Composting turns kitchen scraps and garden waste into rich, dark soil that plants love. It costs almost nothing to start, cuts down on household rubbish, and takes only a few minutes of attention each week. A banana peel, a pile of fallen leaves, and a handful of coffee grounds might look like waste, but together they are the raw material for some of the best fertiliser a garden can get.
Many beginners put off composting because it sounds technical or messy. In practice, it is a simple natural process: tiny organisms break down organic matter, and your job is just to give them the right mix of materials, air, and moisture. This guide covers what to compost, what to leave out, how to set up a bin, and how to fix the few problems that can come up.
What Composting Actually Does
Everything organic eventually decomposes. Composting simply speeds up that process in a controlled way. Bacteria, fungi, and worms feed on the material you add, breaking it down into humus: a crumbly, earthy-smelling substance full of nutrients and beneficial microbes. Mixed into garden soil, humus improves structure, helps the soil hold water, and feeds plants slowly over time.
There is also a waste benefit. Food scraps and garden trimmings make up a large share of household rubbish. When that material goes to landfill, it breaks down without oxygen and releases methane, a potent greenhouse gas. In a compost heap, the same material breaks down with oxygen and produces carbon dioxide and water instead. A home compost bin will not solve the climate problem on its own, but it is a real, measurable reduction in what a household sends away.
Choosing a Spot and a Bin
Pick a level, well-drained spot in the garden, ideally in partial shade. Full sun can dry a heap out too fast in summer, while deep shade slows it down. Good drainage matters because a heap sitting in a puddle will turn soggy and smelly. Leave enough space around the bin to work comfortably with a fork and a wheelbarrow.
There are three common ways to compost at home. A simple open heap works if you have space and do not mind the look of it, but it is slower and can attract pests. A compost bin, either bought or built from pallets or wire mesh, keeps things tidy and holds heat better, which speeds decomposition. A tumbler is a sealed drum on a frame that you spin to mix the contents; it is the fastest option and the neatest, but it holds less material and costs more.
For most beginners, a standard bin of about one cubic metre is the best starting point. That size is large enough to heat up properly but small enough to manage. If your garden is small, a compact tumbler or a worm bin for kitchen scraps alone is a better fit. Whatever you choose, make sure the bin has air holes and sits directly on soil, so worms and microbes can move in from below.
Greens and Browns: The Mix That Matters
Everything you compost falls into one of two groups. Greens are moist, nitrogen-rich materials: fruit and vegetable scraps, coffee grounds, tea bags, fresh grass clippings, and manure from plant-eating animals. Browns are dry, carbon-rich materials: fallen leaves, straw, shredded cardboard, newspaper, twigs, and sawdust from untreated wood.
The organisms that do the work need both. Too many greens and the heap turns wet, slimy, and smelly. Too many browns and it stays dry and barely decomposes. A good working ratio is roughly one part green to two or three parts brown by volume. You do not need to measure precisely; just make a habit of covering every bucket of kitchen scraps with a generous handful of dry leaves or shredded cardboard.
Chop or shred material before adding it. Smaller pieces break down much faster because they have more surface area for microbes to work on. A kitchen knife is enough for vegetable scraps; a lawnmower run over a pile of leaves shreds them in minutes. Woody stems and branches should be cut small or put through a shredder, since thick pieces can take years to rot.
What to Compost and What to Leave Out
Safe to add: fruit and vegetable peelings, eggshells (crushed), coffee grounds and filters, tea leaves, plain cooked rice and pasta in small amounts, bread, cut flowers, grass clippings, leaves, straw, shredded newspaper and cardboard, and sawdust from untreated wood. Eggshells add calcium but break down slowly, so crush them first.
Leave out: meat, fish, bones, dairy products, cooking oil, and greasy food, which smell and attract rats. Also leave out diseased plants, weeds that have gone to seed, treated or painted wood, coal ash, and pet waste from dogs or cats, which can carry harmful organisms. Citrus peels and onion skins are fine in small amounts but can slow worms down if added in large quantities.
Building Your First Heap
Start with a layer of coarse brown material, such as twigs or straw, about fifteen centimetres deep. This creates air gaps at the base and helps drainage. Then add alternating layers of greens and browns, watering each layer lightly as you go. The heap should feel like a wrung-out sponge: damp, but not dripping.
Once the heap is built, cover it. A lid, an old piece of carpet, or a sheet of cardboard keeps in heat and moisture and keeps out heavy rain. In the first week or two, the centre of a healthy heap warms up noticeably, sometimes reaching 50 to 60 degrees Celsius. That heat is a good sign: it means the microbes are working hard, and it also kills many weed seeds and plant diseases.
Do not worry if your heap does not heat up. Small heaps, cold weather, or a mix that is too dry or too heavy on browns will all keep temperatures low. The material will still break down, just more slowly. This is sometimes called cold composting, and it works perfectly well as long as you are patient.
Turning, Watering, and Waiting
Turning the heap mixes in oxygen and moves undecomposed material from the edges into the hot centre. Turn it every two to three weeks with a garden fork, and add water if the material looks dry. A well-managed heap can produce finished compost in two to four months. A heap that is left alone may take six months to a year, and that is fine too.
The most common beginner problem is a heap that smells bad. A sour, rotten-egg smell almost always means too much green material and not enough air. Fix it by turning the heap thoroughly and mixing in dry browns such as shredded cardboard or dry leaves. A heap that smells of ammonia has too much nitrogen; again, the fix is more browns and a good turn.
If the heap is dry and nothing seems to be happening, water it and add fresh greens such as grass clippings or kitchen scraps. If it is soggy, add browns and turn it to let air in. Fruit flies around the bin usually mean food scraps are exposed on the surface; bury them under a layer of browns and the flies will disappear.
Knowing When Compost Is Ready
Finished compost is dark brown, crumbly, and smells like fresh earth. You should not be able to recognise the original materials in it, apart from the odd eggshell or twig. If the material still looks like kitchen scraps or smells sour, it needs more time.
When it is ready, the simplest test is the squeeze test: take a handful and squeeze it. Good compost holds its shape briefly and then crumbles apart. If water drips out, it is too wet and needs more browns or a few days in the open air. If it falls apart like dust, it is dry but still usable; just water it in after spreading.
Use finished compost by mixing a few centimetres into the top layer of garden beds before planting, or by spreading it as a mulch around established plants. It is also excellent for potting mixes: combine one part compost with two parts garden soil or coir. Avoid using fresh, unfinished compost directly on seedlings, since it can be too strong and may contain organisms that damage young roots.
Composting Without a Garden
People without a garden can still compost. A worm bin, kept on a balcony or even under a kitchen sink, turns vegetable scraps into rich worm castings with very little smell when managed well. Bokashi bins ferment kitchen waste, including cooked food and small amounts of meat, using special bran; the fermented material is then buried in soil or added to a compost heap to finish. Countertop electric composters dry and grind scraps into a dry powder, but they use electricity and do not produce true compost, so they are better thought of as waste reducers than soil builders.
Community composting is another option. Many towns have drop-off points or shared garden composting schemes, and some councils collect food waste separately. A quick check with the local council will show what is available nearby.
Mistakes Beginners Make
The most common mistake is adding only kitchen scraps and no browns, which creates a wet, smelly sludge. Keep a bag of shredded cardboard or dry leaves next to the bin so adding browns becomes a habit. The second mistake is adding material in large, infrequent loads rather than small, regular ones; a steady trickle keeps the microbes fed and the heap balanced.
Another mistake is putting the wrong things in. Meat and dairy in a home heap are an open invitation to rats, and diseased plants can spread problems back into the garden. When in doubt, leave it out. Finally, many beginners give up too early. A heap that looks unchanged after a month is normal in cold weather. Turn it, check the moisture, add some greens, and give it time.
Frequently Asked Questions
Does compost attract rats? A well-managed heap does not. Rats are drawn by exposed food, especially meat, bread, and cooked food left on the surface. Bury kitchen scraps under browns, keep meat and dairy out, and use a bin with a secure lid and a mesh base if rats are a known problem in your area.
Can I compost in winter? Yes. Decomposition slows in cold weather but does not stop entirely, and the heap will pick up speed again in spring. Keep adding material through winter and cover the heap to hold in what heat there is.
How much compost will I get? A full bin of raw material shrinks to roughly a third of its volume as finished compost. That is normal: much of the original weight is water and carbon that leaves as vapour and carbon dioxide.
Composting is one of those rare household habits that saves money, reduces waste, and improves the garden at the same time. Start small, keep the greens and browns balanced, and let the microbes do the work. Within a few months, the scraps from your kitchen will be feeding your soil, and the only regret most beginners have is not starting sooner.
