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

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Do you already have a worm composter and are wondering whether to add a bokashi bucket? Or the other way around? The two methods work well together, especially in an apartment: 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's how to make the two coexist without putting your colony under stress, and what you can honestly expect from it.

Why combine the two methods

A worm bin runs mainly on peels and food scraps. Meat, fish, dairy, dishes with sauce, or large amounts of citrus 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 recycle almost all your food scraps without a yard:

• peels and coffee grounds go straight to the worms;
• meal leftovers, meat and fish cut into small pieces, and citrus go into the bokashi;
• some of the fermented bokashi then goes into the worm composter, a little at a time.

If you don't have one yet, a tray model such as the WORMbox worm composter lends itself well to this combination, since it's 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's easy to break down for the microorganisms the worms feed on.

The problem: acidity and salt

Composting 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 lowers the pH of all the bedding, and the worms have nowhere left to escape it.

Worms can still 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 drops through contact with the bedding. Then the worms move in and eat it.

Another thing to watch: salt. Leftovers from cooked dishes make bokashi saltier, and salt dehydrates worms. In fact, in a field trial comparing worms fed with or without bokashi, the "bokashi" samples were higher 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 composter who dumped too much bokashi into an indoor worm bin all at once watched the whole bin turn sour. The same bokashi, given in smaller amounts to a large outdoor bin, was eaten quickly. So it all comes down to the dose.

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

1. Choose a mostly plant-based bucket. If your bucket contains mostly meat, dairy, fat, or salty leftovers, it's better to bury it or add it to your compost pile.
2. Drain the bokashi well: never pour the liquid from the bucket into the worm composter.
3. Prepare a refuge: in one corner of the active tray, spread a layer of dry bedding, such as 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, 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 keep feeding the worms as usual elsewhere in the bin.

Gradually increase the amounts while keeping an eye on 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 yard? What to do with your bokashi.

Emy's tip

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

A gentler alternative: let it mature first

If your worms are sensitive, or if you're 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 throwing the bin off balance. It takes longer, but it's the safest method.

Correcting acidity: eggshells and calcium carbonate

Crushed eggshells are the simplest fix: dried, then ground into a powder, they gradually dissolve in contact with the acidic environment. Our RegulaWorm, a 100% natural lime-based blend designed for worm composters, works faster: one tablespoon a week is enough, and it's a good solution if you don't eat eggs. Other composters use a mild liming amendment, such as dolomitic lime or agricultural lime (calcium carbonate), in small amounts.

Never use quicklime or construction lime: they are caustic to worms and microorganisms. And there's no need to try to neutralize 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 inside the bokashi.
• The sour smell fades within a few days, and the bin smells like the forest floor again.
• The bokashi turns into dark material, like the rest of the vermicompost.

Time to act

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

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

What the research says: results still inconclusive

Bokashi is often presented as a way to get "enriched" vermicompost. The data don't support that claim. A field trial conducted over several seasons, comparing worms fed with or without bokashi, found the results inconclusive. The vermicompost made with bokashi was actually slightly lower in calcium, magnesium, and potassium and 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 recycle more food scraps without a yard, not a recipe for better vermicompost. If you can only choose one method for your peels and scraps, the worm composter remains the most complete, as we explain in our guide Bokashi, compost, or vermicompost: which method should you choose?.

Key takeaways

Bokashi and worms get along well in small doses: drained, mostly 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 handle 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 go through a soil bin if you want to play it safe. This way, you'll recycle almost all your food scraps, though without any promise of richer vermicompost.

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Other topics in the guide

Vermicomposting30 fact sheets →Composting25 fact sheets →EM microorganisms26 fact sheets →