How to Compost
Learn how to compost kitchen scraps and yard waste at home. Covers what to compost, the right ratio of materials, and how to maintain a bin that does not smell.
We started composting because we felt guilty about how much food we threw away. A banana peel here, coffee grounds there, vegetable scraps from cooking. It all went in the trash and eventually to a landfill where it produces methane, a greenhouse gas that is significantly more potent than carbon dioxide in the short term.
The EPA estimates that food scraps and yard waste together make up more than 30% of what we throw away. Composting diverts that waste and turns it into rich soil amendment for free.
Composting sounds more complicated than it is. You are basically piling organic material in a bin and letting microorganisms break it down into soil. The process happens with or without your help. Your job is just to create the conditions that make it happen faster and without smell.
This guide covers a basic backyard composting system. If you only have a small apartment, the same principles apply to indoor worm composting or countertop composting units.
A compost bin or a designated spot in your yard. You can buy a tumbling composter (easiest to turn), build a bin from pallets, or just pile materials in a back corner. A pitchfork or garden fork for turning the pile. A small countertop container for collecting kitchen scraps between trips to the bin. No fancy equipment is required. Composting works with nothing more than a heap of organic material on the ground.
Choose a composting method and location
For a backyard, the simplest option is an open bin or tumbler in a shady or partly shaded spot with good drainage. Place it on bare soil (not concrete) so worms and microorganisms can access the pile from below. A tumbling composter sits on a frame and rotates, which makes turning effortless but costs more. A three-sided bin made from pallets or wire mesh is cheap and effective. For apartments or small spaces, consider vermicomposting (worm composting in a small bin that fits under a sink) or a countertop electric composter that speeds up breakdown with heat. Position your bin within easy walking distance of your kitchen so you will actually use it. If it is at the far end of the yard, you will stop making trips when it rains.
Learn what goes in and what stays out
Compostable materials fall into two categories: greens (nitrogen-rich) and browns (carbon-rich). Greens include fruit and vegetable scraps, coffee grounds and filters, tea bags, fresh grass clippings, and plant trimmings. Browns include dry leaves, shredded newspaper, cardboard (torn into small pieces), straw, sawdust, and dried grass. Do not compost: meat, fish, dairy, oils (attract pests and smell terrible), pet waste (contains harmful bacteria), diseased plants (can spread disease to your garden), or anything treated with pesticides. Cooked food is borderline. Small amounts of cooked vegetables are fine. Large amounts of cooked food, especially anything oily or seasoned, can attract rodents.
Heads up: Never add meat, fish, or dairy to a home compost bin. These materials attract rats, raccoons, and flies, and they create intense odors as they decompose. Industrial composting facilities can handle these materials because they reach higher temperatures, but home bins cannot.
Layer greens and browns in the right ratio
The ideal ratio is roughly two to three parts browns to one part greens by volume. This provides the right balance of carbon and nitrogen for the microorganisms that break everything down. Too many greens and the pile becomes slimy and smelly (excess nitrogen produces ammonia). Too many browns and the pile just sits there doing nothing because there is not enough nitrogen to fuel decomposition. In practice, most people have more kitchen scraps (greens) than browns, so keep a bag of dry leaves, shredded newspaper, or cardboard near your bin. Every time you add kitchen scraps, cover them with an equal or larger volume of browns. This also prevents flies and reduces odor.
Keep the pile moist like a wrung-out sponge
Your compost pile needs moisture to support the microorganisms doing the work. The ideal moisture level is like a wrung-out sponge. If you squeeze a handful of compost material, a drop or two of water should come out. More than that is too wet. No moisture at all is too dry. In rainy climates, you may need a lid or tarp to keep the pile from becoming waterlogged. In dry climates, you may need to water it every week or two. Kitchen scraps add a lot of moisture on their own, so during wet months you may need extra browns to absorb excess water. During dry summer months, spray the pile with a hose when you turn it.
Turn the pile every one to two weeks
Turning introduces oxygen, which the decomposing organisms need to work efficiently. Without oxygen, the pile goes anaerobic (airless decomposition), which is slow and produces sulfur compounds that smell like rotten eggs. Use a garden fork or pitchfork to move material from the outside of the pile to the center, and from the center to the outside. This ensures everything gets exposed to the hot, active center of the pile where decomposition happens fastest. A tumbling composter makes this easy because you just spin it. For a bin or pile, turning takes about five minutes with a fork. You do not need to be thorough. Even a rough mixing adds enough oxygen.
Troubleshoot common problems
If your pile smells bad, it is either too wet or has too many greens. Add browns (dry leaves, shredded paper) and turn it. If it is not breaking down, it is either too dry or too many browns. Add water and some fresh greens, then turn. If you see fruit flies, bury food scraps in the center of the pile instead of leaving them on top. If you see large pests (rats, raccoons), make sure you are not adding meat or dairy, and consider a bin with a secure lid. A healthy compost pile should smell like earth or have no noticeable smell at all. If it smells like ammonia, add more browns. If it smells like sulfur, it needs more air (turn it more frequently).
Harvest finished compost
Compost is ready when it looks and smells like dark, crumbly soil. You should not be able to identify any of the original materials. The process takes two to six months depending on the size of your inputs, how often you turn, and the temperature. Hot composting (maintaining high temperatures through frequent turning and correct ratios) finishes in six to eight weeks. Cold composting (letting it sit with minimal intervention) takes four to twelve months. Harvest from the bottom of the pile where material has been decomposing longest. Screen out any large pieces that have not fully broken down and toss them back into the active pile. Use finished compost as a top dressing for garden beds, mix it into potting soil, or spread it on your lawn.
Composting is one of those things that seems complicated until you actually do it. Pile up food scraps and yard waste in roughly equal proportions. Keep it moist. Turn it occasionally. In two to six months, you have rich, dark compost that your garden plants love. Start collecting kitchen scraps in a countertop bin tonight. When it fills up, dump it into your compost bin and cover it with dry leaves or shredded paper. That is the entire routine. The finished compost you produce is better than anything you can buy in bags because it is full of diverse beneficial microorganisms specific to your local environment. It is free soil amendment that closes the loop between your kitchen, your garden, and back to your kitchen.
Questions we get asked about this
Answers from experience, not a textbook.
Not if you do it correctly. Rats are attracted to meat, dairy, cooked food, and exposed food scraps. If you only compost fruits, vegetables, coffee grounds, and yard waste, and you bury fresh scraps under a layer of browns, pests are not a significant issue. A bin with a lid and no gaps larger than a quarter inch provides extra protection. Open piles in areas with known rat problems should be enclosed in hardware cloth (wire mesh with small openings).
Yes. Decomposition slows down significantly in cold temperatures, but it does not stop entirely. The center of an established pile retains warmth even when the outside freezes. Continue adding materials throughout winter. The pile will not shrink much, but it will resume active decomposition as soon as temperatures rise in spring. Many people accumulate materials all winter and see rapid breakdown once spring arrives. You can also insulate the bin with straw bales or leaves to retain heat.
With active management (correct ratios, regular turning, proper moisture), hot composting produces finished compost in six to eight weeks. With minimal management (piling and occasional turning), cold composting takes four to twelve months. Most home composters fall somewhere in between: turning every week or two produces usable compost in two to four months during warm weather. The speed depends on the size of your inputs (smaller pieces decompose faster), temperature, moisture, and how often you turn.
Yes. Vermicomposting uses red wiggler worms in a small bin that fits under a kitchen sink or in a closet. The worms eat food scraps and produce castings (worm poop) that is excellent fertilizer. A worm bin does not smell if maintained correctly and processes about a half pound of food scraps per square foot of bin surface per week. Electric countertop composters are another option. They use heat and mechanical mixing to break down food scraps in 24 to 48 hours. They cost more but require minimal effort and no worms.
Garden Starter
How to Grow Tomatoes
How to Start a Garden
How to Compost
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