HARVESTING THE WORM BIN

WHEN TO HARVEST It may take two to six months for the worms to digest the contents of their worm bins, depending on amount of food, particulate size, and size of worm population. Worm manure, also known as vermicast and castings, will gradually build up. This is dark brown and soil-like in appearance. Its color and texture may vary according to what the worms are fed and the moisture content. For example, worms bedded peat moss will produce castings which are darker and fluffier than worms bedded in paper waste. To keep the worms’ living environment healthy you will need to periodically harvest the castings, as the worms find their manure somewhat toxic. You will know that your castings are ready to harvest when you there are few visible food particles left. Even so, enough bacteria, fungi, and protozoa may remain to support worms for quite some time. Eventually, the worms will breed less and begin to die if they are not allowed to escape into fresh bedding. The castings in turn can be used to fertilize your garden and indoor plants. How often you harvest the bin depends on how “finished” you desire the vermicast to be and whether the castings are for personal use or for sale. If the material is castings are for personal use you may not care if there are food bits left. If you are selling the worm castings, you will want a product which is consistent in color and texture and chemically stable. For the former I recommend screening the vermicast with a compost screen over a tarp or pail or using a mechanical harvester. Screening allows easy removal of undigested bits of food or bedding. If the vermicast is soggy, allow it to dry a bit on trays before screening . Screening produces a light, well-aerated, rich looking fertilizer you will be proud to share with others. The finer the screen the finer the texture. You may want to test for pH, nitrogen, potassium, and other nutrient levels using a maturity compost kit. Tests for heavy metals and other toxic substances are also available on line and through the Cooperative Extension Service in your county if you have special concerns.

Finished vermicast or worm castings is dark brown and resembles dirt. Photo source: The Autobiography of Squirmin’ Herman the Worm, University of Illinois Extension Service. http://www.urbanext.uiuc.edu/worms/

HOW TO HARVEST
There are different harvesting techniques for different styles/sizes of vermicomposting systems. Large-scale vermicomposting systems require large-scale mechanical harvesters. Although a home-sized harvester has recently become available for sale, small–scale and mid-scale vermicompost systems generally require more manual harvesting methods. We recommend the methods outlined below.

TOOLS YOU WILL NEED
A large, flat working surface, a plastic sheet or several large plastic bags, a garden fork, a large scoop or spatula, a bright overhead light or direct sunlight, at least one large pail or other container.

METHOD #1: Dump and Sort

• Prepare a smooth, flat work surface at least waist high for comfort (you will be looking down). Cover with a garbage bag or other slick material for easy cleanup. Arrange worm bin, empty container, garden fork and large scoop on work surface under a bright light(s).
• Remove layer of unfinished bedding/food from brown castings layer.
• Dump worm bin contents on work surface.
• Arrange contents in cone-shaped piles under a light(s). The worms will move away from the light towards the bottom of each pile. Over a period of several hours periodically scoop the top layer off each pile until the worms are massed at the bottom. It may take 20-40 minutes between passes.
• Place worms in small container, weight and document so that you know how many worms you have (1 lb = approx. 1,000 worms).
• Add worms back to fresh bedding in worm bin of origin or, if starting a new bin, add worms to an auxiliary worm bin filled with fresh bedding.

METHOD #2: Divide and Sort.
This harvesting technique requires less labor than Method #1.

• Prepare work surface as above.
• Remove contents from one side of worm bin and place in an auxiliary bin.
  Add fresh bedding and food to empty side. Over a period of weeks worms will move to the new bedding as they finish digesting the old bedding and food. This method of harvesting can be done starting at six weeks, although it may take as long as three months, depending on the size of the bin and how finished you wish the end product to be. The worm cocoons are usually in the upper six inches of the vermicompost and can be removed from the cured castings manually or with the aid of a fine mesh screen. Small home harvesters and commercial harvesters can do this automatically.

METHOD #3: Mesh Bag Lure
For this method of harvesting you will need some kind of small mesh bag like those used to package garlic and onions.

• Fill mesh bag with favorite worm foods such as melon or coffee grounds.
• Bury bag in worm bin bedding, leaving it there to attract worms from the surrounding bedding over time.
• When the food is gone and the bag is full remove it and empty into new bedding.

Leave castings in the original bin for finishing. Repeat mesh bag method in old bin to attract baby worms as they hatch from egg capsules, or cocoons.

WORM EGG CAPSULES/COCCOONS/CASINGS. Cocoons full of baby worms can be found scattered throughout the bedding and castings. As you screen the vermicast you may choose to pick out cocoons to add to your worm bin. This can be extremely time consuming, however, and unnecessary for the average worm bin owner. Some commercial worms farmers isolate the cocoons, add a protective coating, and sell them in pellet form.

WHAT TO DO WITH EXTRA WORMS
If you do not wish to expand your “worm herd” and the number of worm bins, you may choose to simply release your worms into a compost pile outdoors and let nature run its course. You may also choose to sell or give away your worms and teach others to vermicompost.

Good Luck from Melissa at Wormpost Northeast!

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