Composting for beginners

Composting turns kitchen scraps and garden waste into dark, crumbly material that feeds soil and helps it hold water. It also keeps a surprising amount of rubbish out of your bin: food and garden waste can make up a large share of what a household throws away. You don’t need a big garden or special equipment to start. You need the right mix of ingredients, some air, and a little patience.

How composting works

Bacteria, fungi, worms and insects break down organic material. To do that efficiently they need four things: nitrogen (from “greens”), carbon (from “browns”), oxygen and moisture. When the balance is right, a pile warms up as microbes get to work. When it is wrong, the pile either smells or does nothing at all.

Greens (nitrogen)	Browns (carbon)	Keep out of a home bin
Fruit and vegetable scraps	Dry leaves	Meat, fish and bones
Coffee grounds and filters	Shredded plain cardboard and egg boxes	Dairy products
Tea leaves (plastic-free bags)	Straw and hay	Oily or greasy food
Fresh grass clippings	Small twigs and wood chips	Dog and cat waste
Plant trimmings	Paper towels and plain paper	Diseased plants and weeds with seeds

A good starting mix is roughly three parts browns to one part greens by volume. In practice, every time you empty a small kitchen caddy, add two or three handfuls of shredded cardboard or dry leaves on top.

Choosing a compost system

• Open heap: free, needs space, best for large gardens.
• Plastic bin with a lid: tidy, keeps rain and pests out; many councils sell them cheaply.
• Tumbler: easy to turn and faster, but more expensive and needs enough material to work well.
• Wormery: works on a balcony; worms process kitchen scraps into rich worm castings.

Setting up your first bin, step by step

1. Place the bin on bare soil in a partly shaded spot, so worms and microbes can move in from below.
2. Start with a 10–15 cm layer of twigs or straw for airflow at the bottom.
3. Add greens and browns in thin alternating layers, chopping large scraps into smaller pieces.
4. Keep the mix as damp as a wrung-out sponge. Add water in dry spells, more browns if it gets soggy.
5. Turn or stir the pile every one to two weeks with a garden fork to let air in.

Troubleshooting

Problem	Likely cause	Fix
Rotten or ammonia smell	Too wet, too many greens, not enough air	Mix in browns and turn the pile
Nothing seems to happen	Too dry or too many browns	Add greens and a little water
Fruit flies around the bin	Scraps left exposed on top	Always cover new scraps with browns
Rats or mice	Cooked food or bread in the bin	Keep to raw scraps; use a closed bin on a mesh base
Slimy, flattened grass	Thick layers of fresh clippings	Add clippings in thin layers mixed with browns

When is compost ready?

Finished compost is dark brown, crumbly and smells like a forest floor. You shouldn’t be able to recognise the original scraps, apart from the odd eggshell. A well-managed, regularly turned pile can be ready in two to three months; a cold heap that is left alone may take a year. Many gardeners run two bins: one being filled and one quietly finishing.

How to use it

• Spread a 3–5 cm layer on vegetable beds in spring; see how to start a vegetable garden.
• Mix a little into potting compost for containers.
• Use it as a mulch around shrubs and trees to keep moisture in.

Sieve out any large pieces and throw them back in the bin to keep breaking down. Nothing is wasted.