Anaerobic Composting

Bokashi_Anaerobic CompostingAnaerobic composting or composting without the presence of oxygen has been practiced for centuries. Records indicate that the Chinese are the oldest known civilization to practice this form of composting to fertilize their rice paddies.

In more technical terms, anaerobic composting is composting organic materials, using living anaerobic organisms such as bacteria in an environment that has no oxygen present. This is the same process you will find occurring in nature as peat bogs and marshes.

Unless you happen to have access to a large field of water you are going to have to find another way to create your anaerobic compost pile. While most composting experts will talk about not letting your compost piles get too wet or they will rot, anaerobic composting requires approximately 70% moisture levels in order for it to work properly.

The Standard Compost Pile

You can turn your current compost pile into an anaerobic one quite simply and effectively by adding plenty of water. Yes I know we have spent hours telling you how important it is to maintain moderate to low moisture levels, but with this type of composting you need to remove the oxygen from your compost pile. The water will drive out the oxygen and keep it out if you keep the water level high enough. By covering the pile to help keep in the moisture, you will end up with a slimy mess, which indicates that it is working properly. You should however, be prepared for a very odoriferous compost pile. This is really more suitable to households with larger tracts of land where the aforementioned odoriferous pile can be placed away from the house or the neighbors.

The Submerged Pile

This method of creating anaerobic compost is very similar to that which is has been in use by the Chinese for centuries and involves keeping your compost under water. For this you will need a large tank, plastic pool or tank that is big enough to hold your compost and then be filled with water. As your compost pile decomposes the odors are trapped in the water. While slightly more involved than a standard anaerobic compost pile, your neighbors will certainly appreciate it.

anaerobic composting in a fieldThe Big Bag Theory

You have probably seen this method in use in the local farmers’ fields, this would be the long white bags that lay in the fields over the winter. This version is a little simpler and a lot smaller. You can use a large heavy duty plastic garbage bag. You first layer the bottom of the bag with soil or cured compost, then add your compost and add enough water to make everything moist. Seal the bag so that no air can get in and roll it to get things started and then leave it alone for 6-8 weeks.

No Hole in My Bucket

Off all the different forms of anaerobic composting, the bucket method is perhaps the easiest and least offensive. This is a long term project and will take up to a year to create the compost you are looking for. You simple cut the bottom from a five gallon bucket and plant it a few inches into the ground. You then fill it with your scraps and organic waste, place the lid on it and forget it for a year. Do not open until the year has passed or you will let in more oxygen and ruin the process. As you can see a fair amount of patience is required for this method. At the end of the year you will have perfectly usable humus. All of these forms of anaerobic composting work well, some will produce more compost than others, while at the same time creating a rather smelly situation.

Bokashi Composting

Bokashi_Anaerobic CompostingYou may have heard of Bokashi composting.

It is an anaerobic form of composting using a bucket but easier to manage than the hole in the ground method and with much faster results.

Click here to read reviews about Bokashi.


  1. G’day Jenny,
    Great advice. When I made my 1st huge compost heap years ago I was blown away by the heat generated. Ended up with great compost, but the local possums beat me to the vegies !!! Next attempt will feature a 2 metre fence !

  2. Compost King says:

    Happy Possums Harry. Fence sounds like a good idea.

  3. Sounds like there’s a lot of science behind composting. I had never heard of anaerobic composting before. And yes I’d always thought that you had to keep water away from composting. Anaerobic composting sounds like a longer term form of composting, as it takes about a year of uninterrupted peace to come to fruition. That means you’d probably use this composting technique in addition to others that you could add more compost to as you go.

  4. Hi,Compost King.
    I love this site so many great tips some I have never heard of before and will now be using as I am not allowed to have a bin here now he wont even know I am composting :-)

  5. Hello Composting Tips,

    Sounds like a great way for composting with water and keep it moist. Never knew there was so many different ways to compost scraps and use in the garden. So love coming here to read what tips/hints you have about composting.


  6. Compost King says:

    Thanks Lisa, glad you are finding the information interesting.

  7. I have had renewed interest in this topic after reading that anaerobic composting may help hold onto a greater portion of essential nutrients (especially Nitrogen) that are lost during aerobic composting. Do you know if there is any merit to this? It makes sense to me that nitrogen is lost in aerobic – thus the need to keep adding more but I am unsure about anaerobic. I have read that if you smell ammonia from your anaerobic pile, you should add more carbon as you are losing nitrogen (ammonia=NH3)

    • Compost King says:

      Hi Steve
      That is an interesting question you raise. I believe that anaerobic composting does result in fewer nutrients lost. The smell can be a problem, however this can be overcome by keeping the pile submerged under water. If you are thinking of using bottomless bins in a garden for anaerobic composting make sure the contents are kept moist and the smell should not be a problem. I would be hesitant to add carbon rich materials to an anaerobic pile as this could slow down the process. Have you thought about Bokashi composting which is an anaerobic form of composting?

  8. Hi Compost King:

    I am interested in anaerobic composting for a delicate wilderness site. My plan is to use several five-gallon buckets, wet down the material to be composted, and seal the buckets with the standard snap-on lid. My question is whether the gasses produced during composting will generate enough pressure to pop off the lids. I’d rather not vent them for odor control. I have the space to let these buckets sit for up to two years if necessary. Trying to avoid a compost explosion if possible :)

    • Compost King says:

      Hi Karl
      A compost explosion wouldn’t be pleasant. :) I think you would need to make sure that the lids were secured really well otherwise they may pop off and your anaerobic composting would be ruined. It is probably a matter of trial and error. Let us know how you get on. it sounds interesting.

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