Despite its name, Bokashi composting is a fermentation process for handling kitchen scraps right in the home. It is fairly easy to do and produces few odors. The majority of the material ends up as fermented kitchen scraps and some is drained out the bottom as a brown liquid, commonly called Bokashi tea or Bokashi leachate. Advocates of this process claim that the Bokashi tea is a good fertilizer, full of all the nutrients your plants need.
In my previous discussion about Bokashi, I speculated that the tea contained few nutrients. At the time I found no chemical analysis of Bokashi tea, not even from proponents of the process. One of my readers has now found such a study and I will have a close look at the data in this post.
What is Bokashi Composting?
The process is called Bokashi composting, but in reality it is not a composting process. As discussed in my previous post, this is a fermentation process. It pickles the food scraps and the end product is called Bokashi ferment which is then added to a compost pile, or incorporated into soil to start the real composting process.
The excess water and juice from the food scraps migrates to the bottom of the Bokashi pail, and are drained away to prevent the fermenting material from getting too wet. This liquid is called Bokashi tea, or Bokashi leachate.
Chemical Analysis of Bokashi Tea
In this study, kitchen scraps were obtained from several places including a home, and I am going to use that data since it is more representative of the material a gardener would process. The collected material was then fermented in a lab location so they could control the environment. The table above shows nutrient levels in pure Bokashi tea (concentrate) and the diluted form (middle column) which is 2% of the concentrate. The 2% value is considered high by the researchers, whereas 1% is considered low.
To compare this to normal fertilizer values, I have added the values for the MSU fertilizer which is used for growing a wide range of plants including orchids.
Note that the above table shows the macronutrients in mg/l and the micronutrients in ug/l. The values for the MSU fertilizer have been converted to element mass numbers to match the ones reported in the research (ie P values instead of P2O5).
Nitrogen levels in Bokashi tea are very low. Phosphorus and potassium are on the high side.
The level of several micronutrients are also very low.
Levels of Sodium and Chloride
In addition to the plant nutrients reported above, the Bokashi tea also had high levels of sodium (1200 mg/l) and chloride (4300 mg/l). Once diluted to the 2% level used in the above table, the leachate will have a sodium value of 24, with 50 being toxic to plants. The chloride is at 85 mg/l and a value of 70 is considered toxic.
Much of the sodium chloride would be from salt added during cooking, or salt added as a preservative in commercial food. People using Bokashi leachate on plants should be careful which food they process.
Growing Plants With Bokashi Tea
The study also tried growing pak choi in a number of different medias using both Bokashi tea and standard fertilizer.
Plant growth using Bokashi tea was much slower than control plants, in both sand and peat substrates. It is assumed that this is largely due to the very low nitrogen levels.
“The low concentration of inorganic nitrogen in the leachates can be assumed to be due to denitrification processes taking place during the fermentation, as the food waste was kept anaerobically in air-tight containers, thereby promoting denitrifying bacteria. ”
Should You Use Bokashi Tea as a Fertilizer?
Bokashi tea could be used as a fertilizer if additional nitrogen is added. Without the added nitrogen, it is a poor fertilizer at best and at worst, the high sodium chloride could be toxic to plants.
I would not recommend it for use on potted plants. Add it to the garden where additional nitrogen might be available, and where excess sodium is easily washed away.
It should be diluted to at least 1% to ensure the sodium chloride levels are not toxic.
What test kid did you use, I ‘d like to order one for my bokashi tea. I usually add mostly fruit and veggie scraps but not a lot of meat or fish. I will be careful with salty foods now.
Since you will get what you put into the bokashi, my result might be different from restaurant bokashi tea.
Most likely restaurants use lots of salty food, and food scraps for the test differed a lot depending on the restaurant. Some or most had barely greens, just one listed veggies ….but how much veggies ? That is why summing up the tests makes no sense to me.
Separately summing up for each restaurant might be better.
And giving up the bokashi because of that…why??
the fermented food doesn’t stink and it speeds up composting. It kills wheat
One said that potassium is so good, I will appreciate my bokashi tea as an “almost – fertilizer”!
you’ll have to let the researchers know.
Bokashi tea generally lacks in nitrate, so no good for fertilizing
This is very surprising to me, but good to know for further research.
Assuming all is a myth that tea is actually not good for fertilizing , this test result also shows tons of nutrients in bokashi tea.
Salty? The table doesn’t show sodium content
For me , Bokashi is worth doing ,the tea is just a bye product
I tried all of these things:
-all food can be composted and saved from the landfill, meat, cheese, cooked,
-bury fermented scraps 20” deep and after 2-4 weeks it is gone and there are tons of earthworms
-tea kills wheat without killing bees or grass
As much as myths bother me, there is also a few things I dont like about this test sheet in your article.
Usually a test shows the name of the institution who ran it, reflects criteria on how it was run and the number of tests done. I don’t see this.I also don’t see in the table showing the sodium content?
Also it might be valuable data to mention what was added to the Bokashi. Since each Bokashi can be very different that might be the reason why there are few if any chemical analysis out. And we need more , definitely.
But assuming there was enough nitrogen or greens added, what could have destroyed the nitrogen?
Such a low number of nitrogen is puzzling to me.
Let’s assume many tests were run with different teas from different Bokashi batches. –
Maybe lack of greens added to Bokashi bin, too much salty food, too much paper, tea was not fresh , what test was chosen, a data mistake, was nitrate content tested multiple times, etc.
Anyway the tea is still good as plant food if I read the table correctly
Thank you for this article, made me think a lot!
All of the data you are asking about is in the reference provided.
There is no “test sheet” in my article – it is a summary table.
Isn’t it even a good fertilizer for already grown vegetable plants which need P and K?
Thanks,
Bokashi is mostly undecomposed plant material – as good as other compost.
Hi guys, lots of interesting yet conflicting info here. What is the bottom line – yes or no to bokashi? I am a moringa farmer and certified organic so I do not use anything synthetic. I am looking for new ways to improve my crop and am considering bokashi. It will also process foods that attract rats to my traditional compost heap. The best method to date of producing a nutritive tea has been worm tea but I need a larger quantity than my worms produce. Who can give me some guidance?
I have not try bokashi tea. I recently try fish fertilizer using EM (no or very little smell) which studied said high in Nitrogen content and calcium . May be it a great combination of bokashi tea and fish fertilizer?.
Thank you for the article and advice
Your right and I agree Bokashi is not a good fertilizer if applied in the same fashion as synthetic fertilizers. Bokashi in my understanding is more of a soil additive which increases fertility and yield by expanding biodiversity in the soil.
I get your point of dead vs alive bokashi. Yet wouldn’t simple deduction say that if the bokashi were alive when entering the soil any benefits it had would at minimum have to multiply to some degree as it continued its lifecycle and the longer it was alive in the soil the greater the benefit it would provide?
I understand your scientific method way of analyzing the information which is available, but allot of your debunks rely on the assumptions that the tests that have been performed took into account the actual methods and processes people are using bokashi for. Then you turn around and defend your conclusion by saying no other information is available so bokashi is therefore a poor fertilizer.
For example you quote that Bokashi tea was much slower than control plants, in both sand and peat substrate. So all we can truly take from that is that bokashi isn’t effective on sand and peat substrate(sterile environments void of organic matter)…. Studies Yet to be done would include its effectiveness on all the other substrates known to mankind….
So your title should in essence be “Is bokashi tea/leachate effective when used in the same manner as synthetic fertilizer?”
Compare an orange + the equivalent of the bokashi bran added directly to soil, and an orange first fermented with Bokashi. The same organic matter and nutrients are both added to the soil. Why would one produce better results?
If you think that is still true – find a study to support your claim.
Ok so your saying the bokashi bran and and orange put directly into the soil would produce the same chemicals and compounds as the bokashi tea/leachate processes?
Once decomposition is complete – Correct – matter can not be created.
Bokashi would add different microbes – but to date there is no evidence these make any difference.
During decomposition you would have different intermediary chemicals – but there seems to be no evidence these do anything different either.
Your post clearly says that you grew Pak Choi in sand and peat and the added nothing but bikoshi tea . This is useless information and I could have saved you some time .
Microbes need nutrients to be effective
The post does not say that. I am reporting on other peoples published research.
You may want to reread the post Ralph. Robert didn’t grow the Pak choi. There is even a link to the research paper where the Pak choi was grown.
Teas are not fertilizers Robert , in order for teas to work properly they need nutrients to eat ( not synthetic) and be made available to plants . Adding microbes to a dead soil like sterile peat and sand as you did in your test is like peeing on a forest fire and it’s not going to do anything. I suggest you try your test again with a living soil instead of whatever you got from Walmart and you will see a big difference.
“Teas are not fertilizers Robert” – but so far the science shows that teas are only fertilizer – the microbes add no value.
“Adding microbes to a dead soil like sterile peat and sand as you did in your test” – not sure what you are talking about – I did not do such a test, nor have I done any test with microbes.
The test your asking for doesn’t make any sense as dead microbes are bio available nutrients for plants .
How does killing them solve this debate?
This is standard science. You want to design the control so that it proves the hypothesis you are trying to confirm. In my experiment, the only difference between the two test samples, is the living vs dead organisms. Total nutrient content is identical.
If I am correct, and the living organisms die once added to soil, then you will see no difference. If you are correct, and the organisms live, and grow, and have an effect on the soil or plants other than just adding nutrients, then the plants treated with live organisms will grow better.
I have seen hundreds of studies that compare teas of various kinds to water. That is a useless test since we know that adding more nutrients grows plants. If you want to prove that the live organisms have an effect, you have to compare live ones to dead ones.