Bokashi Composting - The Art and Science of Fermenting Kitchen Scraps
(Editor's Note: This article was originally published on September 3, 2007)
“Bokashi” is a Japanese term meaning “fermented organic matter”. In Bokashi composting, an “EM Inoculant” is sprinkled over food waste in an airtight container. EM Inoculant is an inert carrier, such as rice hulls, wheat bran or saw dust, infused with effective micro-organisms or EM. . The EM are natural lactic acid bacteria, yeast, and phototrophic bacteria that act as a microbe community within the kitchen scraps, fermenting and accelerating breakdown of the organic matter. Once the fermentation is complete, the compost can be buried or placed in a modified compost pile to complete its decomposition. The end product is rich, dark compost, ready for the garden.
We’ve now been using bokashi and refining our technique for three years. When we first started there were only a couple of internet references to bokashi composting. Now many sites exist. Even one with a video. Many of the sites originate from island countries, where governmental agencies are promoting the technique, presumably to save on landfill space and promote returning biomass to the soil. If you decide to give bokashi composting a try, there is now a lot of support and additional information.
How it’s done
The bottom of the container is sprinkled with EM inoculant. All solid kitchen waste, including meat is added to the container and, at the end of the day, inoculant is tossed on. After a few days, the waste develops a pickled smell. This odor is not something you’d want to use as perfume but it certainly beats the smell of putrefaction. Once the container is full, it can be parked outside to continue fermentation and a second container brought in for fresh scraps. My family of five takes about 1 week to fill a five-gallon container.
After a couple of weeks sitting in the container outside, the waste is still present in its original shape and color. A white mold may be present on the top. The smell can be strong, but is not putrid. At that point, it can be buried in a hole in the yard a couple of feet deep.
However, fermented waste can’t be buried right next to plant roots, as it is somewhat acidic. So, when our landscaping was more or less complete, we constructed a permanent “bokashi” collection site. My husband cut off the bottom of a garbage can, we buried it a few inches in the ground and added a container of fermented garbage then covered the waste with a layer of soil and leaves. These layers can be built up over time and periodically mixed with a compost mixer.
We also add Bokashied waste to the middle of our conventional compost pile. The fermented waste is protected by a couple of milk crates to shield it from curious rodents. More waste can be added every three weeks or so as the original batch vanishes. Once all fermented odor is gone, the residual waste can be tossed with the rest of the debris in the pile. This system has created the first warm compost pile I’ve ever had with temperatures getting up to 120 degrees. The final compost is beautiful; crumbly, rich dark and brown.
Some web site incorrectly advertise Bokashi composting as odorless. It’s definitely not odorless. Flies, rodents and raccoons will be attracted to fermented waste as long as it has a detectable smell. Occasionally a batch of bokashi compost will “go off” in the container and develop a strong putrid smell. Usually an “off” container contains too much liquid or not enough inoculant.
Fermentation occurs in oxygen free (anaerobic) conditions, so fresh air needs to be excluded. So a good container to collect fermenting garbage in needs a tight lid and should fit in the kitchen. A clean, 5 gallon paint container with a snap-on lid works well and can be found at any hardware superstore. Some plastic kitty litter containers work well too. Fancy bokashi containers are for sale in catalogs and over the Internet. These have a tray in the bottom to hold the fermenting garbage up out of the liquid that accumulates and a spigot to siphon off the liquid. The liquid is full of micro-organisms and can be diluted and added directly to the soil. We have one of these containers but rarely remember to tap the liquid. A 5-gallon picnic-style beverage dispenser with a spigot might work too.
Making your own EM Inoculant
A bran-micro-organism combination is called “inoculant”. Pre-prepared inoculant can be purchased on-line. However, it’s far less expensive to make at home. The organisms can be added to any inert material readily available such as rice hulls, wheat bran and saw dust. I purchased “effective micro-organisms (EM)” from a company on-line. Micro-organisms are a bit of a “blind item” and buying them on-line requires a leap of faith. Included with the packing slip were fairly easy to follow instructions for making the inoculant.
Molasses (grocery store)
Chlorine Free Water (well water or tap water aged in a open container for a day)
Wheat bran (Agricultural Store)
Effective micro-organisms (also known as EM, Order On-Line)
Plastic bins or garbage can
Weather protected spot outdoors such as a porch or carport .
Warm but not too humid weather.
The working time is 1-2 hours depending on batch size and how smoothly things go.
Bran is spread out on a tarp and mixed with a solution of water, molasses and EM. The key point is getting the desired consistency. Bran squeezed in a fist should hold together but crumble easily and not drip any liquid. I ended up needing to make more of the liquid than originally called for to get the desired consistency. The mixture is then shoveled into plastic storage bins or garbage cans to grow for about a month in warm weather. Happy growth is indicated by a white fuzz and a yeasty smell. The bran-microbe combo is spread out to dry and then stored in plastic bins or bags. Our family of five has been using the batch I made from 50 lbs of bran now for about three years. This fall, I may need to make another batch.