Bokashi and wormeries: how to feed fermented bokashi to your worms without making the bin too acidic

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Do you already have a wormery and are wondering whether to add a bokashi bucket? Or the other way round? The two methods complement each other well, especially in a flat: bokashi takes the leftovers worms don't like, and the worms can then finish the job on the fermented pre-compost.

But combining them takes a little finesse. Bokashi is acidic, and worms like a neutral environment. Here is how to make the two coexist without putting your colony under strain, and what you can honestly expect from it.

Why combine the two methods

A wormery feeds mainly on peelings. Meat, fish, dairy, dishes with sauce or large amounts of citrus fruit have no place in it, as we explain in our guide What should you feed your worms?. A bokashi bucket, on the other hand, accepts most of these leftovers.

By combining the two, you can make use of almost all your kitchen waste without a garden:

• peelings and coffee grounds go straight to the worms;
• meal leftovers, meat and fish in small pieces, and citrus fruit go into the bokashi;
• some of the fermented bokashi then goes into the wormery, a little at a time.

If you don't have one yet, a tray model such as the WORMbox wormery lends itself well to this combination, as it is easy to set aside a corner for bokashi. Bokashi also has an advantage for worms: the material has already been softened by fermentation, so it is easy to break down for the micro-organisms the worms feed on.

The problem: acidity and salt

Compost worms thrive in an environment with a pH close to neutral, between 7 and 8. Fermented bokashi, however, is very acidic: its liquid has a pH of 3.5 to 4.9 depending on the measurements. Added in large quantities, it causes the pH of all the bedding to drop, and the worms can no longer get away from it.

Worms can nevertheless cope with acidic food, on one condition: they must be able to avoid it. Placed in a corner, the bokashi is ignored at first for a few days, sometimes one to two weeks, while its acidity falls through contact with the bedding. Then the worms move closer and eat it.

Another thing to watch: salt. Leftovers from cooked dishes make bokashi saltier, and salt dehydrates worms. In a field trial comparing worms fed with or without bokashi, the "bokashi" samples were indeed richer in sodium. In the diagram: a bed of dry cardboard (1), a small portion of bokashi (2) and crushed eggshells (3), in just one corner of the tray.

Did you know?

One practitioner who tipped too much bokashi into an indoor wormery in one go saw the whole bin turn sour. The same bokashi, given in smaller amounts to a large outdoor bin, was eaten quickly. So it is all a question of dose.

The method: small amounts, in one corner, on dry bedding

1. Choose a mainly plant-based bucket. If your bucket contains mostly meat, dairy, fat or salty leftovers, it is better to bury it or put it on the compost heap.
2. Drain the bokashi well: never pour the liquid from the bucket into the wormery.
3. Prepare a refuge: in one corner of the active tray, spread a layer of dry bedding, shredded brown cardboard or newspaper. It absorbs moisture and acts as a buffer zone.
4. Add a small amount of bokashi on top of this bedding, about a small bowlful to start with, never the whole bucket. No source gives a precise dose: this is a cautious starting point, to be adjusted to the size of your bin.
5. Sprinkle with crushed eggshells, or our RegulaWorm, to help correct the acidity.
6. Cover with a little dry bedding or a sheet of damp cardboard.
7. Wait until it has been eaten before adding more bokashi, and carry on feeding the worms as usual elsewhere in the bin.

Gradually increase the amounts while watching your worms. The rest of the bucket can wait, closed, for several weeks, or go into a soil bin as explained in our guide No garden? What to do with your bokashi.

Emy's tip

Mix the bokashi with at least the same amount of shredded cardboard, newspaper or coir before adding it to the bin. This bedding absorbs excess moisture, dilutes the acidity and gives the worms material they enjoy.

A gentler alternative: let it mature first

If your worms are sensitive, or if you are just starting out, first leave the bokashi in a soil bin for two to three weeks. Its acidity drops, it partly breaks down, and you can then give it to the worms without any risk of upsetting the balance. It takes longer, but it is the safest method.

Correcting acidity: eggshells and calcium carbonate

Crushed eggshells are the simplest corrector: dried, then ground to a powder, they gradually dissolve in contact with the acidic environment. Our RegulaWorm, a 100% natural limed blend designed for wormeries, works faster: one tablespoon a week is enough, and it is a good solution if you don't eat eggs. Other practitioners use a gentle limestone soil improver, such as dolomite or agricultural lime (calcium carbonate), in small amounts.

Never use quicklime or building lime: they are caustic to worms and micro-organisms. And there is no need to try to neutralise the whole bucket: one corner of the bin and good bedding are enough in most cases.

Signs that things are going well, or badly

All is well

• After a few days, the worms gather under and in the bokashi.
• The sour smell fades within a few days, and the bin smells of woodland floor again.
• The bokashi turns into a dark material, like the rest of the vermicompost.

Time to act

• The worms climb up the sides or flee the tray.
• A sour or rotten smell lingers throughout the bin.
• The bedding becomes waterlogged, or fruit flies multiply.

If so, stop the bokashi, remove anything that hasn't been eaten, and add a good layer of dry bedding and crushed eggshells. Our guide Worms escaping from the wormery explains the steps to restore the balance.

What research says: results still inconclusive

Bokashi is often presented as a way to obtain an "enriched" vermicompost. The data do not support this claim. A field trial carried out over several seasons, comparing worms fed with or without bokashi, found the results inconclusive. The vermicompost from bokashi was even slightly lower in calcium, magnesium and potassium, it contained more sodium, and the authors felt the benefit might not justify the extra cost and work.

Our takeaway: combining bokashi and worms is above all a practical way to make use of more waste without a garden, not a recipe for better vermicompost. If you can only choose one method for your peelings, the wormery remains the most complete, as we explain in our guide Bokashi, compost or vermicompost: which method should you choose?.

Key points

Bokashi and worms get along well in small doses: drained, mainly plant-based bokashi, placed in one corner on dry bedding, with crushed eggshells, and never more than the worms can eat in a few days.

In summary

Bokashi lets you deal with the leftovers worms refuse, and the worms can then finish off part of the pre-compost. The key is moderation: bokashi is acidic and sometimes salty, so give it in small amounts, in one corner of the bin, on dry bedding, with crushed eggshells. Watch your worms, increase gradually, and use a soil bin if you want to play it safe. This way you will make use of almost all your kitchen waste, without any promise of a richer vermicompost.

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Other topics in the guide

Vermicomposting30 sheets →Composting25 sheets →EM micro-organisms26 sheets →