Composting: How to Select a Worm Bin

 

Worm bins are available in a variety of materials, shapes, and sizes.  The type of bin you select for vermicomposting will depend on where you plan to keep it, how much waste you will compost, and personal preference.

Material

Worm bins must have good air flow and drainage so most bins are made out of wood or plastic.  Wood is preferable because it absorbs a certain amount of moisture and the lid allows plenty of air flow.  Plastic bins can be used but even with drainage holes they tend to “sweat” and build up too much moisture on the inside.  The restricted air flow in a plastic bin can also results in an unhealthy environment for the worms as anaerobic microorganisms start to take over.  The anaerobic environment produces a smelly bin, another definite downside. Plastic bins also don’t last as long as a well constructed wood bin and may leach undesirable compounds into your compost.

 

Size

The size of your bin depends on where you plan to keep it and the amount of waste you would like to compost.  Since worms feed upwards in the top layer of bedding, a shallow bin with more surface area is preferable to a deep container.  An ideal bin should be no more than 12-18 inches deep according to expert Mary Appelhof, author of Worms Eat My Garbage.  To determine the overall size bin for your household, keep track of your food waste for a week and select a bin with one square foot of surface area for each pound of garbage per week.

Example:

A household produces an average of 6 pounds of worm appropriate waste each week.  They would require a bin that is approximately six square feet (e.g., 2′ wide x 3′ long x 1′ deep).

 

Type

There are three types of worm bins:

Single Bin

The single bin is a simple box without any dividers.  You can build one out of wood or use a large plastic box.  The single bin is the easiest to build but the most difficult to harvest.  You start with a layer of bedding and add your worms and organic material.  When your compost is ready to be harvested you must sift through the castings to remove any worms.  The harvested compost can now be used in your garden and the worms can be returned to the bin to start a new pile.   Why go through the trouble of sifting out the worms?  Composting worms won’t survive in your garden (they are different than the earthworms usually found in soil) and if you don’t save them in your bin for the next batch of compost then you’ll have to purchase more worms.

Pros:  Small, easy to build

Cons:  Difficult to harvest

 


Vertical Migration Bin

The vertical flow bin is made of trays stacked on top of each other.  Each tray has a mesh bottom allowing the worm “tea” (liquid runoff from the castings) and worm castings to drop through to the lower trays while the worms stay in the upper tray where the organic waste is added.  The bottom tray can be pulled out to harvest the castings without having to worry about sifting through the worms.  These bins have less than two square feet of surface area and therefore are better for households with a very small amount of compostables.

Pros:  Relatively easy to harvest, small footprint

Cons:  Holds less and produces less, more complex to build, often made out of plastic

 

FSC Cedar Compost BinHorizontal Migration Bin

The horizontal migration bin looks similar to the single bin on the outside but has a vertical mesh divider effectively splitting the box into two sections.  Each section is used in the same way you would use a single bin.  When the compost in one section is ready to harvest, the other section is filled with bedding and organic waste.   In a couple weeks most of the worms will migrate through the vertical mesh divider into the new section to munch on the fresh scrap.  The “finished” compost in the first section can be harvested without worrying about sifting through to remove the worms.

Pros:  Easiest of the three types to harvest

Cons:  Larger than the single bin (a pro for households who require a larger bin)

 

Where to Buy

Wood Bins

EcoBuzz Garden offers a variety of horizontal migration bins built with FSC certified cedar.  We can also custom make any type of bin in any size using FSC certified cedar – send us an email with the dimensions and we’ll be happy to provide you with a price quote.  More details…

FSC Cedar Compost Bin

 

 

 

Plastic Bins

You will also find the plastic vertical migration bins in our store:

Worm-Factory-360-Worm-Composter-0-6

 

Next Step:  Worm Bin Bedding

Looking for an introduction?  Read the worm composting primer:  Vermicomposting Primer

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