What Can and Can’t Go in a Backyard Compost

Every gardening book hands you a list. Greens, browns, no meat, no dairy, no glossy paper. The lists are mostly right and entirely unhelpful, because they leave out the part where you stand over the heap in the rain holding half a roast chicken and try to remember why.

This is a list with reasoning. Once you know why something is on or off it, you can make your own calls when an item is not on either.

The straightforward yeses

Anything plant-based and raw goes in. Vegetable peelings, fruit cores, salad past it, lettuce stumps, herbs that have gone leggy, the soft inner stems of broccoli. the EPA’s home-composting guide These are the heap’s bread and butter, high in nitrogen, full of moisture, breaking down fast.

Garden waste in moderation also goes in. Grass clippings, deadheaded flowers, soft prunings, weeds that have not yet set seed. Grass especially needs care; in any amount over a thin layer it mats together and turns slimy, so mix it with brown material as you add.

Used coffee grounds and tea leaves loose from the bag are excellent. They look brown but compost-wise count as green (high nitrogen). A small allotment near me composts almost half a tonne of coffee grounds a year from a local café and the heaps run hot all summer.

Shredded paper, cardboard, plain newspaper and the brown card from egg boxes are essential browns. They balance out the wet greens and keep the heap aerated. Tear card into pieces a hand’s width across or less.

Crushed eggshells go in. They will not really break down in a year, you will still see fragments, but they add calcium and they help worms.

Wood ash from untreated wood, in small amounts, goes in. A scattering, not bucketloads, and only if you are sure no painted or treated wood went into the fire.

The clear nos

Cooked food goes out of a backyard heap. Not because the food itself is the problem, anaerobic systems like bokashi handle it fine, but because cooked food smells as it breaks down in air, and the smell attracts rats. A heap that smells of last night’s pasta will have visitors within a week.

Meat, fish, bones and dairy are the same story, doubled. They will eventually decompose, but slowly, smelling along the way, attracting every fox, rat and neighbourhood cat. If you really must compost them, the answer is a sealed, hot system or bokashi pre-treatment.

Oily food and salad dressings go out. Oil coats the surface of other materials, blocks air, and slows the whole heap to a crawl.

Pet waste from cats and dogs goes out, pathogens, the wrong kind for human-edible-garden composting. Rabbit, guinea pig and hamster bedding from herbivores is fine.

Diseased plant material goes out. Tomato blight, club root, white rot on onions, these survive a normal heap and will reinfect next year’s crops. Bin them.

Weeds that have set seed or have running roots (couch grass, bindweed, ground elder) go out unless you compost hot enough to kill them, which most backyard heaps do not. The risk of spreading them around your garden is too high for the small benefit.

Glossy paper, magazines printed on coated stock, and anything with foil or plastic film go out. They do not break down properly. Plain paper and unbleached card are fine.

The grey areas

Citrus peel divides composters. It is acidic and slow to break down. In a hot, well-mixed heap it is fine in moderation. In a cold heap, large amounts of citrus can drop the pH enough to slow everything. I add the peel from a few oranges a week without thinking about it, and chop it small.

Onion and garlic skins are similar. Fine in moderation. Avoid burying whole onions that have sprouted, because they will keep growing.

Bread and pastry sit in an awkward middle. They are technically plant-based, but they attract mice and rats just as effectively as cooked food. A small slice of bread will compost; a loaf will summon trouble.

Avocado skins and stones go in, slowly. The stones will still be recognisable a year later. Some people grind them; I bury them.

Tea bags, see the longer note in the dedicated piece. The leaves are fine; many bags contain a thin layer of plastic that does not break down. Tear them open if you can be bothered; compost loose tea always.

Compostable packaging marked “home compostable” mostly composts in a hot, active heap over six to twelve months. “Industrially compostable” does not break down in a backyard at all. Treat the latter as ordinary plastic for composting purposes.

Pet hair, human hair, nail clippings, wool, yes, in small amounts, mixed in well.

Used kitchen roll, paper napkins from food, fine, unless heavily soaked in fat. The bin gets the greasy ones.

A working list to pin up

If you need a single visual rule, this works for most backyard heaps:

• If a vegetarian would eat it raw or it grew in the garden, it probably goes in.
• If it had a face, lived in a fridge, or comes out of a deep fat fryer, it probably stays out.
• If you would not be comfortable with a fox finding it on the lawn, the heap is not the place.

The half-chicken question, answered

The roast chicken in the rain belongs in the food waste caddy, not the heap. The carrot peelings from the same meal go in. The pan grease goes in the bin. The cardboard sleeve from the supermarket bird goes in shredded. The peelings of the apple pudding go in.

You will know your heap is happy when it smells faintly of forest floor when you turn it, when it heats up in spring and autumn, and when the volume keeps going down even though you are still adding to it. That last point is the magic; you can add what feels like five wheelbarrows in a month and the heap somehow stays the same size. Decomposition is a quiet kind of vanishing.

A few related guides worth your time: Apartment Composting: Three Methods That Work in Small Spaces, The Bokashi Bucket: A Beginner’s Honest Review, Worm Bins for Beginners: A Quiet Guide, and The Case for Reusable Coffee Pods (And When They Don’t Help).