Compost, vermicompost, bokashi or EM: which method should you choose for your waste?

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Garden composter, wormery, bokashi bucket, effective microorganisms: when you want to make good use of your kitchen waste, there is no shortage of options, and the names can be confusing. Yet they don't all do the same thing, and they aren't aimed at the same households.

This guide will help you see things clearly in just a few minutes: how each method works, who it suits, what it produces and how to combine them. For a detailed head-to-head between a composter and a wormery, please see our guide Wormery or traditional composter.

Four approaches, two families: decomposing with air, or fermenting

Behind these four names there are really two main processes.

• Decomposition with air: bacteria, fungi and small creatures digest the material in the presence of oxygen. This is the principle behind garden compost and vermicomposting, in which compost worms do most of the work.
• Fermentation: in a sealed bucket, without air, microorganisms acidify the waste, rather like making sauerkraut. This is the principle behind bokashi. The result is not yet compost: it is a "pre-digested" material that then needs to be returned to the soil, to the compost or to the worms.

Effective microorganisms, or EM, are not a fifth method: they are microorganism preparations used to make bokashi activator or, as an extra, in a compost heap.

Traditional composting: who is it for?

This is the go-to method as soon as you have a patch of garden. Whether in a heap, a wooden or plastic bin, or a rotating composter, it accepts both kitchen waste and a good share of garden waste: grass clippings, leaves, shredded prunings. That is its great strength: no other method can take in so much volume.

On the other hand, it needs outdoor space, contact with the soil (except for rotating models) and time. It suits houses with gardens, families who cook a lot of fresh produce and anyone who wants a soil improver for their vegetable patch. We describe the different types of equipment in our guide Compost heap or compost bin, and the special case of the drum in our guide Rotating composter.

Vermicomposting: the solution for flats

In a wormery, compost worms (Eisenia, which are different from garden earthworms) eat kitchen waste and produce a very fine vermicompost as well as a liquid fertiliser. The process doesn't heat up and doesn't smell when properly managed, so it can be set up in a kitchen, a utility room or on a balcony. In fact, it is the solution we recommend first and foremost to people living in flats.

To give you an idea of scale, around 500 worms are estimated to digest roughly a hundred grams of waste a day. A wormery such as our WORMbox wormery is therefore suitable for a household's kitchen waste, but not for grass clippings or branches. Worms also have their preferences: our guide explains how a wormery works and what they accept.

Bokashi: ferment, then finish in the soil or the composter

Bokashi is an airtight bucket into which you press down your kitchen waste, sprinkling each layer with fermented cereal bran, such as our Bokashi EM compost activator. After a few weeks the waste has fermented, and along the way you collect a liquid that can be used diluted.

Its advantages: it fits under the sink, needs almost no maintenance and accepts leftovers that garden compost and worms struggle with, such as small amounts of meat, fish or dairy. Its limitation, which is important to understand: what comes out of the bucket is not finished compost. You need to bury it in the soil, mix it into compost or feed it gradually to worms so that the transformation can be completed. Everything is explained in our bokashi guide.

Effective microorganisms (EM): a supplement, not a method

EM are blends of microorganisms sold in liquid form, such as the EM-1 stock solution. According to the manufacturers, they mainly combine lactic acid bacteria, yeasts and photosynthetic bacteria; the stated composition also varies from product to product. They are mainly used to make bokashi activator, and some gardeners use them as a light watering on a compost heap that is just getting started or that smells bad.

Let's be honest: a compost heap with a good balance of green and brown materials, sufficiently aerated and moist, needs no additive to work. EM can help in certain situations, but they don't replace a composter, a wormery or a bokashi. To find out more, Emy, our effective microorganisms mascot, takes you through our guide to effective microorganisms: their uses in the garden, in the home or with animals, and what is actually known about them.

Did you know?

Bokashi and garden compost aren't opposites: the first ferments, the second decomposes. By emptying your bokashi bucket into your composter, you get the benefits of both, and the tricky leftovers are already acidified by the time they reach the garden.

The comparison at a glance

The times below are rough estimates: they vary considerably depending on the season and on maintenance.

Garden composter (bin or heap)

• Time: 4 to 9 months in a bin for ready-to-use compost, 6 to 12 months in a heap.
• Space: a corner of the garden, on soil.
• Waste: kitchen and garden, in large volumes.
• Result: compost to spread on the vegetable patch, in the orchard or in flower beds.

Rotating composter

• Time: around 6 weeks for compost that is still fresh, followed by 3 to 5 months of maturing in a heap.
• Space: a terrace or a yard, even a concreted one.
• Waste: kitchen waste and small garden waste, no branches.
• Result: fresh compost to leave to mature before use.

Wormery

• Time: around 4 months, with a ready-to-use product.
• Space: a few tens of centimetres of floor space, indoors or under shelter.
• Waste: mainly raw kitchen waste, in moderate quantities.
• Result: concentrated vermicompost and a liquid fertiliser.

Bokashi

• Time: around 3 weeks of fermentation, followed by a finishing stage in the soil or in the compost.
• Space: a bucket in the kitchen.
• Waste: almost all kitchen leftovers, including small amounts of meat and dairy.
• Result: a pre-compost to bury or compost, and a liquid to dilute.

Effective microorganisms

• No time frame or equipment of their own: they are an ingredient of bokashi and an optional supplement for compost.

Combining them: bokashi + compost, compost + worms

Many households don't have to choose just one method. Some combinations work particularly well:

• Bokashi and composter: the bucket stays in the kitchen and takes all the leftovers, then its fermented contents go into the composter, where decomposition is completed.
• Composter and wormery: the composter takes the garden waste, while the wormery processes peelings close to the kitchen, even in winter.
• Bokashi and wormery: for city dwellers, bokashi makes it possible to process the leftovers that worms don't like, then feed them the pre-compost in small amounts.

Key points

Garden and large volumes: the composter. Flat: the wormery. Tricky leftovers or very little space: bokashi, to be finished in soil, compost or with worms. As for EM, they remain a helping hand.

In summary

Compost and vermicompost break down waste with air, bokashi ferments it in a closed container, and EM are supplementary microorganisms rather than a method in their own right. If you have a garden, the composter remains the foundation, possibly complemented by a bokashi for tricky leftovers. In a flat, the wormery is the most complete solution, and bokashi is a good ally as long as you plan where to finish its contents. Choose according to your home, your waste and the time you want to devote to it: there is no bad method, only methods that are more or less suited to you.

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Other topics in the guide

Vermicomposting30 sheets →Bokashi24 sheets →EM micro-organisms26 sheets →