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This overview of systems and operational projects describes factors which contribute to their success as well as the challenges that have forced sites to close.
MANY different approaches are being used to process large volumes of organic residuals with earthworms, ranging from relatively simple land and labor-intensive techniques to fully automated high-tech systems. Types of systems include windrows, beds, bins, and reactors. The largest vermicomposting facilities rely on tipping fees for feedstocks and accept a wide variety of organic materials. Smaller facilities usually have to purchase feedstocks or pay for transportation of materials.
Commercial in-vessel vermicomposting systems first appeared on the market in the United States in the early 1990s. The first mid-scale vermicomposting system was the Worm Wigwam, which was introduced in the Pacific Northwest by John Gorman-- Sauvage. About the same time, Al Eggen owner of Original Vermitechnology in Toronto, Canada - developed an automated, larger-scale vermicomposting system.
Operating mid-to-large-scale systems poses temperature control challenges that are seldom experienced with smaller operations. Larger systems generate more heat from decomposing organic materials and hold heat longer than smaller units. Operators also have to be concerned with solar gain in or around the system. Methods of lowering system temperatures include adding water, activating fans in or near the unit, and reducing the amount of feedstock applied.
Factors that may be considered for selecting the appropriate vermicomposting technology for a project include: Amount of feedstock to be processed; Funding available; Site and space restrictions; Climate and weather; State and local regulatory restrictions; Facilities and equipment on hand; and Availability of low-cost labor.
WINDROWS
Windrows are extensively being used both in the open and under cover, but require either a lot of land or large buildings. It is difficult to harvest the vermicompost without earthworms being included, so a mechanical harvester is commonly used with these operations.
The largest vermicomposting facility in the United States is operated by American Resource Recovery (ARR) in Westley, California. Managed by Mario Travellini and owned by Jim Davis, the vermiculture operation was begun in 1993 to build an earthworm inventory; four years later, ARR began processing and selling vermicompost. Currently, an estimated 500,000 pounds of earthworms process 75,000 tons of materials annually on 70 of ARR's 320 acres. The worms...