Composting Kitchen Waste: Bokashi and Caddies

A normal compost heap is brilliant for vegetable peelings, but there is one rule that trips up almost every beginner: an open heap cannot safely take cooked food, meat, fish or dairy. Those scraps attract rats and other vermin, and they turn a tidy heap into a smelly mess. The good news is that the very waste your heap can't handle is easy to compost a different way — with a bokashi bin, a kitchen caddy and your council collection, a hot composter, or a wormery.

So if you've been throwing chicken bones, leftover pasta and cheese rinds in the bin and feeling guilty about it, this guide sorts it out. We'll cover what genuinely works, in UK kitchens, without any of the usual myths. For the basics of building and managing an outdoor heap, see our main guide to how to make compost — this article is the kitchen-waste companion to it.

Why kitchen waste is a problem in open compost

Raw fruit and veg trimmings, tea, coffee grounds and crushed-up cardboard are exactly what an open compost bin wants. They rot down cleanly and feed the heap. The trouble starts with the food that's been cooked or comes from animals.

Cooked food, meat, fish, dairy, oily leftovers and bread all break down in a way that smells strongly and stays attractive to pests for weeks. In a typical UK garden that means rats, mice and flies — and once rats find a reliable food source, they're hard to move on. An ordinary "dalek"-style cone bin sitting open on the soil simply can't keep them out.

That's why the standard advice is to keep these items out of any open heap or council garden-waste bin. We go through the full list of what's safe and what isn't in what you can and cannot compost — it's worth a read before you start, because the line between "fine" and "vermin magnet" isn't always obvious. Eggshells, for example, are fine to add but break down extremely slowly, so don't expect them to do much; they're best thought of as a slow soil amendment rather than a feed.

The rest of this guide is the answer to "so where does it go?"

Bokashi bins: ferment everything, even the bones

Bokashi is the one method that takes genuinely all your food waste — including the cooked food, meat, fish and dairy that nothing else on an open heap will tolerate. It's the workhorse of a small UK kitchen.

Here's the trick: bokashi doesn't rot your food, it ferments it, more like pickling. You use a sealed, airtight bucket and sprinkle each layer of scraps with "bokashi bran" — bran that's been inoculated with effective microbes (often sold as EM). Starved of oxygen, those microbes pickle the waste rather than letting it decay. Because nothing is rotting in the open air, there's no foul smell (fermented bokashi has a sweetish, slightly vinegary, sourdough-ish smell) and nothing to attract rats or flies.

How to run a bokashi bin:

1. Add food scraps as you produce them — peelings, plate scrapings, cooked leftovers, small bones, cheese, the lot. Chop bulky bits down a little.
2. Sprinkle a small handful of bokashi bran over each new layer.
3. Press the waste down to squeeze out air, then seal the lid firmly. The airless environment is what makes it work.
4. Every few days, drain off the liquid (more on that below).
5. When the bin is full, leave it sealed for about two weeks to finish fermenting while you fill a second bin.

Two bins working in rotation is the sensible setup — one filling, one resting.

The bokashi liquid (and what it's actually good for)

As the waste ferments, it releases a liquid that collects in the base. Most bokashi bins have a tap at the bottom so you can drain it off every two or three days — do drain it, or the bin can go anaerobic in a bad way and smell.

This liquid (sometimes called bokashi "tea") is genuinely useful, with two honest uses:

• As a diluted plant feed: dilute it heavily — roughly 1 part liquid to 100 parts water — and water it onto soil around plants. It's mildly nutritious and the microbes are good for soil life. Use it fresh, within a day, as it doesn't keep.
• Down the drain: undiluted, it's an excellent natural drain cleaner — the microbes help keep sink and toilet pipes clear.

Don't overstate it as a fertiliser — it's a useful by-product, not a miracle feed. For a proper homemade liquid feed, comfrey and nettle teas are far stronger.

Finishing the bokashi off

Fermented bokashi waste is not finished compost. Open the bin after a couple of weeks and you'll find your scraps largely intact but pickled — pale, slightly soft, smelling sour rather than rotten. That's exactly right.

To finish it, you do one of two things:

• Bury it in a spare patch of soil or an empty bed, about 20cm down, and cover it over. It breaks down completely in two to four weeks, feeding the soil directly. Keep it away from plant roots for the first couple of weeks, as fresh bokashi is acidic.
• Add it to your compost heap. Fermented waste integrates safely into an ordinary heap — the pickling has already neutralised the vermin risk — and it actually speeds the heap up. This is the neat link back to how to make compost: bokashi handles the food an open heap can't, then hands the result over to that heap to finish.

If you garden no-dig, burying small amounts under the compost mulch works well too; see no-dig gardening for how that bed structure works.

Once you've explained the method to yourself, the kit is simple — a bokashi bin (ideally a pair) plus a sack of bran:

Kitchen caddies and council food-waste collections

The simplest route of all needs no garden and no maintenance: your council food-waste collection. Most UK councils now provide (or will soon, under the rollout of separate weekly food-waste collections in England) a small kitchen caddy and a larger kerbside bin for food scraps.

The kitchen caddy is the little lidded bin that sits on your worktop. You line it with newspaper or a certified compostable liner (look for the seedling logo — ordinary plastic bags aren't accepted), fill it with all your food waste, and tip it into the outdoor food bin for collection. Crucially, council food-waste collections accept cooked food, meat, fish, dairy and bones — the very things your garden heap can't. The council sends it for industrial composting or anaerobic digestion, which runs hot enough to deal with it safely.

A few practical pointers:

• Keep the caddy lid shut and empty it every couple of days to avoid fruit flies.
• A sheet of newspaper in the base soaks up moisture and keeps it cleaner.
• Check your own council's list — rules on liners and exactly what's accepted vary by area.

This is the no-effort option, and there's no shame in using it for the awkward stuff while composting your peelings at home. Many growers run both: a heap for the garden-friendly waste, the caddy for everything else.

Hot composters: cooked food at home

If you'd rather keep all your waste on site and make your own compost from it — including cooked leftovers — a hot composter is the answer. These are insulated, sealed units that get hot enough (often 40–60°C) to break food down quickly and to deter vermin, which an open cold heap can't manage.

Two well-known UK options:

• The Green Johanna — an insulated, partly sealed plastic bin designed specifically to take cooked food, meat and fish alongside garden and kitchen waste. It comes with an optional "winter jacket" to keep it working through cold UK months. It's a warm heap rather than a fiercely hot one, so you still add it to soil only once it's properly composted.
• The HotBin — a heavily insulated bin that genuinely runs hot (up to around 60°C) and composts much faster, in weeks rather than months. It handles cooked food and even small amounts of bones, and the heat kills weed seeds. It needs a steady supply of waste and a bit of attention to airflow to keep the temperature up.

Both cost more upfront than a basic bin, but they let you compost your whole household's food waste at home and produce usable compost from it. For a busy household that hates the idea of binning scraps, they pay their way. If you're weighing up where compost fits in your wider plan, our guide to starting a vegetable garden puts soil-building in context.

Wormeries and trench composting as alternatives

Two more home methods round out your options, each suited to different kitchen-waste habits.

A wormery is a tiered bin of composting worms (tiger worms, not earthworms) that eat your raw kitchen scraps and turn them into rich worm compost plus a liquid feed. It's compact, suits a balcony or shed, and produces some of the best soil improver going. The catch: worms are fussy. Keep meat, fish, dairy and large amounts of cooked or citrus waste out of a wormery — those are bokashi or hot-bin jobs. Feed a wormery mainly raw veg peelings, in modest amounts the worms can keep up with. We cover setup, feeding and troubleshooting in our full guide to running a wormery.

Trench composting is the simplest method of all and needs no kit. You dig a trench or a hole about 30cm deep, drop in raw kitchen scraps (peelings, not meat or cooked food on an open trench), cover them with soil, and let them rot in place over a few weeks. It works brilliantly along a bean or courgette row: dig the trench in late winter, fill it gradually, cover it, and plant hungry crops like runner beans or courgettes over the top in spring. The rotting scraps hold moisture and feed the roots exactly where they're needed. Interestingly, fermented bokashi waste can also be trenched this way to finish off — so the methods join up.

Choosing your method

You don't have to pick just one — most home growers end up combining them:

• Raw veg peelings, tea, coffee grounds → open heap (see how to make compost) or a wormery.
• Cooked food, meat, fish, dairy, bones → bokashi, a hot composter (Green Johanna / HotBin), or your council food caddy.
• No garden or no time → council food-waste collection, every time.
• A bean or courgette bed coming up → trench composting for the raw stuff.

The thread running through all of it: nothing cooked or animal-based goes in an open heap, but with bokashi and a caddy you never have to bin it either. Get those two going and you'll compost almost everything your kitchen produces — and your soil, and your veg, will be the better for it.