What is Bokashi Composting?
What is Bokashi composting? The rough translation is ‘the fermentation of organic materials’, which is pretty broad. With this broad definition of Bokashi we can liken it to a basic fermentation recipe. So in that way, you can think of this as a guide to fermentation. I like the Bokashi buzzword, it sounds cool, but don’t feel like you’re limited to fermenting kitchen scraps in your “Bokashi Bin” (aka fermentation bucket – sounds way less cool).
It’s important to note – Bokashi composting doesn’t break things down the way traditional aerobic composting does. You won’t get a pile of dirt from your kitchen scraps, fish, bones or whatever you’re composting this way. You will simply have the same material, looking a little more monochrome, more easily broken/separated/smushed when you squeeze it, and smelling sour. BUT, this material, in the next stage of decomposition, will break down much faster and more completely than it would otherwise.
Why Bokashi Composting??
So Bokashi composting, under the broad definition above, is far from just pre-composting kitchen scraps bound for the traditional compost heap. It is a valuable tool we can use to boost the decomposition rate or digestibility of a nutrient source. Just like in the anaerobic compost tea, we aren’t worried about overloading the system with nutrients. You don’t need it to heat up, so you don’t have to monitor the ingredients to get just the right balance of greens and browns. It won’t heat up like a traditional compost pile, so it won’t get too hot if you put in all green nutrients.
Just like comparing aerobic vs anaerobic compost teas, we can compare bokashi composting to traditional composting. Aerobic composting produces a wide variety of beneficial aerobic microbes which break down a limited amount of nutrients into plant available forms. In bokashi, a little more limited group of beneficial anaerobes break down an unlimited amount of nutrients into more plant available forms. The breakdown process doesn’t go as far as traditional composting, but it still makes a much more bioavailable nutrient source for whatever your need – plants, animals or people.
So, unlimited nutrients. In fact depending on the need we will use only nutrients in the system. In this way you can break down a ton of material safely and without smell. You can’t just put your kitchen scraps in the compost heap every day. You will likely end up with a wet, sloppy, stinky mess that will harm the garden rather than help. So instead, you’ll use bokashi to break down the material scentlessly and safely before adding it to the garden or compost bin. If you want to make your animal feed much more effective, increase the growth rate of your animals, you’ll use bokashi to pre-digest their feed. Or maybe a batch of animal feed got wet and will spoil or has already started to spoil. Bokashi! A ton of green waste and no brown waste to balance it out? Bokashi! After fermenting, you can add the waste to the garden where it will quickly break down and feed the soil. There are a myriad applications of this valuable technique.
Basic Principles of Bokashi
As mentioned above, you can ferment anything organic – food, paper, bones, sticks, coffee grounds, moss, leaves, animal waste, bird feathers, etc etc. It just involves adding an energy source (sugar most commonly), the right microbes, proper moisture level, and keeping the system anaerobic (no oxygen).
The simple energy source should be simple carbohydrates – sugar, syrup, molasses, honey, jaggery, etc. The generally accepted best source is molasses, because of all the vitamins and minerals it contains. In any case, the simple carbohydrate source is the basic feed of the anaerobic bacteria that you’ll use to ferment the solids in your system. You can use up to 1/3rd part sugar in terms of solids. For example, you might have 30kg of solids to ferment, you would add 10kg sugar max. You can use less sugar, and the fermentation will not proceed as far along since there is less food source. You can also diversify the feeds by adding other energy sources – fruits which contain sugar, etc. My personal guideline with sugar is – the more biologically active the ingredients, the more sugar to be used. The abundance of food helps beneficial fermentation bacteria dominate. For example I would add more sugar when fermenting bird feathers or fish than I would coffee grounds or fresh cut leaves. The other guideline I follow is stated above – the more sugar you add, the ‘farther’ your system will ferment and the ‘stronger’ it will be – the bacteria convert sugar to alcohols and acids. So for example when making animal feed Bokashi I add less sugar than when making compost Bokashi.
Just as in aerobic composting, in Bokashi microbes are the foundation and good quality Bokashi hinges on having the correct microbes. Lactobacillus bacteria are the main workers here, but also other anaerobes like Actinomyces, Streptococcus, Staphylococcus and more. To make sure these beneficial microbes dominate, we’ll inoculate our Bokashi with a microbial inoculant that is chalk full of them. That way they get a head start on other bacteria. These beneficial anaerobes produce enzymes and other byproducts like organic acids that hinder the growth of competing bacteria – that’s why fermentation is a food preservation technique – pathogens can’t grow! It’s still possible to Bokashi without the microbial inoculant, but there is a much greater risk of the batch going “bad” – the wrong bacteria thriving – we don’t recommend it. If you don’t have the microbial inoculant I’d advise adding more sugar to your Bokashi. You can monitor your Bokashi by smell – it should smell faintly alcoholic/vinegar/sour but not in a foul way.
Bacteria don’t thrive in dry conditions – often they don’t die either, they form cysts/endospores/etc and wait out the poor environmental conditions. We want active bacteria not sleeping bacteria – so we’ll make sure there is enough moisture to keep them alert and mobile. For me that is at least 30% moisture. You can have more no problem, but I wouldn’t recommend less than 30% moisture. I think they are just more efficient in a moist environment. Maybe someone can pitch in here on the lower limit of moisture level, this is the arbitrary limit I work with. My animal feed Bokashi is normally around 45% moisture level. Enough that you squeeze it and it clumps firmly together in a ball but doesn’t drip. Keep in mind this is an anaerobic technique, so there is no upper limit to the moisture level. The moisture level you use depends on your purposes, really. For fermenting animal feed for example, normally you start with a very dry feed and just wet it enough for the microbes to work – no need to make animal feed soup. For kitchen waste bokashi, you don’t really worry about the moisture level, but normally you add a drain for the simple fact you can drain off the nutrient rich bokashi leachate as it forms.
Lastly, oxygen level. This technique, Bokashi, is an anaerobic process so it has to be oxygen free. We’ll exclude oxygen by keeping the system sealed – in a bucket with lid, sealed plastic bag, etc. It is best to use a bucket with lid though so that you can pack the material down and it won’t change shape, and also won’t be disturbed during fermentation. That is a big factor – during fermentation keep the Bokashi system as static and undisturbed as possible – minimize the gas exchange in the system. This helps ensure you have a successful fermentation – introducing oxygen and thereby aerobic bacteria is one of the easiest ways to get a bad Bokashi – you will know when you finish the fermentation and it doesn’t smell right, smells foul. Remember a good Bokashi should smell, after about a month or so, faintly alcohol/vinegar/sour but not foul or putrid.
Now we’ve covered the basic principles of Bokashi composting. Keeping these principles in mind, you can ferment any organic solid to break it down into more easily digested/degraded/composted material ready for human/animal/plant/microbe consumption.
There are all kinds of examples of bokashi out there. Commonly it is done at home in the kitchen below the sink – kitchen scraps going into a bokashi bin, which gets emptied into the compost pile when it fills up. My mom does this at home. Funny story – the first time she drained the bokashi leachate for use with the houseplants, she mixed about 1cup per gallon. Only a couple of the plants died but they all got burned. Haha, be careful with that stuff it’s strong!
How it’s done: normally this bokashi is made in layers. Start with a layer of ‘bokashi bran’ which is just bokashi itself – fermented wheat bran normally. Make the bokashi bran by mixing water, sugar, and a microbial inoculant like our lacto serum with the carbon rich growth medium. The growth medium is normally bran (wheat, rice, barley, rye, etc), but you can use any carbon rich source – sawdust, newspaper, groundnut cake, wood chips, etc. Ferment the bran at least 3 weeks prior to use. Once you have the bran ready, start with a layer of that. This establishes the microbes needed for proper bokashi making. After the first layer of bran, add the first layer of kitchen scraps (anything goes with the kitchen scraps – meat and dairy included – fermentation kills pathogenic bacteria). Alternate layers of bokashi bran and kitchen scraps from then on. When the bucket is full, empty it into the compost pile or bury a few inches deep directly in the garden.
You can use bokashi for much more than just the garden. An example of that is animal feed bokashi. I practice this at home. The dog and the roaches get the same food. It is a mixture of dog food and some other things I have around that are excellent nutrition sources. These ingredients are mixed and then fermented for 6 weeks. This bokashi is an awesome food – both dog and roaches love it! In the case of the roaches it is a filler when no kitchen scraps are available, it’s a nice treat for them haha.
How it’s done: Take your animal feed, whatever it may be – seeds and grains for rodents and chickens, pellets for your pigs, dog or cat food, etc. Add the water, sugar and microbes like lactobacillus and BIM until the feed is sufficiently moist (30%+). Then add the feed to a sealable container like a 5 gallon bucket or 50 gallon drum. Pack it as you go to remove as much air as possible. Leave for at least 4 weeks to ferment, then feed to animals. Keep it sealed when not using, to maintain anaerobic conditions, or dry it out away from sunlight to keep longer term. You can use this bokashi as the bokashi bran for your kitchen scraps – it is a great microbe source to keep your kitchen scraps bokashi fermenting properly.
Bokashi is a valuable tool in the natural farmer’s toolkit. It goes far beyond simply composting kitchen scraps. It has applications all over the farm, when other forms of composting are unsuitable or when conditions don’t permit. It allows you to safely compost large quantities of wet, nutrient rich material that would otherwise spoil. Keep this technique in mind and have fun anaerobically composting around your farm and garden!