Compost makers: Bokashi bins

 

In my compost repertoire I have two Bokashi bins, which I’ve been using for over 10 years . These are a Japanese invention, originally designed to quickly neutralise the smells, and condense the volume, of kitchen waste in the bijou homes of Tokyo.

As a result of what is, essentially, a speeded-up fermentation process, they have been subsequently been marketed as ideal compost-starters for small gardens. Where a compost heap might be unsightly or too close to the house for comfort, a Bokashi bin can be discreetly tucked away under a potting bench or outside the back door.

So, how does it work?

By layering kitchen waste with a sprinkling of a special microbe-infused bran, and sealing it in an air-tight bin, the contents quickly start to ferment into an inoffensive pickle. Each time you add a fresh layer of waste another handful of bran is added, and the stack is pressed down to remove as much air as possible before resealing with a tight lid. When the bin is eventually filled it is left for several weeks, after which it is safe to tip it out and dig it into the soil to quickly integrate. Unlike ‘normal’ decomposition (rotting down with air, heat and the activity of bacteria, slugs and worms), fermented compost doesn’t appear to change its appearance that much. This can be a bit disconcerting when you first tip it out, as it looks more like a giant lasagne that would surely attract rats! But, miraculously, it can be dug into the garden without fear of smells or interest from vermin. Once dug in, it will very quickly be incorporated by worms into the soil, and will have ‘neutralised’, ready to plant in after about three to four weeks.

Because it needs to be buried, I use mine in an area I’ve designated that season for hungry plants, like courgettes or runner beans, so other planting isn’t disturbed by digging it in. I use my worm compost, mixed with spent pot soil, as a top mulch in more crowded areas.

In addition to the bulky contents, a useful ‘tea’ can be harvested via the taps. This is a very concentrated brew (it can be used neat as an effective drain unblocker!) so needs watering down before using as a plant feed in pots and beds.

I use two Bokashi bins in tandem, as once one is full you need to wait a few weeks for fermentation to complete before emptying it. I tend to fill them with everything that can’t be put, or won’t fit,  in the wormeries. Fish skins and bones, any left over cooked food, an excess of green peelings, leaves or chopped up cabbage stalks… Anything apart from bulky bones. I also don’t add fats (eg cheese rind, oil), although, allegedly, you can.

In theory, because the bins are sealed, you can keep them in the kitchen, but mine are too old and messy for that (and my kitchen too tiny), so I keep them outside.

Here’s one I emptied a few weeks ago, adding the contents to a trench I’d dug in a raised bed. I covered it over with soil, and this is where, once the weather warms up, I’ll be planting the hungry runner beans.

If you’re interested in learning more, here’s a couple of links to some Bokashi bin retailers in the UK:

Wriggly Wigglers   Bokashi Direct

Do you use Bokashi bins in your garden?

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