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. 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. It is difficult to harvest the vermicompost without earthworms being included, so a mechanical harvester is commonly used with these operations. Currently, an estimated 500,000 pounds of earthworms process 75,000 tons of materials annually on 70 of ARR's 320 acres. The worms are fed paper pulp generated from recycled cardboard, tomato residuals, manure, and green waste in three-foot wide windrows, some of which are a quarter mile long. During its busiest season, ARR ships up to 100 tons of vermicompost per week.