Green Okinawa (9) Recycle your kitchen waste into compost

Dear OISTers,

With the 'Green Okinawa' series, we are seeking to learn from each other about how to be more environmentally friendly in Okinawa.

Here’s our post on how to recycle your kitchen waste and turn it into compost to fertilize your garden or potted plants.

 

Climate benefits of recycling food waste

You can reduce how much ‘burnable trash’ you send to the incinerator every week by recycling your kitchen waste and making compost. What’s more, the nutrient-rich compost will put extra flowers on your hibiscus and extra passion in your passion fruits (maybe)! Here are some tips about how to do it in Okinawa.

 

Outdoor composting

To create compost outdoors you can buy heavy duty plastic compost bins from some garden centers including Make Man in Gushikawa. You can also build your own simple structure made from wooden pallets (here is a link to a tutorial).1 Ask about wooden pallets at your local JA garden center.

Whichever method you opt for, you need a space outdoors which is somewhat protected from typhoons and heavy rains. Choose a spot away from the entrance of your home to help keep insects and wildlife at bay. Placing some heavy stones or cinder blocks in the bottom of the compost bin help to anchor and stabilize it. Securing it with rope to your garden fence is another good ways to prevent it from toppling over in heavy winds. Keep the lid on your outdoor compost bin to stop it getting filled with water in a storm.

You can compost both kitchen waste and garden waste in your outdoor compost bin. It is good to add a layer of brown (dry) matter like potato peel, corks and dirty cardboard bento boxes followed by a layer of green (wet) matter  like raw fruit and vegetables, edamame pods, banana skins, used tea leaves and coffee grounds. Avoid adding anything that is tough to degrade like coconut shells. You can add fish, meat and cooked food (even in the Okinawan climate) as long as it`s not too much at once. This is an excellent FAQ for common questions for outdoor composting.2

For composting outdoors in a very humid and rainy climate like in Okinawa, David from the OIST gardening club recommends attracting black soldier flies to your compost heap and adding lots of dry, carbon-based matter.

 

Indoor methods

If you don’t have an outdoor space, you can still set up a composting system in your home.

  • Cardboard box method

This simple way to recycle food scraps has become very popular in Japan. You first line the cardboard box with some absorbent ‘base material’ e.g. sawdust, coco peat, kuntan (rice husk charcoal), bamboo powder. You can buy these base materials in Tabata and other garden centers in Okinawa. Each day, you mix in your kitchen waste.  Cover the cardboard box with an old T-shirt or tea towel. The kitchen waste is exposed to lots of oxygen which is great for the aerobic composting process and prevents bad smells.  Hiroko Tabuchi, originally from Japan and now living in New York writes about her cardboard box composting (read her articles here and here).3 Find instructions and diagrams from Nagoya city hall here and from Ie village here.4-5

 

  • Bokashi method

The Bokashi composting method was invented in Okinawa! Bokashi “ぼかし” is a Japanese term meaning ‘Fermenting Organic Matter’. Unlike other composting methods which need plenty of oxygen, this method is anaerobic. You mix your kitchen waste with ‘Bokashi mix’, which ferments and rapidly breaks down the kitchen waste. Bokashi mix is made up of bran material and ‘effective microorganisms’ (EM’s). The invention of modern Bokashi method is credited to Professor at University of Ryukyu’s here in Okinawa, Dr. Teuro Higa.6 With this method you can compost all your usual kitchen waste as well as fish, meat and dairy, items can be raw or cooked. The process produces a liquid, which is a great plant fertilizer.

You can buy Bokashi mix from most garden centers in Okinawa including the JA Farmers Market in Yomitan (opposite the Village hall). Bokashi composting bins with a tap to easily drain off the liquid are available online from Amazon.jp.  and all the parts to make your own are available at Tabata.

Collect your kitchen waste in a container with a tight lid. Each time you add your kitchen waste to your container sprinkle a layer of Bokashi mix on top and press it down to get rid of the extra air. When you take off the lid it will have a mild smell of vinegar, and when the lid is closed there should be no smell. Drain the liquid regularly. You can dilute it 100:1 and water your plants with it. When your Bokashi bin is full, add a final layer of Bokashi mix and let the contents ferment and reduce in size (keep draining the liquid regularly). After about 3 weeks, your kitchen waste will be fermented. It will be in a semi-solid state and you can dig it into your soil, bury it in a hole in the ground, or add it to an outdoor compost heap. The longer you wait, the more it will keep breaking down and reducing in volume. You need to keep draining the liquid.

“Bokashi is the best way I've found at home, and you can easily make a DIY mixture from woodshavings/cardboard and EM-1. Get a container with a tight lid and be sure to drain the tank often so it doesn't smell. The solid volume of waste will be reduced and the compost tea can be diluted and used on houseplants/garden”. David, OIST Gardening Club.

Read about Bokashi composting in a small apartment in Tokyo in ‘Zero Waste Japan’ here and other practical tips here.7-8

 

What to do with the resulting compost

  • If you have your own garden, patch of soil, or potted plants
     
    • Mix the compost into the soil. David from OIST’s Gardening Club recommends digging your compost into your garden soil or potted plants rather than apply directly to the surface since compost made outdoors in Okinawa can often be quite wet.
    • Dig a hole in the soil in your garden, add the compost and cover over.
       
  • If you don’t have your own garden
     
    • Use the TIDA ‘Market Place’ on the OIST intranet or other online platform, like BooKoo Okinawa to find someone who would like to use your compost.
    • Talk with a friendly local farmer or neighbor that gardens and offer them your compost.
      •  “Hello, I am composting at home, would you like to use my compost for your garden or vegetable patch?”
        ➡自宅でコンポストを作っていますが、こちらの畑で使っていただけますか?
      • “Shall I leave you some compost here tomorrow”?
        ➡明日ここにコンポストを置いておきましょうか?
    • OIST gardening club maintains a compost heap. If you are employed at OIST or are a family member, please get in touch with David Simpson <david.simpson@oist.jp>  to enquire about accessing it.

 

Do you compost your kitchen and garden waste? Share your tips and pics with us and we’ll improve the post. Do you have compost to give away or could you use some extra for your potted plants? Put a note on TIDA and see how fellow OISTers can help.

Read previous Green Okinawa tips here https://groups.oist.jp/resource-center/green-okinawa

This Green Okinawa post was developed in collaboration between Mai Barnes (OIST Resource Center), David Simpson (OIST Gardening Club) and Kate Whitfield.

 

References

  1. How to build a compost bin, Gardeners' World Magazine, https://www.gardenersworld.com/how-to/diy/how-to-build-a-compost-bin/
  2. Composting Frequently Asked Questions, Moray Council, http://www.moray.gov.uk/moray_standard/page_57692.html
  3. Hiroko Tabuchi, New York Times, 2020 https://www.nytimes.com/interactive/2020/05/19/burst/compost-box-indoors-coronavirus.html and https://www.nytimes.com/2020/05/06/climate/new-york-coronavirus-composting.html
  4. How to make cardboard compost, 2016, Nagoya city hall http://www.city.nagoya.jp/kankyo/page/0000060262.html
  5. How to make cardboard compost, 2015, Ie Village website https://www.iejima.org/document/2015021600052/file_contents/jissenhen.pdf
  6. Teruo Higa, Wikipedia, https://en.wikipedia.org/wiki/Teruo_Higa
  7. Japanese Bokashi Composting for Apartment Living, Zero Waste Japan http://thezerowastejapan.com/a-composting-guide-for-apartment-living/
  8. Learn how to bokashi like a pro, Own your impact,  https://ownyourimpact.com.au/news/learn-how-to-bokashi-like-a-pro