What is bokashi, and does it actually work?

The disappointment with bokashi almost always comes from expecting compost out of the bucket. What comes out looks much like what went in, only paler and smelling strongly of vinegar and pickle. That is the process working correctly. The breakdown happens afterwards, in soil, and it happens fast.

What you'll need

• A bokashi bin with a tap and a tight lid
• Bokashi bran or inoculant
• Somewhere to bury the output — a trench, a spare bed or a compost heap
• A second bucket so one can rest while the other fills (optional)

Step by step

1. Understand what it is for.It handles the waste an open heap cannot: cooked food, meat, fish, dairy, bread. In a flat, a small garden or anywhere rats are a problem, that is its whole value.
2. Layer waste with bran and press it down.A scattering of bran over each addition, then press the waste down firmly with a plate or a masher. Air is the enemy here, which is the opposite of a compost heap.
3. Keep the lid sealed between additions.The process is anaerobic. Every opening slows it, so add once a day rather than continuously and close it properly each time.
4. Drain the liquid every few days.The tap at the base draws off a strong acidic liquid. Diluted heavily — around a hundred to one — it is a plant feed; undiluted, it is a good drain cleaner. It goes off quickly, so use it fresh.
5. Leave a full bucket to ferment for two weeks.Sealed and undisturbed. This is why two buckets are useful: one ferments while the other fills.
6. Check what success looks like.White threads of mould are correct and expected. A strong sweet-sour pickle smell is correct. Green, blue or black mould and a putrid smell mean it has gone wrong, usually from too much air or not enough bran.
7. Bury the output, and this is the step that matters.Dig it into a trench about 200mm deep in a spare piece of ground, or mix it into the middle of an active compost heap. In soil it disappears within two to six weeks depending on the season.
8. Wait before planting into it.It is strongly acidic when buried. Give it at least two to four weeks, and longer in cold weather, before planting into that ground, or roots will be scorched.
9. Site the trench thoughtfully.Where buried food waste will not be dug up by a dog or a fox — a trench in a vegetable bed covered properly, or the middle of a working compost heap.

Tips

• Two buckets is not optional in practice. One filling, one fermenting.
• The liquid goes off within a day or two of draining. Use it or pour it down the drain, where it does no harm at all.
• In a flat with no ground at all, bokashi output can go into a large tub of soil that becomes usable potting soil after a couple of months — but there does have to be soil somewhere in the chain.

Common mistakes

• Expecting compost out of the bucket — Fermented waste still looks like waste. The transformation happens in soil, in the two to six weeks after burying.
• Planting straight into freshly buried bokashi — It is very acidic at that point and will scorch roots. Give it a few weeks.
• Opening the bin every time something is thrown away — Air disrupts the fermentation. Collect in a caddy and transfer once a day.
• Not pressing the waste down — Trapped air pockets go mouldy and putrid rather than fermenting cleanly.

Questions people ask