What goes in your compost

You can compost most food scraps, yard waste, and paper products. The rule is straightforward: anything that was once alive and will break down naturally belongs in the bin. That includes fruit and vegetable scraps, coffee grounds, grass clippings, leaves, shredded paper, cardboard, and wood chips. Meat, dairy, oils, and diseased plants do not belong—they either attract pests, create odors, or spread disease to your finished compost.

The best compost comes from a mix of two types of material: greens (nitrogen-rich, wet materials like food scraps and fresh grass) and browns (carbon-rich, dry materials like leaves and shredded paper). A rough target is three parts brown to one part green by volume, though home composters do not need to be exact. The pile will work either way—it just takes longer if the ratio is off.

Key Takeaways

  • Fruit and vegetable scraps, coffee grounds, eggshells, and yard trimmings are safe to compost and break down quickly.
  • Meat, fish, dairy, oils, and fats should never go in a home compost bin because they attract rodents and create strong odors.
  • Diseased plants and weeds with seeds can spread problems to your garden, so keep those out of the pile.
  • Shredded paper, cardboard, and wood chips are valuable browns that balance wet food scraps and speed decomposition.
  • Cooked food, pet waste, and glossy or colored paper belong in the trash, not the compost.

Greens: the wet, nitrogen-rich materials

Greens are the fresh, moist materials that heat up your pile and feed the microbes doing the breakdown. Fruit and vegetable scraps are the most common: apple cores, banana peels, carrot tops, lettuce, squash, onion skins, and potato peels all go in. Coffee grounds and tea bags (remove the staple if it has one) add nitrogen and moisture. Eggshells break down slowly but are safe. Fresh grass clippings work, though let them dry for a day or two first if they are wet and matted—wet grass can compact and smell.

Plant-based kitchen waste is the safest bet. Avoid cooked food, because it can attract pests and create odors. Citrus peels, onions, and garlic are fine in small amounts, but large quantities can slow decomposition. If you have a lot of one type of scrap, spread it out over several days rather than dumping it all at once.

Browns: the dry, carbon-rich materials

Browns are the dry materials that add structure, prevent odors, and balance the moisture from greens. Dry leaves are the easiest source—rake them in fall and store them in bags to use year-round. Shredded paper and cardboard (no glossy coating or colored ink) work well. Sawdust and wood chips from untreated wood are fine. Straw and hay add bulk, though hay may contain weed seeds. Newspaper and plain cardboard boxes can be torn up and layered in.

The key is that these materials are dry and brown. Do not use glossy magazines, colored newspaper inserts, or cardboard with plastic tape or wax coating—the chemicals do not break down. Treated wood, plywood, and particle board also stay out because they contain glues and preservatives that contaminate the finished compost.

What to keep out of the bin

Meat, fish, poultry, and bones attract rats and raccoons and create strong odors as they rot. Dairy products like milk, cheese, and yogurt do the same. Oils, butter, and fatty foods slow decomposition and can make the pile smell rancid. Cooked food of any kind is risky because it often contains oil or meat. Pet waste (dog or cat feces) can harbor pathogens that survive composting and contaminate vegetables you grow later.

Diseased plants and weeds with mature seeds should not go in a home pile. A backyard compost pile does not usually reach the temperature needed to kill disease spores or weed seeds—that takes industrial composting. If you have a plant with powdery mildew, rust, or blight, throw it in the trash instead. The same goes for weeds that have gone to seed.

Avoid glossy or colored paper, magazines, and newspaper inserts. Pressure-treated wood, plywood, and sawdust from treated lumber contain chemicals that do not break down. Synthetic materials like plastic, rubber, and metal have no place in compost. Coal or charcoal ash can contain harmful substances—wood ash in small amounts is okay, but charcoal briquette ash is not.

How to handle problem materials

Some materials are safe but need care. Onions, garlic, and citrus peels can slow decomposition if added in large amounts, so chop them up and mix them in rather than piling them on top. Grass clippings mat down and can create a slimy layer—let them dry first or mix them with browns as you add them. Sawdust from untreated wood is fine, but use it sparingly because it is very dry and can absorb moisture from the pile.

If you have a lot of one material—say, a pile of leaves in fall or a bushel of tomato vines at harvest—add it gradually over a few weeks rather than all at once. This keeps the pile balanced and prevents it from becoming too wet or too dry. If your pile starts to smell like ammonia or rotten eggs, it has too many greens; add more browns and turn it to add air.

Speeding up decomposition with the right mix

A pile that is roughly three parts brown to one part green by volume will heat up and break down in two to four months during warm weather. If you want faster results, chop or shred materials into smaller pieces—smaller pieces have more surface area for microbes to work on. Turn the pile every week or two to add air, which speeds decomposition significantly.

If you are building a new pile, layer browns and greens as you go: a few inches of brown, then a few inches of green, then brown again. This creates a more even mix than dumping all the browns in first. Keep the pile as moist as a wrung-out sponge—if it is too dry, decomposition slows; if it is too wet, it smells and attracts pests. In dry weather, water it lightly. In wet weather, cover it with a tarp or lid to shed excess rain.

Finished compost and what to do with it

After two to six months (depending on temperature, pile size, and how often you turn it), the materials will have broken down into dark, crumbly, earthy-smelling compost. It should look like soil and fall apart in your hand. Use it to amend garden beds, mix it into potting soil, or spread it around trees and shrubs. A layer two to three inches thick worked into the top few inches of soil improves drainage, adds nutrients, and helps soil hold water.

If your pile still has recognizable chunks of material, let it sit longer or move it to a new bin and turn it again. Partially finished compost will still improve soil, but fully finished compost is easier to use and looks more professional if you are spreading it in visible areas.

Frequently Asked Questions

Can I compost bread, pasta, and rice?

Cooked bread, pasta, and rice should not go in a home compost bin because they attract rodents and can create odors. Raw grains are safer but still risky—they can draw pests. If you want to compost them, bury them deep in the center of the pile where they are less likely to attract animals.

What about paper towels and napkins?

Plain paper towels and napkins are fine to compost—they are just paper. Avoid paper towels or napkins that have been in contact with meat, oil, or grease. If they are clean and dry, tear them up and add them as browns.

Can I put weeds in the compost?

Weeds without seeds are safe. If the weeds have gone to seed or have roots that spread (like bindweed or quackgrass), throw them in the trash instead. A home compost pile does not get hot enough to kill seeds or aggressive root systems.

Is it okay to compost sawdust from my workshop?

Sawdust from untreated wood is fine in small amounts mixed with other materials. Sawdust from treated lumber, plywood, or particle board should not go in compost because it contains glues and preservatives. If you are unsure whether the wood was treated, leave it out.

What do I do if my compost smells bad?

A rotten-egg or ammonia smell means the pile has too many greens and not enough air. Add more browns, turn the pile to add oxygen, and let it dry out a bit. If it smells like rotting meat or fish, something inappropriate got in—dig it out and remove it.