Composting with Bokashi Bins
The domestic Bokashi composting system originated in Japan and offers a means of reducing food waste sent to landfill. Materials such as eggshells and bones will also be decomposed but they will take much longer to breakdown and are probably best treated using a food digester such as the Green Cone.
The Bokaski is a useful system for those without a garden or who want to convert cooked food waste into a material that can be composted in a conventional compost bin.
Bokashi bins can be kept in the kitchen or outside in a shed or garden. However, in colder conditions the fermentation process slows down, so it should be left to digest for a longer period (e.g. for three weeks or more instead of two). If kept outside the house an outbuilding, such as a shed, or even a garden storage box would keep it out of the rain, sun and protect the bin from frost.
The system involves anaerobic fermentation rather than the aerobic action of microorganism in conventional composting. It requires the addition of “Effective Microorganisms” (EM) which are a mixture of bacteria and yeasts to break down the food waste. These microorganisms will normally include yeasts, (Saccharomyces spp.), lactic acid producing bacteria (Lactobacillus spp.), and phototrophic bacteria (Rhodopseudomonas spp.)
The purchase of this bran will cost in the region of £40 - £50+ per year whereas most of the conventional food composters will not have any running costs.
Although often described as a composting procedure the bokashi bin is frequently used as a pre-composting process with the product being added to a regular compost bin or buried in the garden. The material can be buried in a hole but I feel that it is best to use the Trench composting method where a 30cm (1ft) deep trench is dug to bury the Bokashi product (often with the addition of uncooked kitchen waste) this can be left over winter to make a bean trench.
The commercially available Bokashi Bin normally consists of a plastic bin with carry handle, airtight lid and drainage tap. It has an inner drain tray to allow separation of the food scraps and liquid produced by the system and to prevent the solid material blocking the drainage tap. It will often come with a measuring scoop, a push tool and even a liquid drain cup. Some homemade systems do not include a drainage tap.
The microorganisms are introduced by spreading Bokashi bran thinly on the base of the bucket and over the food during the pickling process. Some systems recommend putting two or three spoonfuls of Bokashi bran into the bottom of the bucket before adding the initial layer of food waste This is most helpful when a system is being used that does not include drainage.. The food should be added in small pieces to form a layer about 3-4cm thick. Any large pieces should be cut to 3-4 cm to enable the microorganisms to ferment the food effectively and speed up the process. If possible, use fresh food. The Bokashi system will deal with food contaminated with white mould but green or black. Scatter about a measure or tablespoon of Bokashi bran the top of the layer of waste food and compress it by pressing down with the tool provided or a potato masher to remove air pockets. Cover with cardboard, plastic to exclude air and close the bin lid. Drain off the Bokashi juice every couple of days.
Repeat the layering process alternating food waste and bran as the waste becomes available, remembering to seal the bucket to exclude the air on every occasion seal until the bucket is full. Once full leave the Bokashi bin closed and undisturbed for two weeks or more, remembering to drain off the juice every other day.
Two Bin Systems
To work, effectively the system requires the use of two Bokashi bins. The bin in current use is normally kept in the kitchen so that plate scrapings and other food waste can be added directly to the bin. Once full, the bin is set aside for two weeks and the second bin brought into use.
During the fermenting process, the bin will produce a liquid known as ‘Bokashi tea’ or “Bokashi juice” which needs to be drained off every 2-3 days. This juice contains some of the Effective Microorganisms and can be used diluted 1:100 as a soil improver but it should not be poured directly onto the plants, as it is acidic. The concentrated tea can also be used as a drain cleaner or to reduce the odour from smelly drains. This may be advantageous where the house has a septic tank, as it may help maintain a healthy septic environment within the tank.
Being a fermented product the material in the Bokashi bin will smell different from compost having a sweet brewing, rather than an earthy, smell.
If the contents start producing an unpleasant odour, it could be due to contamination by blue or black fungi. This contamination may occur if the lid has not been fully closed, too little bran has been used, there has been inadequate compaction of the waste in the bin or not draining off the liquid.
If the bin is kept outdoors, it can also result from high temperature or direct sunlight.
It is quite normal for a white mould to grow on the fermenting material. The growth of a green mould is a sign that there might be a problem. This can indicate inadequate fermentation. During the early stages of green mould growth, the situation may be rectified by adding more Bokashi bran and the bin allowed time to recommence fermentation. However if the green mould is extensive the bin should be emptied. The mouldy waste can be bagged and sent to landfill
Bokashi Spray Activator
The Urban Composter sold by Original Organics is a 15L Bokashi suitable for those with smaller gardens or live in flats. It is designed to be used with a liquid spray activator, rather than the conventional dry bran. Raw and cooked food is added as for a conventional Bokashi bin but the contents are then sprayed with the activator rather than bran being added (you could choose to use bran if preferred). Boskashi liquid and solids are produced as with the more conventional bin.