DIY Soil Fertility – Part 2: Bokashi Composting System

Welcome to DIY Soil Fertility For Homesteads!

This post series covers the many ways you can build fertility, create soil, cycle nutrients and take responsibility for “waste” streams on your property – all with materials and substrates you are likely buying already or can be sourced for free or very low cast. These systems all integrate with one another to enable you to in-source your soil fertility inputs instead of relying upon centralized commodity supply chains. By employing these systems together in an integrated system you will improve nutrition (for soil and humans) and save dollars, while making living soil fertility enhancers better than anything you can buy at the store. The posts are written from our own experience and are geared towards the DIYer, though options are provided for ready-to-go purchased systems as well. Check the link tree below or at the bottom of the post to explore the rest of the series!

What Is Bokashi Composting?

Bokashi is an anaerobic method of fermenting organic wastes (i.e. pickling them) – as opposed to typical aerobic thermophilic composting that decomposes organic material. Bokashi systems in this sense are more a pre-composting method, as they do not yield finished soil, but instead microbially-rich fermented food wastes that are primed for incorporation directly into soil, thermophilic compost piles, or vermicompost systems (more on this below). Bokashi compost was developed at a commercial scale by Dr. Teruo Higa, a professor at the University of Ryukyus in Okinawa, Japan and founder of EMRO, a company that manufactures EM (effective microbe) products. Whether of not the word bokashi means “fermented organic matter” or not, it has become a household name in the West as means for producing exactly that.

Why Do Bokashi In Your Home?

Perhaps the most significant benefit of bokashi fermentation systems is that they are not as picky as other home composting systems as to what goes in them. In fact, bokashi systems can handle just about anything, save for perhaps gallons of used fry oil.

Bokashi fermentation buckets can accept all food wastes – even the types of the organic wastes that thermophilic pile and vermicompost systems typically cannot, such as;

• Bones
• Meat (cooked or raw)
• Some oil and fat (not too much)
• Dairy products
• Citrus rinds, alliums (onions, garlic etc.)

Bokashi is a means by which to process all of your own food scraps where you live and turn them into a nutrient rich soil amendment that your garden will love.

Bokashi buckets also take up a very small footprint, and emit no noxious smells due to their airtight lids (the fermentation environment needs to be kept anaerobic to function properly). Even when you open the buckets to add new material the smell is not offensive – it smells like something being pickled or fermented.

Bokashi buckets yield an acidic liquid as the fermentation process progresses. This liquid should be drained from the buckets every 1-2 days, and is an excellent plant food! The liquid needs to be diluted 1:100 before applying to your garden. It can also be drained down the sink – the microbes within it will help to clear sludge from pipes and keep drains clear.

Another significant benefit of bokashi composting systems is that the entirety of the nutrient content of the inputs is still present in the outputs. Because the fermentation process is anaerobic, there is no off-gassing of carbon or nitrogen as can happen in thermophilic piles. What little liquid is produced and drained during fermentation can be added to your garden as a plant food.

How To Do Bokashi Composting

Bokashi composting is very simple if you are purchasing pre-made inoculum. The process of making your own bokashi inoculum, while not difficult, does take time, and won’t fit into all lifestyles. The good news – a single bag of bokashi inoculum goes a long way, making purchasing pre-made inoculum quite affordable.

• Step 1: Sprinkle a small handful of inoculum into your bokashi bucket on top of the previous layer of food scraps. If starting a new bucket, sprinkle a small handful of inoculum at the bottom before adding your food scraps.
• Step 2: Add your fresh kitchen scraps and use a potato masher or something like it to compress the material. This will help exclude as much air as possible from the food scraps and ensure the dormant microbes on the inoculum get a good start. Continue adding and compressing material, always adding your handful of bokashi inoculum first so that it is buried by the fresh food scraps, until the bucket is full. Finish with a sprinkle of inoculum on top and then seal the lid.
• Step 3: Let your bokashi bucket sit and ferment for at least 14 days, ideally 21 if you can, and potentially longer if conditions are cold (indoor temps will help the process move quicker to completion). Bokashi pre-compost can also sit in the bucket for longer – it will not be harmed if you are gone on vacation or forget about it for a bit.
• Step 4: Time to use your bokashi!

How To Use Bokashi Pre-Compost

The pre-compost that comes out of your bokashi bucket after 14 – 21 days of fermentation can be used in a multitude of different ways.

• Bury It: Bokashi pre-compost is not the same thing as finished compost. It still has some breaking down to do. Perhaps the most common use of bokashi pre-compost is to bury it in your garden, covered by 4-6 inches of soil, and let the indigenous soil biota break it down into soil. This can be done via the trench method (dig a trench, sequentially fill and bury each batch of bokashi pre-compost as it finishes) if you have lots of open ground into which you will be planting later, or by digging individual holes wherever they fit into the garden. It is recommended to let indigenous soil biota work over the bokashi for ~ 2 weeks before planting, but we have planted young seedlings directly into the soil layer above buried bokashi and they have done incredibly well. As long as young plant roots aren’t put into direct contact with the acidic pre-compost immediately it will break down and neutralize by the time the roots reach it.

• Compost It: Bokashi pre-compost makes an excellent addition to thermophilic compost piles, and can be an excellent way to jump start them should they be a bit cold. Once passed through the thermophilic composting process the bokashi ferments can be used to top dress garden beds just like any other compost mix.
• Feed It To Your Worms: Bokashi pre-compost can be added to vermicompost systems, however this should be done methodically and with regular observation. Bokashi compost, once it is fermented, is quite acidic, with a pH typically in the 3-4 range. Worms don’t generally like acidic foods. However, they will often enjoy bokashi pre-compost when it has had a chance to sit and be exposed to the air for a few days (who knew!?). We feed some of our bokashi to our worms, and just add it on one end of the flow-through vermicomposter, to allow them time to acclimate and/or for the bokashi to de-acidify somewhat. Over time continual additions of bokashi pre-compost can acidify a worm bin, and additions of lime may be required to ensure the pH stays friendly to your worms. If and when we add bokashi pre-compost to our worm bins, we also add a healthy serving of wetted cardboard to help absorb some of the acidic leachate.

• Store It: Can’t use your bokashi right now? No problem, the fermented material stores well – it can simply be left in the bucket until you are ready to use it. The microbes will simply go dormant once they have fermented all of the available substrate.

Do-It-Yourself Bokashi Composting

Purchasing bokashi buckets can be rather expensive, especially if you have a household of 4 or more people – for which you’ll probably need at minimum three buckets to keep in rotation (one filling, two fermenting). Purchasing bokashi inoculum also represents an ongoing cost of this style of composting that some may wish to avoid. The good news is that you can make your own DIY bokashi buckets for 75% less than purchasing the pre-made version, and you can make your own bokashi bran on the cheap if you’re willing to put in a little extra microbe-tending.

We made our own bokashi buckets using (2) 5 gallon buckets, (1) fitted lid, and (1) bulkhead fitting and drain spout. They work the same as the pre-made buckets, though the drainage is not quite as complete and requires tipping the bucket to get more of the liquid out. One bucket has small (3/16″) holes drilled in the bottom at approximately 1 – 1.5″ spacing, while the other has a bulkhead and drainage spout mounted as low as possible on the bucket side wall. The bucket with holes drilled in the bottom is where the food scraps will be deposited, and will drain into the lower bucket with the drainage spout. Nesting the food scrap bucket inside the drainage bucket keeps the system air tight. It works, but not as well as the buckets with pre-cast drain units in the bottom, and so you’ll get more liquid build up, which gets stinky.

Pre-Made Systems For Starting Immediately

If you want to purchase a bokashi bucket system to get started right away with a system you know will work, there are many starter kits available – like the Bokashi Compost Start Kit from Bokashi Living (we use this in rotation with out DIY buckets). We have also used the Sunwood Life Bokashi system and the SCD Probiotics Bokashi system (both the same as Bokashi Living) – a way to get started with only a single bokashi bucket if you want to try it out without buying too much at the outset.