose problems. Meat, fish, bones, dairy, oils, and fats attract pests and create odor.

Synthetic materials like plastic, rubber, and treated wood do not break down in a home compost bin. Charcoal ash from a grill should stay out because it contains substances that slow decomposition. Wood ash from a fireplace can go in small amounts, but it raises pH and should be used sparingly. Sawdust from treated lumber is toxic and must be avoided.

How to know when compost is ready to use

Finished compost looks like dark, crumbly soil. You should not be able to identify the original materials. It smells earthy, not like rotting food or ammonia. When you squeeze a handful, it holds together briefly but crumbles apart easily. The pile has stopped heating up and shrunk to roughly one-third its original volume.

The time it takes depends on your method, climate, and how often you turn the pile. A hot composting system with regular turning can produce finished compost in two to three months. A passive pile in a cool climate may take a year or longer. You can use partially finished compost as a mulch layer, but fully decomposed compost is better for mixing into garden beds or potting soil.

Frequently Asked Questions

Can I compost onions and garlic?

Yes, onion and garlic scraps compost fine. They may repel some pests while decomposing, which is actually helpful. Avoid adding huge quantities at once because they can create odor, but normal kitchen scraps are no problem.

What about pine needles and evergreen branches?

Pine needles and evergreen material compost very slowly because they are dense and acidic. You can add small amounts, but they will take much longer to break down than leaves or grass. Shred them first to speed the process.

Can I compost sawdust from my workshop?

Only sawdust from untreated wood. Sawdust from pressure-treated lumber, plywood, or painted wood contains chemicals and should never be composted. If you are unsure whether the wood was treated, leave it out.

Is it okay to compost glossy paper or cardboard with printing?

Plain cardboard and newspaper are fine. Glossy paper, heavily printed magazines, and cardboard with plastic coating should be avoided. Modern newspaper ink is soy-based and safe, but shiny magazine paper often contains chemicals that do not break down well.

What if my compost smells bad?

A rotten or ammonia smell means too much green material or too much moisture. Mix in dry brown material like shredded leaves or cardboard and turn the pile. If it smells like sulfur, it may be too wet—add more brown material and improve drainage or aeration.