Why bother making compost?

Roughly a third of the average UK household bin is food waste, and a good chunk of what goes into the garden waste sack could be recycled on site too. Composting at home turns that problem into a free, steady supply of the best soil improver you can get your hands on. Nothing you buy in a bag is quite as good as the crumbly, sweet-smelling stuff that comes out of your own heap, and if you're gardening peat-free, home-made compost is the perfect partner to a peat-free potting mix.

It's also one of the simplest wildlife-friendly habits you can adopt. Healthy compost is alive with fungi, bacteria, worms and beetles, and a well-built heap becomes a warm winter refuge for hedgehogs, slow worms and toads. Feed the soil and you feed everything above it.

Getting the greens and browns balance right

Every compost heap is a simple equation. You need carbon-rich browns for structure and energy, and nitrogen-rich greens for the microbes that do the work. Aim for roughly two to three parts browns to one part greens by volume. Too many greens and the heap turns into a slimy, smelly mess; too many browns and it sits there for years doing very little.

• Greens: vegetable and fruit peelings, tea leaves and plastic-free tea bags, coffee grounds, grass clippings, annual weeds before they seed, dead-headed flowers, nettles and comfrey leaves.
• Browns: shredded cardboard and plain paper, loo roll tubes, egg boxes, straw, autumn leaves, woodchip, hedge trimmings, sawdust from untreated timber, and spent bedding from vegetarian pets.

Grass clippings are the classic beginner's trap. In May and June, mowings arrive faster than the heap can cope with, so mix each batch with shredded cardboard or add them in thin layers. Better still, leave the clippings on the lawn — it feeds the grass and saves you the job.

What to add, and what to leave out

Be generous but be sensible. Anything that once grew can go in, with a few exceptions. Avoid perennial weed roots such as bindweed, ground elder and couch grass unless your heap reliably heats up, and keep out diseased material like clubroot-infected brassicas or blight-ridden tomato haulms. These belong in the council green waste collection, where commercial temperatures kill the problem.

Kitchen-wise, raw fruit and veg trimmings are ideal. Cooked food, meat, fish, dairy and oily leftovers attract rats and foxes, so if you want to compost them you'll need a sealed bokashi-style system or a rodent-proof hot bin. Leave out cat litter, dog faeces, disposable nappies, coal ash and glossy magazines.

A wormery is a lovely solution for a small garden or a flat with a balcony. Worms munch through kitchen scraps happily, and the liquid they produce, diluted to roughly one part to ten with water, makes a superb tomato feed.

Siting and building your heap

Site your bin or bay on bare soil in a spot that gets some sun, not in deep shade where it will stay cold and wet. A heap of about one cubic metre is the sweet spot — big enough to hold heat, small enough to turn. Two bays side by side make turning easy: fill one, turn it into the other, then start again.

If you're using a plastic dalek bin, add a layer of twiggy prunings at the base for drainage and airflow. For a pallet bay, line the sides with cardboard to keep the warmth in. Start with a 15cm layer of coarse browns, then alternate greens and browns in thin layers, sprinkling a little soil or old compost between them to introduce the microbes that get things going.

Keeping the heap cooking

Two things matter most: moisture and air. Squeeze a handful of the contents — it should feel like a wrung-out sponge. If it's drier than that, water it as you turn; if it's soggy and whiffy, fork in more cardboard and give it a good mix.

Turning is what separates a slow, cold heap from a fast, hot one. A well-managed pile can reach 60–70°C within a week, hot enough to steam on a frosty morning and to kill many weed seeds and pathogens. Turn it every two to four weeks to bring the outside to the middle, and you could have finished compost in as little as eight weeks through summer. Leave it unturned and you'll still get good compost — it will just take six to twelve months.

Winter slows everything down, and that's fine. Insulate the top with a layer of cardboard or an old carpet and let it tick over quietly until spring warms it up again.

Knowing when it's ready, and how to use it

Finished compost is dark, crumbly and smells of woodland floor rather than rot. You shouldn't be able to recognise much of what went in, apart from the odd eggshell or woody stem. If it's still chunky, sieve it: return the lumps to the next heap and use the fine stuff.

Spread it as a mulch around perennials and shrubs, dig it into veg beds, mix it with leafmould and grit for potting, or steep a couple of handfuls in a bucket of water for a week to make a gentle liquid feed. However you use it, you're closing the loop — less in the bin, more life in the soil, and a garden that gets a little richer every year.