Category Archives: bokashi

compost cooked food waste using bokashi buckets and bran mix

Composting food waste

Research by WRAP (Waste and Resources Action Programme) shows that in the UK we are throwing away about one quarter of the food we buy, most of which could have been eaten. In effect, for every four bags of shopping we bring home, we put one straight into the bin.

Sending food waste to landfill is not only wasteful and expensive, but also produces emissions of methane as anaerobic bacteria break down the compressed waste. Methane is a potent greenhouse gas which, molecule for molecule over a century, traps 30 times more of the sun’s heat in the atmosphere than carbon dioxide.

EU regulations mean that the amount of biodegradable waste going to landfill is reducing, and many local councils now have green waste recycling schemes. This is an excellent solution, although you can’t dispose of any leftover meat, fish or cooked food waste this way, so those items still have to go to landfill.

If you have a garden a better way is to compost all your kitchen waste at home, producing rich fertile compost for the garden. Home composting has always been a good way of recycling uncooked kitchen waste such as vegetable peelings, egg shells, tea bags and coffee grounds.

But there is a problem dealing with meat and fish, dairy products and leftover cooked food. If you mix this waste in with your ordinary compost it smells and attracts flies and rats, so it needs to be composted in a different way. There are now several systems for doing this.

Food waste digesters

These are the simplest way to recycle all food waste, cooked or uncooked. There are two types of digester, the Green Cone and the Green Johanna, and both use natural processes to break the food down without producing methane.
turning2green.co.uk - green cone food waste digester
Green Cone – this small food digester needs to be installed in a sunny part of the garden as it uses solar heat to break down food waste into water, carbon dioxide, and just a small residue of solids. It isn’t suitable for garden waste, and doesn’t produce any compost. It’s easy to set up, very simple to use, rarely needs emptying, and it will dispose of most cooked and uncooked food waste. See Great Green Systems for more information or to buy.

Green Johanna food waste composterGreen Johanna. This is a more expensive option, but in my view it’s the best of all. It’s a very simple, easy to use compost bin which will dispose of all waste food and garden waste too.
It must be sited in a shady part of the garden and is designed to be filled with two parts food waste mixed with one third garden waste, working by a ‘hot composting’ method which produces good rich compost.

See also my post on Food waste digesters.

For more information or to buy see Great Green Systems or Amazon

 Wormeries

turning2green.co.uk - wormery for composting food wasteWorms are very effective and hygienic composters, and a wormery will compost most types of leftover food scraps, shredded newspapers, or even the contents of your vacuum cleaner, producing especially rich compost and concentrated liquid fertiliser. There are various designs available – the easiest to use have several layers of trays which the worms move up through leaving compost ready for use in the lower trays.

These are really good efficient systems, although the idea of dealing with worms doesn’t appeal to everyone. For more information see my page on Worm composting.or have a look at the different types available on Amazon

 Bokashi binsturning2green - bokashi bin for composting cooked food waste

This is a two step system in which the waste is firstly fermented in airtight bins and then composted, so it works along with a normal composting system, turning leftover meat, fish, bread, etc into nutrient rich compost without creating smells or attracting  flies or vermin.  As the materials are collected they are sprinkled with a bran based material, bokashi, which contains a culture of friendly micro organisms.  When the bokashi bin is full it is closed up and left for two weeks to ferment. Generally two containers are used so one can be left fermenting while the other is being filled. After fermentation the waste needs to be added to an ordinary compost bin or wormery or buried in the garden to complete the composting process.

There is more information on using this system on my Bokashi page, or see the equipment available at Amazon

DIY bokashi bins

Bokashi bins are used to process kitchen waste, including meat, fish, dairy products and cooked food, into a useful garden soil conditioner. The system uses a bran mixture infused with micro-organisms which is combined with the organic waste materials in a sealed container, and the contents are then fermented anaerobically. (See also my page on Bokashi)

The easiest way to begin bokashi composting is to buy a pair of purpose-made bins. These are usually made from recycled plastic and work really well (to buy see Blackwall Twin Pack Bokashi Bins) but home-made systems can work too. Catering size food containers are ideal and may be available at recycling centres, or suitable bins and taps can be purchased from home-brew supplies shops and home improvement stores.

It’s vital that containers have a good air-tight lid for the process to work properly. Also, the fermenting waste needs to be separated from any liquid draining through. A layer of absorbent material in the base will do this, but ideally there should be a reservoir in the bottom of the container below a drainage grid, plus a tap to draw off the liquid.

The most basic DIY option is simply an air-tight lidded bucket with no tap. It will do the job of fermenting the food waste, but will need 1-2 inches of shredded paper or sawdust in the bottom to soak up any liquid produced during the fermentation process, and all the waste added will need to be as dry as possible.

Adding a tap makes the best system – these can be purchased from home-brewing suppliers or garden centres. You will need to drill a hole in the bucket to fit the tap. Alternatively, use something like a home-brew fermenting bucket already fitted with a tap. An upturned plastic garden sieve would probably do the job as a drainage grid. Whatever you use, bear in mind it has to be retrieved from the gunk in the bucket each time it’s emptied, and it needs to be easily cleaned!

An alternative version uses two tightly nesting buckets.  Drill 20 to 30 small holes in the base of the inside bucket so liquid can drain through into the bottom bucket. Place a tight-fitting lid on the top bucket. This system has no tap, but the top bucket can be lifted off and any liquid that has collected in the bottom bucket can be poured off into a separate container. Here is a practical demonstration on YouTube.

Happy fermenting!

See also:  DIY bokashi bran; Bokashi; DIY worm bins

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