Composting indoors: the Bokashi method

Recently we’ve been looking for composting methods that are accessible to people who don’t have gardens. We’ve been experimenting with worm farming, including making mini worm farms in buckets. This month we’d like to share the bokashi fermentation method, which is thought to have its origins in Korea, though the modern system was popularised in Japan.

How it works

Step 1: fermentation

Food waste is sealed into a small airtight bin that can be kept on a kitchen counter. Bokashi bran is added, which contains bacteria that ferment the food. After 2 weeks, the fermented food is partially broken down.

Step 2: finishing the composting process  

The fermented food is then moved to a new location to fully break down into nutrient-rich compost. You can do this by: 

  • Putting it in a container planter (ideal if you don’t have a garden). Fill the container with 1/3 potting soil, add your fermented food waste and mix with the soil. Cover with soil and wait 2 weeks before planting.
  • Adding it to an outdoor garden waste compost bin.
  • Adding it to a worm farm in small amounts, until the worms get used to it (it’s very acidic).
  • If you have a garden, you can dig a trench in a garden bed and bury it.

If you want to keep composting continuously, it’s a good idea to get two buckets so that you can fill one bucket and start filling the other bucket while the first bucket is fermenting. 

Does it smell?

Because the process happens in a sealed container without oxygen, there shouldn’t be a problem with nasty smells or pests. The bacteria that breed in the bin produce lactic acid. This acidic environment means that bacteria that produce nasty smells can’t survive.

Benefits of bokashi

Nutrient rich compost and liquid fertiliser

As well as turning the solid waste into nutrient-rich compost, a liquid is produced, which can be harvested from a tap. This is highly acidic and can be used to clear drains! Alternatively, you can dilute it down to use it as a plant fertiliser. Just dilute it 1:100 with water.

Pre-processing waste you can’t put in other compost bins

Bokashi can be used to pre-process waste that wouldn’t normally go into an outdoor compost bin or worm farm, such as cooked foods, dairy and meat. While placing unprocessed food waste into outdoor composters can attract rats, they will steer clear of bokashi-fermented food waste. 

How much does it cost?

Bokashi bran can cost around £6 a kilo, though this will go a long way so it works out fairly economical. Bokashi bins can cost £35-45, though you can also make your own bokashi bin easily…

DIY bokashi bins

The process for making a bokashi bucket is very simple: all you need is 2 buckets and a drill! You can install a tap for drainage, though this is optional. See step-by-step guide.

For a more information about the bokashi method, check out this guide:

Want more tips on avoiding food waste and growing your own food?

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Image attribution
  1. Bokashi bin set Pfctdayelise, CC BY-SA 3.0, via Wikimedia Commons
  2. Bin contents Pfctdayelise, CC BY-SA 3.0, via Wikimedia Commons
  3. Fermented contents of bin Zenyrgarden, CC BY-SA 4.0, via Wikimedia Commons
  4. DIY bokashi bin Zenyrgarden, CC BY-SA 4.0, via Wikimedia Commons
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