Compost Digester


Dispose of all your kitchen waste — raw or cooked meat, bones, dairy products, even pet feces — with a backyard food digester.

#1 Food Digester
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An outdoor compost digester is a system for enhancing decay of organic material in an almost completely enclosed container. Aside from the lid at the top, where feedstock is dropped, a digester has no openings save at the bottom where liquid is drained. The great advantage of compost digesters over traditional open-air piles is that one can compost almost any kitchen waste in a digester — meat, bones, some dairy products, even pet feces. (Be aware, that all instruction manuals say that one should never put compost made from pet feces where vegetables will be grown.)

However, some digesters cannot handle any yard waste and none can handle the quantities that a pile can absorb. Nor can they easily break down high-carbon or woody items. The wood chips and pine cones that may slow an outdoor pile will stop a digester completely.

Anaerobic versions can be as simple as a plastic bag full of garbage left in the sun or as complex as a barrel on bricks. (For an indoor version, see Bokashi Composting.) Interestingly, the only back yard anaerobic digesters on the market are designed for and sold as ways to dispose of pet waste. However, any of them can be used to digest food scraps and small amounts of yard waste.

If you are only composting food scraps and not pet feces, a home-made digester is perfectly adequate and making one is extremely easy. A garbage can with a tight-fitting lid works extremely well. Commercial anaerobic digesters are also available. The Greater Victoria Compost Education Center has a number of downloadable fact sheets available, one of them on digesters.

Anaerobic digesters have drawbacks. They are not quick. They produce methane rather than the less serious greenhouse gas carbon dioxide which aerobic composting produces. Their finished product often needs to aerate for several weeks to reduce its acids to levels that will not damage plants. Smells can be an issue. And the beneficial microbes that make compost so valuable an addition to soil do not grow in anaerobic conditions.

However, a well-maintained system can solve all these problems.

The aerobic digester avoids the environmental problems, both local and global, that can plague anaerobic systems. It won’t smell, since it doesn’t produce hydrogen sulfide. It won’t pollute (much) since it produces carbon dioxide rather than methane. This method is unusual because it is designed not to produce compost, but to dispose of kitchen scraps without allowing solids (compost) to build up.

Related Questions

  • What products to compost


    You will be able to source all of the essential elements in order to build a great compost pile without having to look too far! As long as your carbon to nitrogen ratio is optimal (25-30:1) your compost pile will be breaking down properly. Here are some lists of acceptable additions:

    Carbon Rich Material "Browns"
    Cardboard (free of dyes)
    Corn stalks
    Fruit waste
    Peat Moss
    Saw dust
    Stems & twigs

    Nitrogen Rich Material "Greens"
    Coffee grounds
    Kitchen food waste
    Garden waste
    Grass clippings
    Hedge clippings
    Vegetable scraps
    Weeds (that have NOT gone to seed)

    ​Things to Avoid
    ​Diseased plant material
    Colored paper
    Cat/dog waste
    Manures from carnivorous animals
    Citrus peels

    As for the rhododendron and holly leaves, you can definitely put them in your compost pile. However, it is a good idea to really chop or shred them up, as they take much longer to break down due to their fibrous and waxy make up. It really depends on how quickly you are trying to create usable compost. It might be a good idea to have a separate pile going that you incorporate those leaves into and another pile that you do not. That way you can have a pile you know will rapidly break down into garden goodness and have yet another ready to use later on. Good luck!