2021-09-13

Bokashi composting, hands on guide

[WIKIPEDIA] Bokashi is a process that converts food waste and similar organic matter into a soil amendment which adds nutrients and improves soil texture. It differs from traditional composting methods in several respects. The most important are:
  • The input matter is fermented by specialist bacteria, not decomposed.
  • The fermented matter is fed directly to field or garden soil, without requiring further time to mature.
  • As a result, virtually all input carbon, energy and nutrients enter the soil food web, having been neither emitted in greenhouse gases and heat nor leached out.
Put it simply, you are preparing food for worms, not the soil itself so this method is suitable for people with gardens.
PROS CONS
No hustle. No soil produced.
No excessive CO2 production. Pungent smell.
Easy to get right.
Does not attract mice/rats/harmful insects.


Chemistry


Please see this Wikipedia article for details.


The HOW


You need to harvest and grow lactobacillus. For this you can basically use any organic food produce like cabbage or rice. I will give receipt for rice (any rice but paraboiled should do):
  • 0.5l of water (non-chlorinated)
  • 70-80g of rice (any except paraboiled, the more the better, rice can be reused for cooking)
  • 15g of sugar (any)
  • 5g of salt (any)

GOTCHA: If you do not have access to non-chlorinated water, please boil tap water and leave it for a day or two before using it.
There is no point in using any special rice, sugar or salt. This is urban myth. I'm guessing paraboiled rice is not fit for this being that most of the useful organisms will die during pre-boiling.
Quantities scale linearly so to make larger batch, just multiply with same number.
When weighing ingridients, it is not important to be exactly precise so, say, rice can be more. But, it is better to have 1g of sugar more than 1g of salt. Meaning, rice 85g, sugar 16g, salt 4g is perfectly good receipt.

Equipment:
  • Plastic bottle with loose cap or fermentor cap such as this one. It is important that a cap is loose because of CO2 buildup while lactobacteria processes sugar to grow.
  • Funnel with sieve to prevent rice grains getting into solution. Impurities will clog nozzle.
  • ph strips covering acidic spectrum (say 1-5).
  • A bowl to mix rice in.
  • Spray bottle.
  • Bokashi bin.
The process:
  • Pour dechlorinated water and rice into bowl. Grind rice grains against each other with your hands until the water is cloudy white. The whiter the better. This should not take more than couple of minutes.
  • Pour half of the mixture into the bottle using funnel.
  • Add salt and sugar into bottle.
  • Pour the rest of the mixture into bottle and close it.
  • Shake the bottle vigorously and place into dark, warm corner.
  • Rinse the bowl and funnel under running tap water.
When it occurs to you, shake the bottle and, if needed, release CO2 from it. This can be once a day or so. Lactobacillus is photo/aerophobic but this just means it will grow slower when aerated/insolated not die altogether.
After 2-3 days, depending on how warm your corner is, you can start checking if there is enough lactobacillus in your mixture. Open the bottle and place pH strip into it for couple of seconds. You are looking for pH value of 4 and less (I usually wait for 3). This is becaus of two things; botulism bacteria naturally occuring in rice die off at about 4.5 and values of 3 and lower indicate "runaway" reaction mening we have almost pure lactobacteria culture. The mixture smells sour.
When the mixture is prepared, pour into spray-bottle, it is ready to use.

Composting:
Open the bin, spray some of the liquid on the sides, put the food leftovers in it, press hard, close. Repeat until bin is full. You can add a spoon of sugar occasionally.
Once the bin is full, leave for some 2 weeks to ferment. Regardless of urban myths, this is not mandatory as the fermentation process will continue even after you bury the contents into ground.
After the maturation, please bury the contents into a hole in earth or dispose into composter. Personally, I have 2 boxes made of thick wire so they have contact with ground attracting worms. Make sure the mixture in composter is always kept wet. This is good for worms and keeps mice away.
Once the bin is empty, you can wash it. I use rain water to preserve what remained of lactobacteria but tap water is also fine. Drain fully for a day or so especially if you washed it with tap water.
The soil is ready to be used when there are no discernible pieces of food in it any more. Take this with grain of salt, of course you can see some pieces of food, depending on type of food and how big the pieces were. This does not make soil unusable in any way.

Finer points of the process and what to watch for:


It is important to press the mixture in the bin firmly to get rid of excess air. This will also crush, for example, eggshells and similar. The pieces should be small enough not to trap air in them. In normal language; I chop orange/lemon peels into several pieces instead of putting citrus dome into bin. On the other hand, cabbage, salad, fish remains etc. I do not cut at all.
It is OK to have pieces of raw flesh in the bin. Once fermented, it will not attract rats and such.
Do not make excessive amount of bokashi mixture. After processing the sugar in it, bacteria will start to die. Generally, if I have mixture for more than 10 days, I add a few grams of sugar directly to spray bottle and shake.
You can put anything but the bones and nut shells into the bin. Lactobacteria will eat through even fish bones and egg shells.
If you ever wondered why the pipe on the bin, it is because liquid is produced during fermentation. You need to relieve this liquid from the bin so it does not soak the contents. Mind you, the smell is pungent! The liquid obtained can be diluted and used as fertilizer or simply poured into pipes, earth, compost bin, septic tank and so on. The warmer the place for the bin, the more liquid is produced! Bacteria count drops by half with each degree Celsius drop in temperature.
GOTCHA:
Harmful mold can develop in the bin if you fail to drain it! If you open the lid and see black mold on top, take the bin somewhere far and pour the contents over the ground. Do not bury it as we want the elements to do the desinfection for us. This goes for the bin too. On the other hand, if you see webby-white mold in the bin, that's perfectly fine, even desirable.
Earth worms are not very active below 20C so it will take more time for them to process the food in winter.

The RESULT

Dense, black soil-like matter teaming with worms and other living things. It can significantly improve soil quality in your garden, flower pots etc.