Bokashi Composting Food

The normal advice is that cooked food should not be composted in a conventional cold compos bin or heap as it may attract rats. While there are bins available for the hot composting of cooked food they tend to be expensive so in order to discourage home composters sending cooked food waste to landfill I have been photographing the use of a Bokashi bin as a means of treating the food so as to make it suitable for cold composting. This system can also be used where the Council has a kerbside food waste collection, but the householder does not want to store the food for a week between collections.

I started recording the use of a commercially available Bokashi bin to turn waste food into fermented pre-compost suitable for adding to a conventional compost bin or burying in the garden just before Christmas. The bin was filled, the lid secured to prevent access of air  and put a side for the fermentation process to start on the 5^th January. It would normally be left for two or three weeks and todays photo show the start of white fungal growth on the surface of the fermenting material. The growth of white mould is acceptable. However,  a green or black fungal growth indicates that things have gone wrong.  As on this occasion I want further photographs of the mould developing the bin was quickly resealed and will be left for a further few days.

More information can be seen on previous blogs or at http://www.carryoncomposting.com/416920212

The Bokashi page at www.carryoncomposting has been updated to include details of largewr bins.

Domestic Bokashi Bins are available in the UK in a range of sizes, a quick search on the web will show bins of  15 litre, 18 litre, 23 litre, 27 litre, 30 litre (stainless).   A pair of bins are normally used so that when the first bin has been  filled and is  fermenting a second bin is available to take the current waste.

 However,  commercial size Bokashi bins are avialable. The 120 litre wheelie bin style Boakashi  from www.mygreenchapter.com ( My Green Chapter is a Dubai-based online garden centre & pet store)  is  big enough for small businesses, schools and nurseries. This offers such establishments an alternative to aerobic composting and participation in kerbside food collection schemes. As with other Bokashi systems  it can be used to ferment  vegetable, fruit, meat, fish and dairy products to make environmentally friendly pre-compost for office communal areas or school gardens. 

The 120 litre Bokashi bins shown in the photos are  available from a company based in Cornwall (https://www.wiltonecostore.co.uk/) and are suitable for medium to large scale use. The bins are   shown in one of the photos being used in a bank of six. 

Seaweed contains plant nutrients, including potassium, (up to 12%), but it is  low in nitrogen and phosphate. It can   contain in the region of  60 trace elements, growth hormones and other nutrients and is  particularly rich in iodine and calcium.   Spraying seaweed tea on plants  is said to increase resistance to insect infestation.

Seaweed has been used as a soil improver for centuries and is still used in the garden as a mulch, liquid feed and in making  compost.   It is also available commercially both dried and as a liquid.  

Composting seaweed

Seaweed is a commonly used as a  constituent in home composting  in coastal areas. It acts as an activator speeding up the compost process. If using a cold composting technique  small quantities of seaweed  can just be added to the bin  in the same way as any other nitrogen rich  “green”. There are mixed views as to whether the seaweed should be washed to remove traces of  saltwater or sand with the consensus being that it is not necessary. However, not all plants tolerate salt so if in doubt the seaweed should be rinsed  in fresh water.

If using a New Zealand or pallet bin, in which layers of greens and browns are alternated, the seaweed can be added as a separate green layer or mixed with  other green material. Shredded or chopped seaweed cut in   1- or 2-inch will decompose in  a few weeks compared with  six months or more for uncut fronds so, as with other materials, it is better to cut the seaweed into small pieces. If the contents of the bin are to be turned to aerate the organic material occasionally in cold composting  or regularly as in hot composting cutting the seaweed into short lengths will also make it easier to turn during aeration and speed up the composting process.  

Seaweed can also be trench composted and used to make liquid feed. Details are available at carryoncomposting.com

If considering collecting seaweed it must be noted that many countries have laws or regulations protecting the marine environment and it is likely that these will cover the harvesting of seaweed. Please check.

The use of a Bokashi bin  to turn cooked food into a fermented pre-compost that can be added to a normal compost bin provides a relatively cheap way of composting cooked food waste without attracting rats. It also offers a way of replacing a potentially smelly kitchen caddy with the not unpleasant smell of Bokashi Bran and replaces the task of   tipping untreated food from a caddy into the compost bin or the Food Waste bin (where the council offers a weekly food waste collection) with  that of tipping pickled food into the compost bin.

As a bonus during the fermenting process, the Bokashi bin will produce a liquid known as ‘Bokashi tea’ or “Bokashi juice” which needs to be drained off every 2-3 days. The juice will be a reddish, orangey colour with a  vinegar  or slightly fruity smell. There may be a thin white coating on the surface or white fungal threads floating in the liquid.

This  liquid  contains Nitrogen, Phosphorous, and Potassium plus  other nutrients (which may include boron, chlorine, iron,  manganese & zinc) and microorganisms,  from the food waste making it  a good liquid feed or plant  fertilizer  and soil enhancer.( Click  Bokashi bins)   The juice is diluted 1-part juice :100 parts water for bare soil. Earthprobiotic.co.za are more specific in their examples of recommended concentrations for different applications  suggesting 1:100 for lawns, 1:300 for gardens and pot plants, 1:500 for succulents and 1:1000 for any sensitive plants.

The diluted juice can be sprayed or watered onto the soil using a watering can fitted with a rose including the soil  around plants. It is acidic and should not be allowed to touch the  foliage at this concentration although other sources suggests that a dilution of 1:500 or a dilution of between  1: 500 – 1: 000 for spraying onto foliage.

For information and links to other sites at http://www.carryoncomposting.com/416920212

The Bokashi bin started before Christmas is now full and will be set aside for two weeks to ferment. During the fermentation process more Bokashi juice will be produced.

I have used this single bin to deal with the food waste from a family of two adults. hopefully the next Bokashi post will show the fermented product with while fungal mould growing on the surface.