Most guides on how to start composting make it sound like a chemistry exam. It is not. A pile of dead plant material will rot whether or not you do anything, and everything below is just about making it rot faster, without smelling. There are only four variables to get right: carbon, nitrogen, air, and water. Get those roughly balanced and you have free soil improver in a few months.
Quick answer: To start composting, pick a level, well drained spot and build a pile at least 3 feet by 3 feet by 3 feet, mixing roughly 3 parts brown material such as dry leaves and cardboard with 1 part green material such as food scraps and grass clippings. Keep it as damp as a wrung out rag, turn it every 1 to 2 weeks to add air, and it will heat to 140 degrees and be finished in 2 to 6 months. Never add meat, bones, dairy, oils, diseased plants, or pet waste.
Key takeaways
- Aim for a carbon to nitrogen ratio around 25 to 30 to 1, which in practice is roughly 3 parts browns to 1 part greens by volume.
- Size matters more than people think. Under 3 cubic feet a pile cannot hold heat; over 5 cubic feet air cannot reach the middle.
- Damp rag, not wet sponge. Moisture is the most common thing people get wrong after the brown to green ratio.
- Smell is a diagnosis. Ammonia means too much green. Rotten egg means no air. A working pile smells earthy.
- No meat, bones, dairy, oil, diseased plants, aggressive weeds, or pet waste. These bring pests, pathogens, and odour.
- Turning is optional but it is the speed dial. Turned piles finish in 2 to 3 months, ignored piles in 6 to 12.
What is compost, and what is actually happening?
Compost is what is left when microbes have eaten everything easily edible in a pile of dead plant material. Those microbes are already present on the leaves and scraps you throw in. You are not making compost so much as running a feeding station for bacteria and fungi, and the four things they need are carbon for energy, nitrogen for protein, oxygen to breathe, and water to live in.
When the balance is right, the microbes multiply so fast that the pile heats itself. Penn State Extension puts the target at a carbon to nitrogen ratio of 25 to 30 parts carbon to 1 part nitrogen, with the pile reaching 140 to 160 degrees Fahrenheit, hot enough that the surface feels hot to the touch. That heat is the point: it is what kills weed seeds and pathogens, and it is the difference between compost and a cold heap of half rotted vegetable peel.
Browns and greens: the only ratio you need
Forget the number 30 to 1 for a moment. In a garden, the working rule is about 3 parts brown to 1 part green by volume. Browns are dry, dead, and carbon rich. Greens are fresh, wet, and nitrogen rich. Green does not mean the colour: coffee grounds are brown and count as a green.
| Browns (carbon) | Greens (nitrogen) | Never add |
|---|---|---|
| Dry fallen leaves | Vegetable and fruit scraps | Meat and fish |
| Cardboard and paper, shredded | Grass clippings | Bones |
| Straw | Coffee grounds and filters | Dairy and cheese |
| Wood chips and sawdust | Tea leaves | Oils and fat |
| Pine needles | Fresh plant trimmings | Diseased plants |
| Egg cartons | Crushed eggshells | Aggressive weeds and seed heads |
| Twigs, chopped small | Spent flowers | Dog and cat waste |
The rules in that third column are not fussiness. Meat, bones, and dairy attract rats and produce genuinely foul smells. Oils coat material and block the air microbes need. Diseased plants can survive a pile that never gets properly hot, and you would be spreading the problem back onto your garden. Pet waste from carnivores carries pathogens that home composting does not reliably kill.
If you want to compost kitchen scraps without walking outside every evening, a countertop bin with a carbon filter is the practical answer, and the best kitchen compost bins hold about a week’s scraps without any smell reaching the room. For the pile itself, the best compost materials guide covers what is worth adding and what is filler.
Which composting setup should you use?
- Open heap. Free, unlimited size, slowest to look tidy. Fine at the back of a large garden.
- Enclosed bin. The default for most homes. It keeps heat and moisture in, looks acceptable, and deters casual pests. The best compost bins come in sizes that actually hit that 3 cubic foot minimum, which cheap ones often do not.
- Tumbler. Turning is easy, so it is fast, but capacity is small and most tumblers are too small to hold real heat.
- Wire or pallet bin. Cheap, big, and airy. Dries out fast in summer.
Whatever you choose, put it on bare soil rather than concrete if you can, in a spot with some shade so it does not bake dry, and where you can reach it with a hose and a wheelbarrow.
How do you start composting step by step?
- Choose the spot. Level, well drained, part shade, on soil so worms and microbes can move in from below. Not against a wooden fence you care about.
- Build it big enough. At least 3 feet in each direction, and no more than 5. Smaller cannot hold heat and larger suffocates in the middle.
- Start with a coarse brown layer. Twigs or coarse stems at the bottom, 4 to 6 inches, to let air in underneath and drainage out.
- Layer 3 parts brown to 1 part green. Alternate layers a few inches thick rather than dumping a bucket of grass clippings in one lump, which mats into a slimy anaerobic layer.
- Chop things smaller. Smaller pieces mean more surface area for microbes. Running the mower over leaves is the easiest way to do this at scale.
- Water to damp rag. Squeeze a handful: it should feel like a wrung out cloth and release a drop or two, not a trickle.
- Cap with browns. Always finish with a brown layer on top. It stops flies and holds smell in.
- Wait a week, then check the heat. Push your hand in, or use a compost thermometer. A working pile is hot in the middle within a few days.
- Turn every 1 to 2 weeks. Move the outside to the middle. Each turn re oxygenates the pile and restarts the heating cycle.
- Harvest when it is dark, crumbly, and smells of earth. Nothing recognisable should remain. Expect 2 to 3 months if you turn it regularly, 6 to 12 if you do not.
Turning is the single biggest lever on speed, and a garden fork does it better than a shovel because it lifts and separates rather than slicing. If turning is the part you dread, our guide to composting with a garden fork covers the technique that makes it less work.
Troubleshooting: your pile is telling you something
| Symptom | Cause | Fix |
|---|---|---|
| Smells like ammonia | Too much green, excess nitrogen escaping as gas | Mix in browns: leaves, shredded cardboard |
| Smells rotten or sour | Too wet and airless, gone anaerobic | Turn it, add dry browns, improve drainage |
| Nothing is happening, pile stays cold | Too small, too dry, or too many browns | Add greens and water, or build it bigger |
| Dry and dusty | Not enough water | Water while turning, cap with browns |
| Flies and pests | Exposed food scraps | Bury scraps in the middle, cap with browns |
| Slimy grass layer | Clippings dumped in one thick lump | Break it up and mix through browns |
Grass clippings are worth a note of their own. They are an excellent green, but a bucket of them in one layer mats into an airless slab that goes sour. Mix them through browns, and remember you do not need to bag them at all: as covered in how to mow a lawn, leaving clippings on the lawn returns roughly one fertilizer application a year to the grass for free.
How do you use finished compost?
Finished compost is a soil improver, not a fertilizer. Its nutrient content is real but low and slow, and its main value is structure: it helps sandy soil hold water and clay soil drain and breathe. Do not plant directly into pure compost.
- Beds and borders: spread 1 to 2 inches and fork it into the top few inches, or just lay it on top and let the worms do it.
- Lawns: topdress a thin layer, no more than 1/4 inch, ideally straight after aerating. See how to aerate a lawn for why that timing works.
- Vegetable beds: mix it into the existing soil rather than filling a bed with it. If you need bulk to fill a new raised bed, the best compost to buy for vegetable gardens is a faster answer than waiting on your own pile.
- Do not expect it to feed a hungry lawn. Compost improves soil; nitrogen still comes from the rates covered in how to fertilize a lawn.
Frequently asked questions
What is the ratio of browns to greens in compost?
Roughly 3 parts brown to 1 part green by volume, which gives the carbon to nitrogen ratio of about 25 to 30 to 1 that microbes work best at. Too much green releases nitrogen as ammonia and smells. Too much brown starves the microbes and the pile barely decomposes.
How long does compost take?
Two to three months if you build a pile of at least 3 cubic feet, keep it damp, and turn it every 1 to 2 weeks. Six to twelve months if you simply add material and ignore it. Turning is the main speed control, because it re oxygenates the pile and restarts the heating cycle.
Why does my compost smell bad?
Ammonia means too much nitrogen, so mix in browns like dry leaves or shredded cardboard. A rotten, sour smell means the pile is too wet and has gone anaerobic, so turn it and add dry material. A healthy pile smells earthy, like a forest floor, and never offensive.
Can you compost meat and dairy?
No. Meat, fish, bones, dairy, and oils attract rats and other pests, create severe odours, and coat material so air cannot reach the microbes. Home piles rarely stay hot enough for long enough to break them down safely. Stick to plant material, coffee grounds, and eggshells.
Do you need to turn compost?
Not strictly. An untouched pile still becomes compost, it just takes 6 to 12 months instead of 2 to 3 and never gets hot enough to kill weed seeds. Turning every 1 to 2 weeks adds oxygen, which is what lets the pile heat to 140 degrees and work fast.
How wet should a compost pile be?
Like a wrung out rag. Squeeze a handful and it should feel damp and release maybe a drop, not a trickle. Too dry and the microbes go dormant and the pile stalls. Too wet and it goes airless and starts to smell sour. Water while turning to mix it evenly.
Final thoughts
Starting compost is easier than the internet suggests. Build it at least 3 feet cubed, feed it roughly 3 parts brown to 1 part green, keep it as damp as a wrung out rag, and turn it when you remember. If it smells, the pile is telling you which of those four you got wrong, and the fix is always a handful of leaves or a turn with a fork. If you want it contained and tidy from day one, start with the best compost bins and size up rather than down.