What is bokashi? Food scrap fermentation explained

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A sealed bucket under the sink, a few handfuls of bran boosted with EM-1 sprinkled over the peels, and leftovers that ferment instead of rotting: that's bokashi. The method intrigues people because it takes scraps that backyard compost piles and worms turn their noses up at, and because it fits in a kitchen. Understanding what goes on inside the bucket helps you avoid most beginner mistakes.

Bokashi: a Japanese word for matter "softened" by fermentation

The word bokashi is often translated as "fermented organic matter." It refers to the method, to the fermented material you end up with, and, by extension, to the bran used to start the fermentation.

In practice, kitchen bokashi relies on three things: an airtight bucket fitted with a grate and a spigot to drain off the liquid; your food scraps, pressed down layer by layer; and an activator, meaning cereal bran fermented with microorganisms. We cover the activator in detail in our guide to bokashi bran.

Did you know?

In Japanese, the verb bokasu means "to blur" or "to soften," the way you would blend a color gradient. Japanese gardeners use the word bokashi for a fertilizer made of rice bran and oilseed meal mixed with soil and then fermented: this "softens" the strength of these materials, making them gentler on roots.

Fermenting isn't composting: the pickle principle

Conventional compost is decomposition in the presence of air. Bacteria, fungi, and small critters consume the material while breathing oxygen; the pile heats up, loses water and carbon dioxide, and gradually turns into humus.

Bokashi follows an entirely different logic: preservation. In the sealed, tightly packed bucket, there's hardly any air left. The lactic acid bacteria introduced by the bran convert some of the sugars in the scraps into lactic acid. The environment becomes acidic, and that acidity holds back the microbes responsible for putrefaction. It's exactly what happens when you make pickles, sauerkraut, or the silage farmers feed their livestock in winter.

The result: your scraps aren't digested, they're preserved. They look more or less the same, take on a sour smell of vinegar or pickles, and are sometimes covered with a thin white film, which is a good sign.

Another difference from compost: a bokashi bucket barely warms up at all. Lactic fermentation releases very little energy compared with decomposition in air, and most of the material, and therefore most of the nutrients, stays in the bucket.

Who's at work in the bucket?

Bokashi activators are generally made with effective microorganisms, or EM. According to manufacturers, these blends mainly combine lactic acid bacteria, yeasts, and photosynthetic bacteria. You'll find their history and composition in our guide What are effective microorganisms.

In the bucket itself, lactic acid bacteria call the shots. The few published analyses of household buckets show that they make up the vast majority of the microbial population, both in the starter bran and in the bucket at full fermentation. Yeasts and other groups are far less prominent, and their exact role in bokashi is still poorly understood.

Their work shows up in the pH, meaning the level of acidity. The liquid drained from the spigot usually measures between about 3.5 and 5, an acidity comparable to orange juice or yogurt. That's why the contents of the bucket never go directly at the base of plants, and why the liquid is always heavily diluted.

The two stages of bokashi

Stage 1: fermentation in the bucket

You fill the bucket day by day, sprinkling each layer with bran and pressing it down firmly. Once the bucket is full, you leave it closed for at least two weeks in a room at a moderate temperature, draining off the liquid from time to time. Since this phase ties up the bucket, most people use two: one being filled while the other ferments. You'll find detailed instructions in our guide Starting your first bokashi bucket. In the diagram: fermentation in the bucket (1), then transformation in the soil (2).

Stage 2: transformation in the soil

What comes out of the bucket is an acidic pre-compost, not compost. It needs to go into the soil: bury it 8–12 in (20–30 cm) deep, well mixed with the soil, away from roots, and wait at least two weeks before planting. You can also mix it into a backyard composter or a large container of soil, or feed it in small amounts to worms, adding a few extra crushed eggshells to offset its acidity. In the soil, microbial life consumes the lactic acid, the acidity drops, and the scraps break down. Depending on the season and soil type, allow roughly two weeks to two months for them to disappear.

Key takeaways

Bokashi happens in two stages: a few weeks of fermentation in a sealed bucket, then transformation in the soil. Without that second stage, there's no compost.

Where does bokashi come from?

Fermenting organic matter before returning it to the soil is an old practice. It's often said to have roots in rural Korea and Japan, where organic matter was fermented to make a gentler fertilizer. These origins, however, are poorly documented.

The modern version, the kitchen bucket, is linked to Professor Teruo Higa, who taught horticulture in Okinawa, Japan. In the early 1980s, he developed effective microorganisms, a blend of fermentation microorganisms he proposed for agriculture. EM-inoculated bran, sprinkled over food scraps, then spread around the world, notably reaching Europe starting in the 1990s.

The real benefits and limitations

What bokashi does well

• It takes almost all food scraps, raw or cooked, including meat, fish, cheese, and citrus. The full list is in our guide What to put in a bokashi bucket.
• It fits in a kitchen: a 2.6–5.3 gallon (10–20 liter) bucket, with no contact with the soil.
• It preserves the material: since the bucket doesn't heat up and stays closed, relatively little material is lost as gas during fermentation.
• It takes little effort: chop, sprinkle, press down, close, drain the liquid. Nothing needs turning, and above all, you never stir.
• The smell stays faint with the lid closed. When you open it, it smells sour, like pickles, sometimes a little like beer or cider.

What to know before you buy

• It isn't finished compost: after two weeks, you have a pre-compost that still needs to go through the soil, a composter, or worms.
• You need an outlet: a yard, a container of soil, a composter, or a friend or family member who wants it.
• It uses activator continuously: you'll need to buy more or make your own.
• It doesn't take yard waste: grass clippings, dead leaves, and branches are still a job for the composter.
• It takes a little discipline: a bucket that's poorly sealed, too wet, or not sprinkled enough can rot instead of fermenting.

Emy's tip

Keep a small lidded container on the countertop during the day, and empty it into the bokashi bucket just once, in the evening. The less you open the bucket, the less air gets in, and the better the fermentation.

Is bokashi right for you?

Bokashi is a particularly good fit if:

• you have a yard, a vegetable garden, or large planters, and you want to return all your food scraps to them, including the ones a composter struggles to break down;
• you live in an apartment but have a regular outlet: a community garden, a friend's or family member's yard, a large planter on a balcony, a community compost drop-off;
• you already have a worm composter and are looking for a solution for meat, fish, and citrus.

It's less of a fit if you have nowhere to return the pre-compost to the soil. In that case, a worm bin, which produces a ready-to-use soil amendment, will often be simpler: our guide explains how a worm composter works. To compare the methods point by point, read our guide Bokashi, compost, or vermicompost.

To get started, all you need is an airtight bucket with a spigot, such as the Composteur à Bokashi Confort or the Skaza Organko 2 Bokashi Composter, plus our Bokashi EM Compost Activator, made on the farm. Finally, our guide Bokashi and EM: what the science says reviews the research.

In a nutshell

Bokashi is the lactic fermentation of food scraps, carried out in an airtight bucket using bran loaded with microorganisms. In about two weeks, the scraps turn acidic and are preserved rather than rotting, without heating up and with a faint, sour smell. This pre-compost then needs to go back into the soil, a composter, or a worm bin, where it finishes breaking down within a few weeks. Bokashi takes almost all food scraps in very little space, as long as you have an outlet and a supply of activator.

Related products

Best Seller

Bokashi Composter Confort

3.7-gallon (14-liter) capacity, sold individually or as a set of 2

$45.59 €40.83

Skaza Essential Bokashi Composter

4-gallon (15.3-liter) capacity, set of 2 buckets

$71.65 €64.17

Bokashi Composter Skaza Organko 2

2.5-gallon (9.6 L) capacity, sold individually or as a set of 2

$75.35 €67.49

Best Seller

Bokashi EM compost activator | 1 kg bag

Sold individually or in sets of 2 or 3 bags

$8.02 €7.18

Other topics in the guide

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