Start with the right location and container

A compost pile works best in a spot that gets partial shade and sits on bare soil or grass, not concrete. Partial shade keeps the pile from drying out too fast in summer while still letting it warm up enough to break down materials. Bare soil matters because it lets earthworms and microbes move in from below—these creatures do much of the decomposition work for you.

You can build a compost pile three ways: in an open heap with no container, inside a wooden bin you build yourself, or in a purchased plastic or metal bin. An open heap is free and takes up more space but needs turning more often. A wooden bin (made from untreated wood or wire mesh) costs $20 to $50 in materials and keeps the pile neater. A purchased bin runs $50 to $200 and takes up the least space, though it may slow decomposition slightly because air moves through it less freely.

If you live in a neighborhood with rules about yard appearance, a bin with a lid is your best choice. If you have the space and don't mind the look, an open pile or straightforward wooden frame works just as well and often faster.

Key Takeaways

  • A compost pile needs a mix of "brown" materials (dry leaves, shredded paper, straw) and "green" materials (grass clippings, vegetable scraps, coffee grounds) in roughly equal amounts by volume.
  • The pile should be at least 3 feet wide and 3 feet tall to heat up enough for fast decomposition, though smaller piles still work—they just take longer.
  • Turning the pile every one to two weeks speeds decomposition to 2 to 3 months; leaving it untouched takes 6 to 12 months but requires no work.
  • Keep the pile as moist as a wrung-out sponge; if it smells like ammonia or rotten eggs, it is too wet or has too many greens.
  • Finished compost looks dark brown, crumbly, and earthy and breaks apart easily in your hand.

Layer browns and greens in the right ratio

Brown materials are dry and carbon-rich: fallen leaves, shredded newspaper or cardboard, straw, wood chips, and sawdust. Green materials are wet and nitrogen-rich: grass clippings, vegetable and fruit scraps (no meat, dairy, or oils), coffee grounds, tea bags, and plant trimmings. The pile decomposes fastest when you mix them roughly half and half by volume—not by weight.

Start your pile by laying down a 4- to 6-inch layer of browns on the ground. This lets air flow underneath. Then add a 4- to 6-inch layer of greens. Keep alternating until your pile is at least 3 feet tall and 3 feet wide. A pile smaller than this won't heat up enough to decompose quickly, though it will still work over time.

If you don't have enough material to build the whole pile at once, that's fine—add to it as you collect scraps. Just keep the ratio roughly balanced. If you add mostly grass clippings one week and mostly leaves the next, the pile will still work, but it may smell bad or decompose unevenly.

Water and turn the pile to speed decomposition

The pile needs to stay as moist as a wrung-out sponge—damp but not dripping. If it's too dry, decomposition slows to a crawl. If it's too wet, it smells like ammonia or rotten eggs and attracts flies. Check the moisture by squeezing a handful of pile material: a few drops of water should come out, but not a stream.

Water the pile when the top few inches feel dry, usually once a week in warm weather and less often in cool or rainy weather. Use a hose or watering can and soak it until water drips from the bottom.

Turning the pile every one to two weeks speeds decomposition to 2 to 3 months. Use a garden fork or shovel to pull material from the outside of the pile (which is cooler and less decomposed) toward the center, and move material from the center outward. This mixes everything, brings fresh oxygen in, and keeps the pile heating up. If you don't want to turn it, leave it alone—it will decompose in 6 to 12 months without any work, just more slowly.

Recognize and fix common problems

Smell like rotten eggs or ammonia: The pile is too wet or has too many greens. Stop watering, add a thick layer of dry browns (shredded leaves or cardboard), and turn it. This should fix the smell within a few days.

Pile isn't heating up or decomposing: It's probably too small, too dry, or has too many browns. Make sure it's at least 3 feet by 3 feet, water it to sponge-like moisture, and add more greens (grass clippings or vegetable scraps). If it's still slow after two weeks, turn it to add oxygen.

Flies or fruit gnats around the pile: You likely buried food scraps too shallowly or added meat, dairy, or oils. Bury all food scraps under at least 6 inches of browns. Never add meat, fish, cheese, butter, or cooking oil—these attract pests and smell terrible. Fruit and vegetable scraps are fine.

Pile is attracting raccoons or rats: Use a bin with a tight lid, or bury all food scraps deep under browns and keep the pile moist (wet piles smell less appealing to rodents). Never add meat or dairy.

Know what you can and cannot compost

Safe to add: vegetable and fruit scraps, coffee grounds and tea bags, grass clippings, plant trimmings, fallen leaves, shredded newspaper and cardboard, straw, wood chips, and sawdust from untreated wood.

Never add: meat, fish, bones, dairy products, oils and fats, pet waste, diseased plants, weeds with seeds, or glossy or colored paper. Meat and dairy decompose slowly and smell bad. Pet waste can carry harmful pathogens. Diseased plants and seeded weeds spread problems to your garden. Glossy paper contains chemicals that don't break down.

If you're unsure about something, the safest rule is: if it came from a plant and isn't oily or diseased, it can probably go in. When in doubt, leave it out.

Harvest and use finished compost

Finished compost looks dark brown or black, crumbles easily in your hand, and smells earthy—like forest soil. It should not smell sour or have visible chunks of leaves or wood. If you see recognizable pieces, it's not ready yet; let it sit another few weeks.

If you turned the pile regularly, finished compost is ready in 2 to 3 months. If you left it alone, it takes 6 to 12 months. You don't have to wait for the whole pile to finish—you can harvest from the bottom of an open pile or bin while the top is still decomposing. Just dig out the dark, crumbly material and leave the rest to finish.

Use finished compost to enrich garden beds (mix it into the top 6 inches of soil), top-dress lawns, fill containers for houseplants, or amend potting soil. A typical pile 3 feet by 3 feet by 3 feet yields about 1 cubic yard of finished compost—enough to cover a 100-square-foot garden bed with 3 inches of compost.

Frequently Asked Questions

Can I add diseased plant material to the pile?

No. Diseases and pests can survive the composting process and spread to your garden when you use the finished compost. Throw diseased plants in the trash instead. Healthy plant trimmings are always safe.

How do I know if my pile is too wet?

Squeeze a handful of pile material. If water streams out, it's too wet. If nothing comes out, it's too dry. You want just a few drops. A wet pile smells like ammonia or rotten eggs; add dry browns and stop watering until it improves.

Can I add sawdust or wood chips?

Yes, but only from untreated wood. Sawdust and chips from pressure-treated lumber contain chemicals that don't break down and can contaminate your compost. Untreated wood sawdust and chips are safe and count as browns.

What if I don't have space for a 3-by-3-foot pile?

Smaller piles still work—they just decompose more slowly because they don't heat up as much. A 2-by-2-foot pile will take 9 to 12 months instead of 2 to 3 months. Keep the brown-to-green ratio balanced and turn it regularly if you want faster results.

Can I compost in winter?

Yes, but decomposition slows dramatically in cold weather. A pile in a warm climate or in full sun will keep working through mild winters. In freezing climates, the pile essentially pauses until spring. You can keep adding material all winter and let it all break down together when temperatures rise.