Every week, most households throw away a surprising amount of material that a garden would love to have: vegetable peels, coffee grounds, eggshells, fallen leaves, grass clippings. Composting turns that waste into a dark, crumbly soil amendment that improves almost any garden. It costs little or nothing, it cuts the amount of trash you send to landfill, and it gives you a steady supply of one of the best things you can add to soil.
Composting has a reputation for being complicated or smelly. It does not have to be either. At its heart, it is just organic material breaking down, which happens in nature with no help at all. A few simple habits make it faster, tidier and more reliable. This guide covers everything a beginner needs: what to put in, what to leave out, how to choose a method, and how to fix the most common problems.
How composting works
Compost is made by microorganisms, mainly bacteria and fungi, along with larger helpers such as worms, mites and beetles. They feed on organic material and break it down into simpler compounds and, eventually, humus: the stable, dark organic matter that gives good soil its color and structure.
Like any living thing, these organisms need four things: food, water, air and the right temperature. A compost pile works well when it supplies all four in balance. Most composting problems come down to one of them being out of balance, which makes them easy to diagnose once you know what to look for.
Greens and browns
The food in a compost pile comes in two broad types, usually called greens and browns. The names describe their chemistry more than their color.
Greens are rich in nitrogen. They tend to be moist and break down quickly. Too many greens and the pile becomes wet, dense and smelly.
- Fruit and vegetable scraps
- Coffee grounds and tea leaves
- Fresh grass clippings
- Fresh garden trimmings and spent plants
- Manure from plant-eating animals such as chickens, rabbits, horses and cows
Browns are rich in carbon. They tend to be dry and break down slowly. Too many browns and the pile barely breaks down at all.
- Dry leaves, ideally shredded
- Straw and dried grass
- Plain cardboard and paper, torn or shredded
- Wood chips and sawdust from untreated wood
- Dried plant stalks and pine needles
A common rule of thumb is roughly two to three parts browns to one part greens by volume. You do not need to measure precisely. Instead, watch how the pile behaves. If it smells or feels slimy, add browns. If it sits there doing nothing, add greens and water.
Keep a brown stockpile. Kitchen scraps arrive all year, but leaves arrive mostly in fall. Bag or pile dry leaves in autumn so you have browns to mix in through the rest of the year.
What not to compost
Some materials cause smells, attract pests or carry risks. In a home compost pile, leave these out:
- Meat, fish, bones and dairy. They smell as they rot and attract rats, raccoons and dogs.
- Oils and greasy food. They coat materials and slow decomposition.
- Dog and cat waste. It can carry parasites and pathogens that home piles do not reliably kill.
- Diseased plants. Many home piles do not get hot enough throughout to destroy disease organisms.
- Weeds that have gone to seed or spread by roots. Unless your pile gets very hot, you may be spreading weeds with your compost.
- Treated or painted wood, and coal or charcoal ash. They can contain chemicals you do not want in a garden.
- Glossy or coated paper and plastic-lined containers. Many “compostable” plastics need industrial facilities to break down.
Small amounts of wood ash from untreated wood can be added, but sparingly, because it is alkaline and raises soil pH.
Choosing a composting method
There is no single best way to compost. The right method depends on your space, how much material you have, and how much effort you want to put in.
Open pile or simple bin
The simplest approach is a heap in a corner of the yard, or a basic bin made from wire mesh, wooden pallets or a purchased plastic composter. Add materials as they come, mixing greens and browns. A pile about 3 feet wide, deep and tall is a good size: large enough to hold heat, small enough to turn by hand.
Many gardeners use two or three bins side by side. One is being filled, one is finishing, and one holds compost ready to use.
Tumbler
Compost tumblers are drums on a frame that you rotate to mix the contents. They are tidy, keep pests out, and make turning easy. They work best when filled in batches rather than added to continually, and they hold less material than a pile. They suit small yards and gardeners who want a contained system.
Worm composting
Worm bins, or vermicomposting, use red wiggler worms to process kitchen scraps in a container. They work indoors or in a garage, which makes them ideal for apartments and for composting through winter. The result, worm castings, is a rich, fine material that is excellent in potting mixes and as a top dressing. Worm bins need some care: keep them moist but not wet, add bedding such as shredded paper, and avoid overfeeding.
Trench and pit composting
For the least effort of all, dig a trench or hole in an empty bed, bury kitchen scraps about 8 to 12 inches deep, and cover them with soil. They break down in place over a few months. It is a simple way to enrich a bed you plan to plant later.
Hot versus cold composting
Cold composting is the relaxed approach. You add materials as they come and leave the pile largely alone. It takes longer, often six months to a year or more, but needs almost no work. Weed seeds and disease organisms may survive, so leave those out.
Hot composting is faster. You build a pile all at once with a good mix of greens and browns, keep it moist, and turn it regularly. Microbial activity can push the center of the pile to roughly 130 to 160°F, which speeds decomposition and kills many weed seeds and pathogens. A well-managed hot pile can produce finished compost in a couple of months. A compost thermometer makes it easy to track.
Most home gardeners do something in between: a mostly cold pile, turned now and then when there is time.
Building and maintaining a pile
- Pick a spot. Choose a level, well-drained area that is easy to reach from the kitchen and the garden. Partial shade keeps the pile from drying out too fast.
- Start with coarse browns. A few inches of twigs or straw at the bottom help air move into the pile.
- Layer or mix greens and browns. Each time you add kitchen scraps, cover them with a layer of browns. This reduces smells and fruit flies.
- Chop large material. Smaller pieces break down much faster. Shred leaves with a mower and cut thick stems.
- Keep it moist. The pile should feel like a wrung-out sponge: damp, but not dripping. Water it in dry weather.
- Turn it. Turning with a garden fork adds air and mixes materials. Every week or two speeds things up considerably. Every month or so is still helpful.
Troubleshooting common problems
| Problem | Likely cause | Fix |
|---|---|---|
| Rotten or sour smell | Too wet, too many greens, not enough air | Mix in dry browns and turn the pile |
| Ammonia smell | Too much nitrogen | Add browns such as leaves or shredded cardboard |
| Nothing seems to happen | Too dry, too many browns, or the pile is too small | Add greens and water, and build a larger pile |
| Fruit flies | Exposed food scraps | Bury scraps in the pile and cover with browns |
| Rodents or raccoons | Meat, dairy or oily food, or exposed scraps | Remove those foods, bury scraps, use a closed bin with a wire mesh base |
| Hot center, cold edges | Normal in many piles | Turn the pile so outer material moves to the center |
How to tell when compost is ready
Finished compost is dark brown, crumbly, and smells earthy, like a forest floor. You should not be able to recognize most of the original materials, apart from the occasional stick, eggshell fragment or avocado pit. The pile will have shrunk a lot. It is common for a pile to end up half its original volume, or less.
If the compost still feels warm, smells sour, or contains plenty of recognizable scraps, give it more time. Sifting it through a screen of half-inch hardware cloth removes lumps, which can go back into the next pile.
Unfinished compost is fine as a surface mulch, but avoid digging it into beds right before planting. As it keeps decomposing, it can temporarily tie up nitrogen and harm young seedlings.
How to use your compost
- New beds: mix about 2 inches into the top 6 to 8 inches of soil.
- Established beds: spread about an inch on the surface each year.
- Raised beds: top up beds that have settled. Our article on why raised bed soil sinks explains why this matters.
- Lawns: rake a quarter inch over the grass after core aeration.
- Containers: mix one part compost with two or three parts potting mix.
- Planting holes: mix a little into the backfill when planting perennials and shrubs.
The compost calculator works out how much you need for any bed or lawn, and the raised bed soil calculator shows how compost fits into a full bed mix.
How much compost will you make?
Less than you might hope, at least at first. Because materials shrink so much, a household’s kitchen scraps and yard waste often produce a modest amount of finished compost each year. Fall leaves make a big difference: they add bulk browns that keep the pile balanced and add to the final volume.
If you need more compost than you make, mix your own with bought or municipal compost. Many towns offer compost made from yard waste at low cost, which is a good way to cover large jobs while your own pile builds up.
Getting started this week
- Choose a method that fits your space: a bin, a tumbler or a worm bin.
- Keep a small container with a lid in the kitchen for scraps.
- Collect a stockpile of browns, such as dry leaves or shredded cardboard.
- Each time you add scraps, cover them with an equal or larger amount of browns.
- Keep the pile damp and turn it when you can.
Within a few months, you will have your first batch of homemade compost, and a garden that is noticeably happier for it.
Composting in small spaces
You do not need a large yard to compost. Apartment dwellers and gardeners with small patios have several good options.
- Worm bins fit under a sink, in a closet or on a balcony. Kept properly moist and not overfed, they do not smell, and they turn kitchen scraps into rich worm castings for houseplants and containers.
- Bokashi is a fermentation method that uses a sealed bucket and bran inoculated with beneficial microbes. It can handle some foods that regular piles cannot, such as small amounts of cooked food. Bokashi does not produce finished compost on its own. The fermented material is then buried in soil or added to a compost pile to finish breaking down.
- Compact tumblers fit on a patio and keep everything contained.
- Community composting programs, drop-off sites and curbside food scrap collection are increasingly available in US cities. Check with your city or county.
Do you need to buy a compost bin?
No. A simple heap works perfectly well, and many experienced composters never use anything more. A bin does help keep things tidy, holds heat and moisture better than an open heap in some climates, and discourages animals. A homemade bin from wooden pallets or a cylinder of wire mesh costs little and works as well as many purchased models. If you buy one, look for a design that is easy to load, has good air flow, and lets you get finished compost out of the bottom or side without emptying the whole thing.
Frequently asked questions
How long does compost take?
A well-managed hot pile that is turned regularly can be ready in about two to three months. A cold pile that is mostly left alone usually takes six months to a year or more.
What is the right ratio of greens to browns?
Roughly two to three parts browns to one part greens by volume is a good starting point. Adjust based on how the pile behaves: add browns if it smells, and add greens and water if it is not breaking down.
Can I compost in winter?
Yes. Decomposition slows down in cold weather, but you can keep adding scraps. The pile will break down faster once it warms up in spring. Worm bins kept indoors work year-round.
Does compost smell bad?
A healthy compost pile smells earthy. A bad smell usually means it is too wet or has too many greens. Mix in dry browns and turn it to add air.
Can I compost citrus peels and onions?
Yes, in a regular compost pile, in moderation. Worm bins are more sensitive, so add citrus and onions sparingly or not at all there.
Do I need to turn my compost?
No, but turning speeds it up by adding air and mixing materials. An unturned pile still becomes compost, just more slowly.