Bokashi Composting: Step-by-Step Guide

Woman harvesting environmentally friendly fertilizer from bio waste using diy bokashi.

Guido Meith / Getty Images

Overview
  • Working Time: 2 - 4 hours
  • Total Time: 2 - 3 weeks
  • Yield: 1 gallon of bokashi tea
  • Skill Level: Intermediate
  • Estimated Cost: $100-150

Bokashi composting is a bit different from other methods in that it's actually a fermentation system. The end result is also different from the compost you'd get from a hot, cold, or worm (vermicompost) system. Instead of a dark brown soil-like material, you end up with a nutrient-rich liquid called "bokashi tea."

One of the biggest differences between bokashi composting, or fermentation, and other types of composting is that it works anaerobically (without oxygen). In hot, cold, and vermicomposting, oxygen is incredibly important to ensure proper breakdown of the material. This difference means bokashi composting also produces less CO2 than other types of composting, a distinct advantage.

And because this is a fermentation process, you can put more types of materials in your composting bin. In addition to the veggie and fruit scraps, eggshells, tea, and coffee grounds, you can also add fat, dairy, meat, and even bones to a bokashi system. It also works much faster than any other type of composting, with the whole process taking 4-6 weeks.

Since bokashi is a closed system, you will need a specially designed bucket that collects the liquid fertilizer at the bottom, separate from the solid materials. These systems usually have a spigot so you can drain the bokashi tea.

One disadvantage to the bokashi system is that there is material left over after it has been fermented and the tea drained from your scraps. This material would then need to be added to a regular hot or cold compost or otherwise disposed of to complete the degradation process. You also won't be able to compost large amounts of yard waste using a bokashi system—it's for food waste only.

Why Composting Is Good for the Planet

Going through the trouble of bokashi composting has quite a few benefits beyond creating a nutrient-rich plant food from your food scraps.

Since 30% of garbage is made up of food scraps and yard waste, composting saves landfill space and reduces the greenhouse gas methane (when food waste breaks down in the oxygen-free environment of a typical garbage dump, methane is produced).

While the bokashi system is also anaerobic, the specific chemistry of homolactic fermentation means that methane isn't produced at all.

What Can Be Bokashi Composted and What Shouldn't Be?

Bokashi composting—because it's actually reliant on fermentation— can include more types of food-waste material than composting systems you might be familiar with. In addition to the typical fruit and veggie scraps, you can throw bones, meat, fat, and dairy products into the bokashi bucket.

However, because it's a smaller system that's designed for food waste only, you can't compost large amounts of yard waste in a bokashi system as you would with cold or hot composting. It's actually important to have a high amount of carbohydrates for a bokashi system to work well, so yard waste would also knock off the balance of carbs vs. other materials that the bacteria like to eat.

While you can include some materials that would be excluded from regular home composting, there are a few things you can't bokashi compost. Small amounts of oil are OK, but don't dump that expired bottle of olive oil (or any other oil) in there. Liquid in general isn't great for the bokashi system, so don't dump that quarter-cup of tea in there either.

Avoid adding any produce or meat that's already very rotten. You should also avoid adding any waste that has green or black mold on it (white or yellow molds, which are common on bread and cheese, are OK). Rotten food and dark molds have organisms that could actually act against the bacteria that are doing the hard work in a bokashi system.

What You Can Bokashi Compost

  • Fruits and veggies, cooked or raw
  • Eggshells
  • Coffee grounds and looseleaf tea
  • Cooked food and leftovers (don't put hot food in, wait until it's room temp or colder)
  • Beans, lentils, hummus, bean dips
  • Nuts and seeds
  • Plant clippings
  • Meat, fish, and bones of those animals
  • Dairy products or food with dairy in it
  • Fermented and preserved foods
  • Oyster, clam, and shrimp shells

What You'll Need

Equipment

  • 1 Bokashi bin
  • 10 jars for bokashi tea storage (half-gallon size)

Ingredients

  • 5 gallons of food waste
  • 2 pounds bokashi bran

Instructions

Bokashi composting requires a specially designed bucket that you will likely need to buy. Though there are DIY versions out there, you'd need to be fairly handy to make one. The bokashi bucket should keep your food scraps elevated above your liquid and have a way to easily drain the tea via a spigot at the bottom. The whole thing needs to be totally self-contained and airtight so it won't smell or attract insects.

Besides the bucket, the other important component in this system is the inoculant, usually a combination of bran, molasses, and effective micro-organisms (EM) made up of specialist bacteria (Lactobacilli) and yeasts (Saccharomyces) needed for the fermentation process. These bokashi bran bacteria convert some of the carbohydrates in your scraps to lactic acid through a homolactic fermentation process. This inoculant can be found online as bokashi bran.

  1. Prepare Your Bokashi Bin

    Buy or make your bokashi bin. Some people use two bins so that one can be fermenting while the other one is being filled. Each bin will hold about 5 gallons and an average household will take about two weeks to fill it.

    Then, find the perfect spot for your bins. Since they do not smell, many people keep them indoors. If you want to place your bins outside, make sure they are in a shady spot. A warm-enough garage could also be a good option. Keep in mind that your bokashi bin can't be kept outside when temperatures drop below zero because that will kill the bacteria.

    After the fermentation process is done, you'll have material left over that you'll be able to compost or work directly into your garden soil.

  2. Order Bokashi Bran

    Look for bokashi bran, a dry product that comes in bags. You will need to store it at room temperature and avoid any possibility of it freezing.

  3. Load Up Your Bin

    Start adding food scraps to your bin. Consider chopping them up into 2-inch or smaller pieces, as this will help the chemical process move more quickly. You can add the food scraps as you produce them. When you open the bin, it will smell mostly like pickles or sauerkraut.

  4. Add Bokashi Bran

    Add one or two tablespoons of bokashi bran for every inch of material you add to your bin. Err on the side of adding too much (you can never add too much bran, though you can definitely add too little). Smoosh the top of your layer of food waste and bokashi bran down as flat as you can—remember, this is an oxygen-free process, so while you are building up your bucket, keeping as much air out of the bottom layers as possible is the goal.

  5. When Full, Let Ferment

    Once your 5-gallon bucket is full, keep it closed and untouched for at least two weeks. Some recommend letting it go a little longer, especially if you haven't chopped up your scraps so well.

    You want to be sure not to let any oxygen into the bucket. This is an oxygen-free process, so avoid the temptation to peek. While you are waiting for this bucket to ferment, you can start another bucket.

  6. Drain the Bokashi Tea

    Every 2-3 days during the 14-day fermentation period, drain the juice out of your bokashi fermentation system—this is where that spigot comes in handy.

    You can store this liquid or use it right away. For most plants, dilute 2-3 ounces of the bokashi tea per gallon of water and add to the soil. You can use it on houseplants as well as outdoor spaces. It won't attract pests and might even deter them.

  7. Bury or Compost Your Leftovers

    You will be left with what is basically a bucket of fermented, or pickled, food once the 14-day fermentation process is complete. This is sometimes called pre-compost because it's already partially broken down. It can be added to your regular hot or cold compost and will break down very fast, compared to non-fermented materials. Since it's so acidic, it won't attract flies or bugs of any kind.

    You can also simply bury this waste in your garden directly (in a fallow bed ideally) by digging a trench and filling it. Again, because of the acidity of the fermentation process, it won't be attractive to scavengers or bugs, and soil microbes will break it down in a couple of weeks.

Frequently Asked Questions

Will bokashi tea by itself really help my plants grow?

Yes, the liquid product from bokashi fermentation has been shown to improve plant yields by improving the nitrogen in the soil and providing an ideal carbon/nitrogen balance.

How do you know if your bokashi compost isn't working right?

It's fine if there's some white mold in the bin, but black, blue, or green molds or a foul smell indicate that something has gone wrong.

Should my fermented bucket look the same as when I added the food waste?

Yes, it will look very similar and food pieces will be identifiable—since this is a fermentation process, not a composting one. However, there have been significant chemical changes that might not be obvious to the naked eye which make this material different post-fermentation.

View Article Sources
  1. "Composting at Home." Environmental Protection Agency.

  2. Pandit, Naba Raj, et al. "Nutrient Effect of Various Composting Methods With and Without Biochar on Soil Fertility and Maize Growth." Archives of Agronomy and Soil Science, vol. 66, no. 2, 2020, pp. 250-265., doi:10.1080/03650340.2019.1610168