What goes in a compost bin

A compost bin breaks down organic material into soil-like matter through the work of bacteria, fungi, and insects. What you can add depends on whether you're composting at home or using a municipal program, but the basic rule is straightforward: add things that were once alive and will rot.

The easiest items to compost are brown materials (dry, carbon-rich) and green materials (wet, nitrogen-rich). Browns include dry leaves, shredded paper, cardboard, straw, and wood chips. Greens include grass clippings, vegetable scraps, coffee grounds, tea bags, and plant trimmings. A working bin needs both — roughly three parts brown to one part green — so the pile doesn't turn into a wet, smelly mess.

Food scraps are where most home composters start. Vegetable peels, fruit cores, eggshells, coffee grounds, and tea leaves all break down in a few weeks to a few months. Cooked food, meat, fish, dairy, and oils do not belong in a home bin because they attract rats and create odor problems that take months to resolve. If you have access to a municipal or commercial compost program, many of these items are accepted because industrial composting reaches higher temperatures and runs for longer periods.

Key Takeaways

  • Vegetable scraps, fruit waste, coffee grounds, and dry leaves are safe for any home compost bin and break down in weeks to months.
  • Meat, fish, dairy, oils, and cooked food should not go in a home bin because they attract pests and create odor, but many municipal programs accept them.
  • Diseased plants, weeds with seeds, and pet waste do not belong in any compost system because they can spread pathogens or contaminate soil.
  • Glossy paper, treated wood, synthetic materials, and charcoal ash will not break down and should go in the trash instead.
  • Shredded newspaper and cardboard are acceptable, but avoid paper with colored inks or plastic coatings.

Brown materials that compost well

Browns are the carbon backbone of a compost pile. Dry leaves are the most common — rake them in fall and store them in a bag to use year-round. Shredded newspaper works if it's black ink only; avoid glossy inserts and colored sections. Cardboard boxes, paper bags, and paper towel tubes all break down, but remove tape and labels first.

Wood chips, sawdust, and untreated wood shavings compost slowly but add structure to the pile. Straw (not hay, which contains seeds) works well. Avoid treated wood, plywood, and anything with a glossy or plastic coating — these don't break down and can leach chemicals into your finished compost.

Green materials that compost well

Greens are nitrogen-rich and speed up decomposition. Grass clippings work, but use them sparingly because they mat down and create odor — mix them with browns or let them dry first. Vegetable and fruit scraps are the easiest entry point: carrot peels, apple cores, lettuce leaves, broccoli stems, and banana peels all disappear in a few weeks.

Coffee grounds and tea bags (remove the staple from tea bags) add nitrogen and moisture. Plant trimmings from houseplants and gardens work fine. Fresh manure from herbivores — horse, cow, or chicken — can be added if you're willing to wait longer for the pile to finish, because it needs time to cool and age before the compost is safe to use on food gardens.

What not to compost at home

Meat, fish, poultry, and bones attract rats and raccoons and create smell that can take months to fade. Dairy products, oils, butter, and grease do the same. Cooked food of any kind should stay out — even a small amount of cooked rice or pasta can draw pests. Pet waste (dog or cat feces) contains pathogens that home composting temperatures don't kill, so it's unsafe for food gardens.

Diseased plants and weeds with mature seeds should not go in a home bin because the pile may not get hot enough to kill the disease or germinate the seeds. Glossy paper, magazines, and colored cardboard contain inks and coatings that don't break down. Charcoal ash (from a grill) and coal ash contain substances that can harm plants; wood ash from a fireplace is acceptable in small amounts if your soil isn't already alkaline.

Synthetic materials — plastic, rubber, treated fabrics — do not compost. Pressure-treated wood, plywood, and composite lumber contain chemicals that leach into soil. Sawdust from treated wood is also off-limits. Glossy or waxed cardboard, like takeout containers, should go in recycling or trash instead.

What municipal and commercial programs accept

If your city or county runs a compost collection program, the rules are usually broader than home composting. Most accept meat, fish, bones, dairy, oils, and cooked food because industrial facilities reach 140°F or higher and maintain that temperature for weeks. This kills pathogens and breaks down materials that would rot slowly or attract pests at home.

Check your local program's website or call to confirm what they take — rules vary by facility. Some accept pet waste, diseased plants, and yard trimmings; others do not. Many programs reject glossy paper, plastic bags, and treated wood for the same reasons home composters should. If you don't have a municipal program nearby, search for "commercial compost near me" or check Earth911.com to find a drop-off location.

How to prepare materials before composting

Chop or shred larger items so they break down faster. A whole apple takes longer than apple slices; a whole cardboard box takes longer than torn pieces. Wet materials like grass clippings should be mixed with dry materials or spread out to dry slightly, or they'll compact and smell.

Remove labels, tape, and stickers from cardboard and paper. Tear out plastic windows from envelopes. If you're adding manure, let it age in a separate pile for a few months before mixing it into your main compost, or add it only to compost you won't use on vegetables for at least a year.

Signs your compost is ready to use

Finished compost looks like dark, crumbly soil and smells earthy, not sour or rotten. You should not see recognizable food scraps or leaves — everything should be broken down. This usually takes three to six months in an active bin where you turn the pile weekly, or six to twelve months if you just add material and let it sit.

If your pile smells bad, it's too wet or has too much green material — add dry leaves or shredded paper and turn it. If it's not heating up or breaking down, it may be too dry or need more green material. A working pile should feel warm in the center when you push your hand into it.

Frequently Asked Questions

Can I compost paper towels and napkins?

Yes, plain white paper towels and napkins break down in a compost bin. Avoid ones with printed patterns or bleach-bright whiteness, which may contain dyes or chemicals. Shred them first so they break down faster.

What about citrus peels and onion skins?

Citrus peels and onion skins compost fine, though citrus takes longer because of the oils. Add them in moderation — a few peels per week is normal, but a whole bag of orange peels can slow decomposition. Garlic and onion skins are safe and break down quickly.

Can I put weeds in my compost?

Weeds without seeds are safe. If the weeds have gone to seed, leave them out — home compost usually doesn't get hot enough to kill seeds, and you'll spread them when you use the finished compost. Diseased plants should also stay out because the disease may survive.

Is it okay to compost sawdust from my workshop?

Sawdust from untreated wood is fine in small amounts mixed with other materials. Sawdust from pressure-treated wood, plywood, or composite lumber should not be composted because it contains chemicals that don't break down and can contaminate soil.

What should I do with compost that smells bad?

Bad smell usually means too much moisture or too many greens. Stop adding wet materials, mix in dry leaves or shredded paper, and turn the pile if you can. If it smells like ammonia, add more browns. If it smells like rotten eggs, it's too wet — spread it out or add dry material and let air in.