Why a small flat is no barrier to composting

If you live in a flat, the idea of keeping a compost bin indoors might conjure images of fruit flies, slime, and a smell that lingers in the hallway. But here’s the truth: a well-managed indoor compost system is tidy, compact, and surprisingly odour-free. The secret isn’t magic – it’s understanding that smells come from anaerobic conditions, where scraps rot without air. Give your composting microbes the right environment, and they’ll work quietly and efficiently, turning your tea bags and carrot peelings into dark, crumbly gold. You don’t need a garden, just a little counter space and a simple routine.

Pick a system that suits your space

The first step is choosing a method that fits your kitchen and your lifestyle. Most indoor composters fall into three broad camps, and each has its own quirks.

• Bokashi bin: A sealed bucket that ferments everything – including cooked food, meat, fish, and dairy – using a bran inoculated with beneficial microbes. It produces a liquid feed that you drain every few days. The fermentation process smells vaguely pickled, not rotten, and the bin can sit under the sink.
• Wormery: A stack of trays home to hundreds of composting worms. They eat fruit and vegetable scraps, tea leaves, and coffee grounds, producing rich castings and a liquid feed. Wormeries need a cool spot, consistent moisture, and a little patience, but they are brilliant for small spaces.
• Sealed bucket or tumbler: A simple lidded container – ideally with a tap at the bottom – that you fill with alternating layers of kitchen scraps and shredded cardboard. Turn it regularly to aerate. This works best if you have a balcony or a shed, but a small, well-managed bucket can live indoors too.

Master the greens and browns balance

Every compost pile, whether it’s a bokashi bin or a wormery, relies on a balance between “greens” and “browns”. Greens are nitrogen-rich and wet: vegetable peelings, fruit cores, tea bags, coffee grounds, and fresh grass clippings. Browns are carbon-rich and dry: shredded cardboard, egg boxes, newspaper, toilet roll tubes, dry leaves, and sawdust.

The golden rule indoors is to aim for two to three parts browns to one part greens by volume. Too many greens, and you get a soggy, smelly mess. Too many browns, and decomposition slows to a crawl. Every time you add a handful of kitchen scraps, cover it with a generous handful of shredded cardboard or torn newspaper. This simple habit keeps the surface dry, traps any potential odours, and stops fruit flies from laying eggs.

Chop things small, too. A banana skin cut into strips breaks down far faster than one left whole, and smaller pieces mean less chance of anaerobic pockets forming.

Daily routines that keep things sweet

Consistency is everything. A few small habits will keep your indoor bin fresh and productive.

• Use a freezer caddy: Keep a small lidded container in the freezer for scraps. Freezing breaks down cell walls, speeds up composting later, and stops the scraps from decomposing – and smelling – before you add them to the main bin.
• Layer as you go: Never dump a pile of scraps and leave them exposed. Add, then cover with browns. Every single time.
• Stir or shake: Give your bin a gentle turn or shake every few days to introduce air. For a wormery, use a small fork to gently fluff the bedding without disturbing the worms too much.
• Drain the liquid: Bokashi bins and wormeries both produce a nutrient-rich liquid. Drain it every two to three days – if left, it can become smelly and stagnant. Dilute it 1:10 with water for your houseplants and balcony pots.
• Check moisture: Squeeze a handful of the contents. It should feel like a wrung-out sponge – moist but not dripping. If it’s too wet, add more shredded cardboard. If it’s too dry, mist with a little water.

Troubleshooting: if it starts to smell

Even the best composters have off days. A whiff of rotten eggs or ammonia means something is out of balance. The fix is almost always the same: add more browns. Tear up a few cardboard boxes or newspaper, mix them through, and the smell should subside within a day.

Other culprits include overfeeding a wormery – give the worms a week to catch up – or adding too many citrus peels, which can make the bin acidic. For a bokashi bin, a sour, pickled smell is normal; a truly foul, bin-like odour means it’s too wet or you haven’t added enough bran. Sprinkle in an extra handful and drain the liquid.

If fruit flies appear, you’ve left greens exposed. Bury them deeper or wrap them in newspaper before adding. A tight-fitting lid and a layer of dry browns on top are your best defences.

Using your compost in small spaces

Once your bokashi bin is full, you have a bucket of fermented pre-compost. It needs to finish breaking down – either buried in a friend’s garden, added to a second sealed bin with more browns, or mixed into a balcony planter and left for a few weeks. Worm castings are ready when the tray is dark, crumbly, and free of recognisable scraps. Use them as a top dressing for houseplants, mix them into potting compost, or make a nutrient-rich tea by steeping a handful in water for a day.

Nothing beats the quiet satisfaction of watching a bag of carrot tops and coffee grounds transform into something your plants adore. Start small, keep your browns handy, and you’ll soon wonder why you ever threw those scraps away.