Wednesday, December 17, 2008

Harvesting Your Compost

Depends on your worm bin setup and medium to worm ratio ( density ) , you may do the harvesting every 1 to 2 month for a healthy worm supply and a good mixture of castings and vermicompost. Some wonder why actually I’m differentiating casting and vermicompost ? What is the different ? I will explain this in detail in a short while.

When you are ready to harvest, you will notice that the volume of material has dropped substantially and the original bedding is no longer recognizable. The contents will now be brown and earthy-looking. There are several ways to harvest:

1. Move the contents of the bin over to one side. Add fresh bedding or medium to the vacant side. Put food waste in the new bedding. The red wigglers will gradually move over in search of food. After one or two weeks the finished compost can be removed.

2. Prepare new bedding. Dump the contents of the bin onto a large plastic sheet, and separate into small cone-shaped piles. Place a bright light above the piles. The worms
will move down away from the light. Remove the compost from the top. Repeat this four
or five times until a small pile of worms and compost remain. Place the worms and
the compost in the bin with fresh bedding.

3. Remove the entire contents of the bin. Put in fresh bedding and food. Place a large piece of damp burlap or the onion bag over the bin ensuring that the burlap / onion bag overhangs the edges of the bin and slightly touch the new bedding . Place one inch of vermicompost on top of the burlap / onion bag. With a bright light over the bin, the worms will move through the layer of burlap / onion bag and dive onto the newly prepared bedding, and you can remove the finished compost.


Note: For the second and third methods, don't feed the worms for one or two weeks prior to harvesting. If you do in bigger scale, a commercially available worm harvester will be a better approach.

This methods are not suitable to segregate the cocoons out from the castings ( if you interested on increasing the worm amount ) , you can use a small wire mesh ( as picture shown below ) to filter out the cocoons and can obtain a finer castings for selling. You can put back the bigger size castings together with the cocoons onto you newly prepared beddings for increasing your worm population. But beware , to much worms in a same bin ( density ) may caused the worms to race for food and indirectly reducing the reproduction rate.



Come back to the difference between casting and vernicompost. I tend to use the terms ‘worm castings’ and ‘vermicompost’ interchangeably here on the blog, when technically speaking they are not quite the same thing.

Worm castings are literally little worm poops - that is to say, material that has gone in one end of the worm and out the other. If you have 100% pure worm castings (virtually impossible to achieve) you should have a material that looks a lot like coffee grounds.

Vermicompost is really a more accurate term when it comes to the material produced in most worm composting systems. It is basically a mixture of worm castings, partially composted wastes, and any resistant materials that won’t readily break down. Really high quality vermicompost should have a high percentage of worm castings in it, but the chances of having every last bit of material in your system pass through a worm at least once is pretty slim.

Anyway - definitely not trying to split hairs here - just thought some of you might be curious about the technical difference between these two terms!

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