Composting on a Balcony Without the Smell
A balcony can produce real compost, and it does not have to smell or attract flies. It does require choosing the right method for a small enclosed space — an open heap is not one of them.
Why bother in a container garden
Container gardeners buy potting mix every year, which is both the largest recurring cost and the largest recurring hassle. Home-made compost and worm castings substitute for a good part of that, and worm castings in particular are an excellent, gentle soil conditioner that you cannot easily buy in small quantities.
Set expectations correctly: a balcony system will not produce enough to fill your containers. It will produce enough for top-dressing, seed-starting blends and a steady supply of liquid feed.
Three methods compared
| Method | Footprint | Smell | Speed | Takes | Effort |
|---|---|---|---|---|---|
| Bokashi bin | One 15–20 L bucket | None if sealed; tangy when opened | 2–4 weeks to ferment, then 4 weeks in soil | All food waste including cooked food, meat, dairy | Low — add daily, drain liquid |
| Worm bin | 0.3–0.5 m² stacked tray | None when balanced | 3–6 months to finished castings | Raw fruit and veg, coffee grounds, shredded paper | Medium — feed, harvest, keep moist |
| Small tumbler | 0.5–0.8 m² | Low if balanced | 6–12 weeks | Raw veg, garden waste | Medium — turn regularly, balance materials |
Bokashi: the best fit for most balconies
Bokashi is fermentation, not decomposition. Food waste goes into a sealed bucket with a bran inoculant containing effective microorganisms, and is pickled rather than rotted. Because it is anaerobic and sealed, there is no smell while the lid is on and no flies.
The process:
- Add food waste in layers, pressing down to remove air.
- Sprinkle bokashi bran over each layer — roughly a tablespoon per litre of waste.
- Keep the lid clamped shut. Drain the liquid from the tap every two or three days; diluted 1:100 it is an excellent liquid feed.
- When full, leave sealed for two weeks.
- Bury the fermented material in a pot of soil or mix it into a dedicated "soil factory" — a 40 L container of old mix — and leave four weeks. Then it is compost.
The genuine advantage: it accepts cooked food, meat and dairy, which worm bins and tumblers do not. The genuine disadvantage: you must buy bran continuously, and the output needs a second stage in soil before it is usable.
Worm bins: best for gardeners
A wormery gives you castings and worm tea, both superb for containers. Use brandling or red wigglers (Eisenia fetida), not earthworms from the garden.
- Keep it between 10 and 25 °C. Below 5 °C worms go dormant; above 30 °C they die.
- Feed little and often. Start with 250 g of worms per 1 kg of waste per week, and adjust.
- Balance with carbon: shredded cardboard, paper, egg boxes — roughly equal volume to the food.
- Keep it damp like a wrung-out sponge, not wet.
- Harvest by pushing finished castings to one side and adding fresh bedding to the other; the worms migrate over a few weeks.
Cooked food, meat, fish, dairy, oily food, citrus in quantity, onion in quantity, cat or dog waste, and diseased plants. These are what cause smells and pests. Bokashi handles all of them; worms do not.
Keeping it smell-free
Smell is almost always a symptom of one of three problems:
- Too wet. Add dry shredded cardboard or paper and improve drainage.
- Too much nitrogen. Too much food waste relative to carbon. Add browns.
- Not sealed or filtered. In a bokashi bin, replace the lid seal. In a worm bin, add a layer of damp cardboard on top and check the vent is clear.
Fruit flies are the other common complaint. Cover new food waste with a few centimetres of bedding or finished compost, freeze citrus before adding it, and hang a yellow sticky trap nearby. A healthy bin has few flies.
What to do with the output
- Worm castings: mix no more than 20–30% into potting mix, or use as a 1 cm top-dressing around established plants. Excellent in seed-starting blends.
- Worm tea / bokashi liquid: dilute to the colour of weak tea and use as a liquid feed every week or two. Apply to the mix, not the leaves.
- Finished compost: top-dress containers, blend 50:50 with fresh mix for non-fussy crops, or use as a mulch layer.
None of these are complete fertilisers. Compost improves structure and biology; you still need a feeding schedule for heavy crops.
Common questions
Does a worm bin smell?
A balanced one does not — it smells like damp soil. Smell means too much food waste, too little carbon, or poor drainage. Add shredded cardboard and check that liquid is draining freely.
How long until I have usable compost?
Bokashi produces fermented material in two to four weeks, but it needs another four weeks buried in soil. A worm bin gives harvestable castings in three to six months.
What do I do with the liquid from a bokashi bin?
Dilute it roughly 1:100 with water and use it as a liquid feed every week or two. It is nutrient-rich and acidic, so never apply it undiluted.
Is home compost as good as bought potting mix?
It is a soil conditioner, not a replacement. Use it at no more than 20 to 30% of a mix, or as a top dressing and mulch. You still need a formulated feed for heavy crops.