Start with the two categories: browns and greens

Compost works because it mixes two types of material. Browns are dry, carbon-rich items like leaves, straw, shredded paper, and cardboard. Greens are wet, nitrogen-rich items like grass clippings, vegetable scraps, and coffee grounds. The pile needs both to break down properly — browns alone decompose slowly, and greens alone turn into a wet, smelly mess.

A working ratio is roughly three parts brown to one part green by volume, though the exact mix depends on what you have available and how fast you want decomposition to happen. If your pile smells like ammonia or looks slimy, add more browns. If it is not heating up or breaking down, add more greens.

Key Takeaways

  • Browns (leaves, cardboard, straw) and greens (grass, vegetable scraps, coffee grounds) must both go in for compost to work — aim for roughly three parts brown to one part green.
  • Meat, dairy, oils, and diseased plants do not belong in a home compost bin because they attract pests, spread disease, or take months longer to break down.
  • Shred or chop large items before adding them so they decompose faster and take up less space in the bin.
  • Layer browns and greens as you add material, and turn the pile every week or two if you want finished compost in two to three months.
  • Cooked food, pet waste, and glossy or treated paper will contaminate your compost or create safety problems.

Browns: dry materials that add carbon

Browns are the structural backbone of your pile. Dry leaves are the most common — collect them in fall and store them in bags to use year-round. Shredded newspaper and cardboard (remove tape and labels) break down well and are free if you save them. Straw and hay work, though hay may contain weed seeds. Wood chips and sawdust from untreated wood are acceptable, but use them sparingly because they take longer to decompose than other browns.

Shred or tear large pieces before adding them. A whole cardboard box takes months to break down; torn into strips, it decomposes in weeks. The same applies to leaves — run a lawn mower over a pile of leaves and they compress to a fraction of their original volume while breaking down faster.

Avoid treated wood, glossy cardboard, and paper with colored ink. Pressure-treated lumber contains chemicals that do not belong in soil. Glossy cardboard and magazines have coatings that slow decomposition. Plain newsprint and kraft paper are fine.

Greens: wet materials that add nitrogen

Greens are the engine of decomposition. Grass clippings, vegetable and fruit scraps, coffee grounds (with the filter), and tea bags all work. Plant trimmings from your garden, crushed eggshells, and nut shells are good additions. Seaweed and kelp are excellent if you have access to them.

Chop or crush greens before adding them — a whole apple takes longer to break down than one cut into quarters. Coffee grounds and tea bags can go in as-is. If you add a large amount of one type of green at once, bury it under a layer of brown so it does not attract flies.

Citrus peels, onion skins, and garlic scraps are fine in small amounts, though large quantities can slow decomposition and repel worms. Avoid adding too much of any single green in one day; spread additions over time so the pile stays balanced.

What never goes in: meat, dairy, and problem materials

Meat, fish, bones, and dairy products do not belong in a home compost bin. They take months to break down, smell terrible as they decompose, and attract rats, raccoons, and flies. Oils and fats have the same problems. If you have a commercial composting facility nearby that accepts these materials, you can take them there — but a backyard bin cannot handle them safely.

Diseased plants and weeds with seeds should stay out. If your tomato plant had blight or your squash had powdery mildew, composting it spreads the disease to your garden soil. Weeds that have gone to seed will survive the pile and sprout in your garden later. Throw these in the trash or burn them if local rules allow.

Pet waste — dog and cat feces — contains pathogens that home compost does not get hot enough to kill. Cooked food, even if it contains no meat or dairy, can attract pests and introduce salt or oils. Glossy or treated paper, plastic, and synthetic materials do not decompose and contaminate the finished compost.

How to layer and manage your pile

Add material in layers: a few inches of brown, then a few inches of green, then brown again. This keeps the pile balanced and speeds decomposition. Water each layer lightly as you build — the pile should feel like a wrung-out sponge, not dry and not soggy.

If you want finished compost in two to three months, turn the pile every week or two with a pitchfork or shovel, moving material from the outside to the center where it is hottest. If you are patient and do not mind waiting six months to a year, you can leave the pile alone and let it decompose passively — no turning needed.

In hot weather, the pile may heat up enough that you can feel warmth radiating from it. This is normal and means decomposition is happening fast. In cold weather, the pile slows down or stops; it will resume in spring.

Special materials: what works with caution

Pine needles and conifer leaves are acidic and decompose slowly, so use them sparingly. Sawdust from untreated wood is fine, but use no more than a thin layer at a time — it compacts and slows air flow. Charcoal from a grill should not go in; use only ash from a wood fire, and only a light dusting because ash is very alkaline.

Glossy or colored paper, even if it is not plastic-coated, may contain inks that do not break down well. Stick to plain newsprint, kraft paper, and cardboard. Shredded office paper works if it is not bleached white — the bleach slows decomposition.

Leaves from black walnut trees contain a chemical called juglone that kills many plants, so do not compost them if you plan to use the finished compost in a vegetable garden. Oak leaves are fine but take longer to break down because they are tough and waxy.

Frequently Asked Questions

Can I put bread and pasta in my compost?

Yes, but bury them under a layer of brown material so they do not attract pests. Bread, pasta, rice, and other cooked grains break down, but they draw rodents and insects if left exposed on the pile surface. Uncooked grains and flour work the same way — bury them.

What about weeds and grass with seeds?

Grass clippings from a mowed lawn are fine because the mower destroys most seeds. Weeds that have already gone to seed should go in the trash — home compost does not get hot enough to kill all seeds, and they will sprout in your garden. If you are unsure whether a weed has seeded, throw it out.

Can I compost paper towels and napkins?

Yes, as long as they are not bleached white and have no food residue that attracts pests. Plain paper towels and napkins break down quickly. If they are covered in grease or meat juice, throw them away instead — the grease slows decomposition and draws animals.

How do I know if my pile has the right balance?

If it smells like ammonia or looks slimy, add more browns and turn it. If it is not heating up or breaking down after a few weeks, add more greens. A healthy pile should feel warm in the center, smell earthy, and show visible breakdown of material within a few weeks.

Can I compost sawdust from treated wood?

No. Treated wood contains chemicals like copper or arsenic that do not break down and will contaminate your soil. Use only sawdust from untreated wood, and use it sparingly — it compacts easily and slows air flow in the pile.