Bokashi Composting: Fermenting Food Waste in a Flat or Small Garden

Bokashi is pickling, not composting: food scraps layeredPropagating a new plant by pinning a low, flexible stem into the soil while still attached to the parent, so it roots before being cut free. Full definition → with inoculated bran in a sealed bucket ferment instead of rotting, so a bucket under the sink can take cooked food, meat, dairy and citrus that an ordinary compost bin can't. It makes pickled waste, not finished compost, so you need somewhere to bury it or add it to a heap afterwards. Add a layer of scraps, sprinkle over a handful of bran laced with lactic acid bacteria and yeasts, press the air out and clip the lid down. The same microbial family that turns cabbage into sauerkraut and milk into yoghurt goes to work on the waste, souring it in an oxygen-free bucket rather than breaking it down the way a heap does.

What bokashi is

Bokashi is an anaerobic fermentation method, not composting in the usual sense. It is done in a small airtight bucket, usually one of a matching pair, each with a drainage tap. Scraps go in layered with "bokashi bran", a carrier such as wheat, rice husk or sawdust inoculated with effective microorganisms, mainly lactic acid bacteria and yeasts. Sealed from air, they ferment the waste rather than rot it, which is why bokashi tolerates cooked food, meat, dairy and citrus that would cause problems in a cold heap or a wormery. Fermentation preserves the waste and arrests the smelly decay you get from food left in a bin bag, but it doesn't turn it into compost by itself.

Step by step

1. Layer. Add scraps cut into smaller pieces so more surface touches the bran, and sprinkle a handful of bran over roughly every inch (about 3cm) of waste; Garden Organic suggests about a tablespoon per layer, so follow your kit's instructions. Break up large bones or leave them out. Meat, cheese and small amounts of fat are fine, but avoid excessive liquid, oils and grease, and food that is already mouldy.
2. Press and seal. Push the contents down firmly to force out air pockets, then seal the lid straight away. Keep air out: opening the bin more than necessary slows fermentation and risks mould, and because the bucket stays sealed between additions it doesn't become the fruit-fly magnet an open caddy can.
3. Drain the liquid. Every couple of days open the tap and drain off the "bokashi tea". Left in the bucket it can turn the batch sour and slimy.
4. Repeat until full. A typical bucket takes about two weeks to fill with normal household food waste, depending on household size.
5. Seal and ferment. Once full, stop adding waste, seal the lid and leave it for around two weeks (10 to 14 days) while a second bucket takes over. Keep it somewhere warm and out of direct sunlight: fermentation runs slower in the cold, which is a real advantage of a method that lives indoors rather than in a garden bin through a Scottish winter. A working batch smells sweet-and-sour, like a takeaway or homebrew, and white mould on top is a normal sign of successful fermentation. Black or green mould means that batch has rotted rather than fermented; add more bran or start again.
6. Empty it. Add the contents to an outdoor compost heap or bin, or bury it in a trench in soil and cover it back over. Bury it properly: foxes and rats are drawn to buried meat and dairy if they can smell or dig it out, and a shared tenement back court is exactly where a rat problem is worth taking seriously.

Bokashi and ordinary composting

For anyone without a garden the appeal is a bucket that needs no outdoor footprint and is one of the only home methods that takes meat and dairy scraps rather than sending them to general waste.

The catch: fermented waste isn't compost

What comes out still looks largely like the food that went in: pickled, sour-smelling in the right way and structurally intact, because fermentation preserves rather than breaks down. Added to an active compost heap, it breaks down quickly into something recognisable as compost. Buried directly, leave the spot for about two weeks before planting, because the waste is acidic, with a slightly sweet, vinegar-like smell, and shouldn't touch plant roots straight away. That matters on ground that already leans acidic, as much Scottish ground does. The ground can also be frozen or waterlogged for weeks over a Scottish winter, which delays burial however ready the batch is. The fermented waste keeps sealed in its bucket for a while longer than the fermentation window requires, since it is already pickled, but keep a spare bucket or heap capacity for that stretch rather than assuming you can bury on demand.

Bokashi tea

The liquid has two uses. Heavily diluted with water it works as a liquid feed for established plants; the strength varies by source, so start weak and adjust.

Undiluted, it can be poured down a sink or drain to help keep it clear, a minor secondary use.

Downsides before you buy

• Ongoing cost. A starter kit typically runs £30 to £100, and the bran costs around £6 per kilogram, with an average household using about a kilogram every three months. Unlike a compost heap, it isn't free to run.
• It's a two-step process. A bin without a plan for the second stage, soil to bury into or a heap to add it to, leaves you with buckets of pickled scraps and nowhere to finish them.
• Limited value with no outdoor access at all. If there is no soil, no heap, no shared ground, no large container bed and no community plot, bokashi's advantage over simply reducing food waste shrinks. It is built for limited space, not none.

Why it matters in Scotland

A lot of Scots have no garden to compost in. At the 2011 census, 36.4% of Scottish households lived in flats. At the 2022 census 28% of Scotland's residents lived in flats, as did 56% of Edinburgh's residents, and 73% of Glasgow's households live in flats. Having no soil and no outdoor bin of your own is the everyday reality for a large share of Scottish households, not an edge case.

Bokashi removes the outdoor-space requirement for the fermentation stage, though not for the finishing one. A shared bit of garden ground, a large container of soil or a community growing plot all work, so check what is available locally, such as a shared tenement garden or a nearby allotment (composting in a flat covers the other options). The second bucket also needs somewhere to live: a kitchen cupboard, a hall press, or a stair landing if neighbours are on board, which matters on a shared stair where storage is tight.

Common questions

Sources