How to Compost in a Flat: Three Methods for Small Spaces

Composting in a flat means choosing a method that doesn't need a garden: a bokashi bin, an indoor wormery, or your council's food waste collection all work within a few square feet of cupboard or balcony. None of them smell if you run them properly, and none need outdoor space. Ecomojo has covered food waste from several angles, and this one is about doing something with it when you have nowhere to dig a heap.

The honest starting point is that flat composting is a different activity from garden composting. You're not trying to build a heap that breaks down slowly over months. You're trying to get food scraps out of your bin before they rot into something unpleasant, using a method sized for where you actually live.

Why composting in a flat is different from composting in a garden

A garden compost heap relies on volume, airflow and worms arriving on their own, none of which a flat can offer. Indoor methods replace that with a sealed or controlled system: a bucket with a tight lid, a worm bin with ventilation holes, or a caddy destined for someone else's collection point. The trade-off is that you manage the process more closely, in exchange for it fitting under a sink.

This matters because the usual advice about turning a heap or leaving it to nature doesn't apply here. Every flat-friendly method asks you to do something active: drain a bin, feed worms a measured diet, or simply remember collection day. Picking the method that matches your patience and your kitchen is more useful than picking the one that sounds most impressive.

Bokashi composting for small kitchens

Bokashi is a fermentation method, not decomposition in the usual sense: you layer food scraps in a sealed bucket with a bran inoculated with microbes, and the microbes pickle the waste rather than rotting it. Because the bucket stays sealed, it doesn't attract flies and barely smells beyond a faint sour-sweet note. It also accepts things garden compost struggles with, including small amounts of cooked food, meat trimmings and dairy.

What you need and how it runs

A bokashi kit is two stacking buckets with a tap at the base, plus a bag of the bran. You add scraps, sprinkle bran over the layer, press it down to push out air, and seal the lid. The tap lets you drain off a liquid by-product, which diluted makes a plant feed; undiluted, it's strong enough to use as a drain cleaner.

Where the fermented waste goes next

Once a bucket is full, the contents need to finish breaking down somewhere, because fermented scraps aren't ready to use directly. Some flats have access to a communal garden bed or a neighbour with a planter who will take a bucket of pre-treated waste. Where that isn't available, some councils accept bokashi waste in food waste collections, so it is worth checking before buying a kit.

Keeping a wormery indoors

A wormery is a stack of ventilated trays where composting worms eat through food scraps and shredded paper, leaving behind a dark, crumbly compost and a liquid feed. Unlike bokashi, it's true decomposition, so it only takes plant-based scraps: no meat, no dairy, no large amounts of citrus or onion, which worms avoid. Done properly, a wormery kept somewhere with stable temperature and some airflow doesn't smell like rubbish; it smells faintly earthy, closer to a plant pot than a bin.

• Fruit and vegetable peelings, cut small so worms can process them faster
• Tea leaves and coffee grounds, including the paper filter or bag if it's plastic-free
• Shredded cardboard or newspaper, used as bedding and to balance wet scraps
• Crushed eggshell, in small amounts, for grit

A wormery needs a spot that doesn't freeze in winter or bake in summer sun, which rules out most balconies in extreme weather but suits a utility cupboard, a hallway or a shaded spot indoors. If you're deciding what else belongs in the bin before it reaches the worms, the full breakdown of what you can compost at home is worth reading alongside this.

Food waste collection as the low-effort option

Where bokashi and wormeries ask for ongoing attention, a kitchen caddy linked to your council's food waste collection asks for almost none: scraps go in a lined caddy, the caddy goes out on collection day, and the processing happens elsewhere. Not every area runs this service yet, though coverage across the UK has been expanding, so it's worth checking your council's waste pages before ruling it out. If the service exists where you live, it accepts a wider range of waste than either composting method, including cooked food, bones and food past its best.

The compromise is that you lose the finished compost yourself; it goes into a shared industrial process rather than back into your own plant pots. For a flat with no plants and no interest in managing a bin, that compromise is often the right one.

Dealing with smell and fruit flies in a small space

Smell and fruit flies are the two worries that stop people starting, and both come down to the same cause: scraps sitting exposed to air for too long. A sealed bokashi bucket avoids this by design, and a wormery avoids it by burying fresh scraps under existing bedding rather than leaving them on top. A loose kitchen caddy is the method most likely to cause problems, simply because the lid gets left open more often.

Fruit flies arrive to lay eggs on exposed, ripening scraps, not on a bin that's properly sealed, which is why the lid matters more than the bin itself.

A thin layer of shredded paper or a tight-fitting lid solves most of this. Freezing particularly smell-prone scraps, like fish trimmings, until collection or transfer day also helps, and pairs well with the ideas in the piece on storing food without plastic, since the same containers often do double duty.

Choosing between the three methods

None of these methods is wrong for a flat; they simply suit different routines. Someone who already keeps houseplants and wants free compost gets more from a wormery or bokashi bucket. Someone who wants food waste handled with minimum thought is better served by a collection scheme, where one exists.

Starting this week

1. Check your council's website for a food waste collection service and whether it accepts bokashi residue.
2. Measure the space you have free, such as under the sink or in a utility cupboard, before choosing a method.
3. If choosing bokashi, buy a starter kit with enough bran to cover the first few weeks.
4. If choosing a wormery, source composting worms separately, since kits rarely include them.
5. Line a small caddy with newspaper or a compostable liner to collect scraps before they go into whichever system you've chosen.
6. Keep a lid nearby at all times and get into the habit of closing it straight after use.

Once a method is running, the habit that keeps it going is smaller than people expect: a lidded container on the counter, scraps going in through the day, and a short walk to the bin, the wormery or the balcony each evening. If you're building wider kitchen habits around this, the guide to a zero waste kitchen covers swaps that work alongside any of these composting methods, and the piece on what a circular economy actually means explains why keeping food waste out of landfill matters beyond your own kitchen.

#Composting #Food waste #Kitchen swaps

Download PDF: Flat composting setup checklist PDF, 28 KB