The Basics of Bokashi Composting

A Method Using Fermentation

Composting
cjp / Getty Images

Nearly every gardener (or would-be gardener) knows that that composting is a good practice for the garden and for the environment, but not everyone knows there are many ways that composting can be practiced. At a basic level, all composting is a process by which organic materials are deliberately decomposed in a controlled fashion to produce a material that can be used to return nutrients to the soil. The "recipe" for traditional composting is a mixture of "green" materials that are high in nitrogen, "brown" materials that are high in carbon, along with air and water.

But within that broad definition, there are many ways to practice composting. There is simple on-site composting in which pretty much all organic scraps and refuse (except for meat products) are heaped together and allowed to decompose; there is vermicomposting (using red worms to hasten the breakdown of organic materials); there is windrow composting (high volume composting using long rows of organic materials that are aerated regularly); there is static-pile composting; and there is in-vessel composting.

Bokashi composting is yet another method of composting that is quite different than other methods. While it takes some special equipment and materials, Bokashi composting requires only about 10 days to convert organic materials into a useable material, and the nutrient value of the material is among the highest of any method of composting.

How Bokashi Composting Works

Bokashi is a Japanese word meaning "fermented organic matter." Developed in the early 1980s by Dr. Teuro Higa, a professor at the University of Ryukyus, Okinawa, Japan, the method involves layering kitchen scraps (vegetables and fruits, as well as meat and dairy scraps) with a Bokashi inoculant in a special bucket. Usually, the inoculant consists of either wheat germ, wheat bran, or sawdust combined with molasses and effective microorganisms (EM). The bran/molasses serves as the food for the microorganisms, which are the same natural microrganisms found in soil. You can buy complete kits for getting started in Bokashi composting from garden stores and natural living retailers, which also sell the replenishment products, including the effective microorganisms and bran/molasses.

The Bokashi bucket has an air-tight lid and a spigot at the bottom to drain off the liquid that is produced. The liquid must be drained off to prevent the bucket from developing a somewhat foul odor, but the liquid serves as a very nutritious "bokashi tea" that can be used to fertilize houseplants.

When layered and left to sit out of direct sunlight, the mixture quickly begins to ferment, and within 10 days the fermented mixture can be dug directly into the garden or added to a compost pile to finish its decomposition. In essence, the bokashi process is a fermentation process rather than a traditional composting method.

Unlike traditional composting, which is an aerobic process that requires oxygen, Bokashi is an anaerobic process that requires that you isolate the materials from oxygen as much as possible. The bucket should be opened only to add scraps, not to check on the materials. Some people recommend pressing the food waste into the composter to squeeze out the air, then leaving a plate (or another flat object) resting on top of the material to shield it from exposure to oxygen.

Advantages and Limitations of Bokashi Composting

Bokashi composting has several advantages over other styles of composting, but there are also limitations you should be aware of.

Pros of bokashi composting:

  • The method allows for the use of dairy and meat scraps that are not incorporated in other forms of composting.
  • Bokashi composting can be done in a relatively small space, since it does not require materials to be fluffed up with air.
  • The resulting product makes for a highly nutritious plant food that can be buried in compost trenches in a garden.
  • The liquid byproduct makes an excellent fertilizer tea for feeding plants directly.
  • The fermented material makes excellent food to add to a vermicomposting (worm composting) bin.

Limitations of bokashi composting:

  • The material produced is a fermented product, not a traditional compost that can be surface applied to a garden as a mulch. It must either be buried in trenches in the garden or added to a traditional compost heap for further breakdown.
  • The process requires a special airtight bucket or bin with the ability to drain off liquid that is produced.

Bottom Line

Bokashi composting is categorically different than other forms of composting since it is an anaerobic process that ferments organic material rather than fully decomposing it. Although it requires special equipment and materials, bokashi composting produces byproducts in a very short time that are highly nutritious for plants and can serve as "fuel" for other forms of composting.