A Simple Guide to Composting Kitchen Waste

Why a compost heap earns its place

Every kitchen in the country throws out something a compost heap would happily eat: peelings, apple cores, tea leaves, coffee grounds, the tired outer leaves of a cabbage. Add them to a bin and leave the microbes to it, and within a few months you have dark, crumbly, sweet-smelling compost — the single most useful thing you can put on a vegetable bed or around a fruit bush. It feeds the soil rather than just the plant, holds moisture through a dry July, and saves a fortune in bagged compost. For anyone keeping a few hens, a potager or a half-acre, it is the cheapest soil improvement going.

You do not need a fancy tumbler or an allotment-sized setup. A dalek bin in a corner, or three pallets wired into a square, will do the job beautifully.

Greens and browns: the balance that makes it work

Composting is not really rotting, it is farming. You are feeding bacteria, fungi and worms, and they have a diet like any other livestock. It comes down to two ingredients, and the relationship between them.

Greens are wet and rich in nitrogen: vegetable and fruit peelings, tea leaves, coffee grounds, grass clippings, fresh plant trimmings, annual weeds pulled before they set seed.

Browns are dry and rich in carbon: torn cardboard and egg boxes, newspaper, straw, wood shavings, dead leaves, dried hedge clippings, the cardboard middles of toilet rolls.

Aim for roughly two or three parts browns to one part greens, by volume. Too many greens and the heap goes slimy, smells of ammonia and hums with flies. Too many browns and it sits there dry and motionless for a year. When in doubt, add browns, and tear or shred them small so they break down quickly.

• Squeeze test: a handful should feel like a wrung-out sponge — damp, not dripping.
• Chop the chunky stuff: sprout stalks, citrus skins and corn cobs take an age unless cut up.
• Layer it: alternate a green layer with a brown one rather than tipping everything in at once.

What to put in, and what to leave out

Almost all uncooked kitchen waste belongs on the heap. Cooked food is the exception: it draws rats, foxes and badgers, and in a small garden it is better dealt with in a sealed bokashi bin or a wormery. If you keep a wormery, cooked scraps, dairy and even small amounts of meat can go in, but never into an open heap.

Keep out the following, whatever the temptation:

• Meat, fish, bones, dairy and oily food — the classic rat magnet.
• Dog and cat faeces, and used cat litter.
• Perennial weed roots such as bindweed, ground elder and couch grass, unless your heap runs genuinely hot.
• Diseased plant material — potato blight, clubroot, rose blackspot.
• Glossy magazines, plastic-coated receipts and anything shiny.
• Tea bags with a plastic mesh, unless you are happy to pick them out later.

Citrus peel and onion skins are fine in moderation; in bulk they slow things down, so mix them through rather than dumping a whole bag in one spot.

Siting and building the heap

Put the bin somewhere you will actually walk to in the rain, ideally on bare soil or paving with a few inches of coarse twigs at the base so excess water drains and worms can climb in. Sun is a bonus: a heap in full sun stays warmer and works faster. Make sure the lid fits and can be weighted down, because a bin that blows open in a gale is an invitation to every scavenger in the parish.

Keep a small lidded caddy by the kitchen door and empty it every two or three days. Add a layer of browns each time — a handful of torn cardboard or a scoop of leaves stops the caddy going sour and keeps the heap in balance from the start.

Turning, moisture and heat

A well-made heap heats up on its own. Within a few days the middle should feel warm to the hand, and a proper hot heap will reach 55–65°C, enough to kill many weed seeds and pathogens. That heat is your feedback: if it never warms, something is out of balance.

Turn the heap every two to four weeks with a fork, bringing the outside to the middle and the middle to the outside. It is not strictly necessary, but it speeds everything up considerably and lets you check the moisture as you go. Water it with a can if it has dried out, and fork in more browns if it is soggy. In winter, everything slows; a cold snap does not mean failure, just patience.

When it is ready, and how to use it

Depending on method and season, you will have compost in anything from three months to a year. It is ready when it looks like coarse, dark crumbs, smells of woodland floor rather than rot, and you cannot recognise the original ingredients. If there are still eggshells and twiggy bits, sift it through a frame of chicken wire and return the leftovers to the next heap as starter material.

Use it as a mulch around hungry crops, fork it into the top few inches of a bed, or mix it with sieved loam and grit for a decent potting blend. A dressing of your own compost each spring does more for a vegetable plot than anything you can buy in a bag — and it began life as a bucket of peelings by the back door.