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.
Robert
Korean natural farming has been around for 100s of years is still practiced today all over Asia and more recently in North America.
Bikoshi Tea consists of facultative anaerobes the result from the fermentation process. These microbes are very effective in the soil at mining nutrients and there is more studies on this then you have had birthdays .( check out Dr Hitto from Embro Japan ) Facultative anaerobes can survive with or without oxygen and makes them deliverable . This means you can put them in an air tight bottle with a complex carbohydrate and they can survive for up to 2 years , unlike compost teas that will be dead in 72 hours and are aerobes
I have many lab tests and university studies that prove these claims I just can’t seem to find a way to upload them on this comment section but if you give me your personal email I can send you some . There is also independent reviews on our website acterratech.com
Do a germination test on some radish seeds and see for yourself .
1) take some bikoshi tea and dilute it 100:1
2) spray it on your paper towel and do your baggy test
3) you should see a noticeable difference in biomass over control after about 3 days ,
The more diversity in your food waste the better
Ralph
Those are all the claims being made, but is there evidence?
Show me one published study that takes the bokashi tea, splits it in two, and sterilizes one of these samples to kill the organisms. Then uses this tea in a field study to show that the one with living organisms makes the plants grow better.
That would prove that it is the living organisms and not the nutrients in the tea that are making the effect.
You can add a link right in the comment.
Great article, as always.
If you think about it, most of these myths are similar to people thinking Pink Himalayan salt has to be healthier than regular table salt because if comes from those mountains. Just like the nutrients (e.g., “Nitrogen”) I get from my garbage scraps has to be better/safer/different than any synthetic / organic-synthetic nutrient (e.g., NO3-; NH4⁺).
Thanks for a little science in my online diet!
The nutrient content in bikoshi tea compared to synthetic fertilizers is not important. Bikoshi tea is loaded with Beneficial microbes with the most being lactobacillus and should be considered a bio stimulant not a fertilizer. The CFU counts are about 20 times higher then compost teas that are all but useless and quickly consumed by the indigenous microbes in the soil . Bikoshi tea is loaded with nitrogen fixing bacteria and fermenting fungi and yeasts . The only thing that is correct about this article is for best results you should dilute down to 1 percent . Do not use with synthetic N fertilizers.
Ralph Lett
1) Where is the data to show these high counts?
2) Where is the data that shows adding microbes to soil provides any benefit – the science does not show this. The references in my post even discuss this point.
3) “Bikoshi tea is loaded with nitrogen fixing bacteria” – where is the evidence for this? If this were really true, and these bacteria were active in the tea – would you not expect high levels of nitrogen? You have the opposite.
4) The results of the test clearly show that plants do not grow well with Bokashi tea. If the microbes were there and doing a good job, plants should be able to grow in the tea.
Robert, You commented “Add it to the garden where additional nitrogen might be available, and where excess sodium is easily washed away.” If the sodium is easily washed away, wouldn’t other nutrition’s also be easily washed away. And if that is the case, it would seem to me that it’s kind of pointless using the tea in the first place.
The rate at which nutrients are washed away depends on the nutrients. Sodium is very soluble, compared to something like calcium or phosphate.
Surely the composition will vary a lot depending on what gets included in the compost? The Bokashi process can’t create minerals. If I add some left-over raw liver to the compost, for example, it will have a very different composition to all-vegetable matter. I imagine this will apply to the leachate just as much as to the compost itself.
But the true Bokashi believers claim things like “Bokashi tea is full of all of the beneficial bokashi microbes that help to unlock the nutrients and minerals in your soil”. I recall you dismissed claims about the benefits of the microbes as unscientific nonsense in your earlier post.
The values will vary depending on the scraps. The referenced study also has values for schools and restaurants. But all of them had low nitrogen, and high P and K.
The study also talks about other work on the value of EM microbes and concludes they add little to mixture.
This has surely answered some of my basic issues with this method of breaking down household scraps.
You can easily make your own bins which I presume you mean by ‘apparatus’.
If this is a reply to my comment – there’d be no incentive to lie about the nutritional benefits of the liquid drained off from the fermentation if there wasn’t some potential commercial benefit to the originator of the myth, so one has to assume that’s where this garden myth comes from.
So what about the solid fermented material left over? Can you add it to your compost? The reason I am asking is I have heard Bokashi can break down things not normally used in compost like dairy, meat or even bones. I think it would be great if I could use these items rather than just throwing them away.
Click on the links to my other posts for that kind of information.
Thank you for good advice!
So I guess the idea is to sell the apparatus in which the fermentation occurs, without cocern for whether the plants in the gardens benefit?