Vermicomposting systems using earthworms range from very simple methods
involving low technology such as windrows, waste heaps, or containers, through
moderately complex to completely automated continuous flow reactors (Edwards, 2004).
The basic principle of all successful vermicomposting systems is to add the wastes at
frequent intervals in small, thin layers to the surface of the system and allow the
earthworms to move up and concentrate themselves in the aerobic upper 15 cm of waste
and continue to move upward as each successive waste layer is added. Many of the
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operations involved in vermicomposting can be mechanized; a suitable balance is needed
between the costs of mechanization and the savings in labor that result. The key to
combining maximum productivity of vermicompost with the greatest rates of earthworm
growth is to maintain aerobicity and optimal moisture and temperature conditions in the
waste and to avoid wastes with excessive amounts of ammonia and salts. The addition of
organic wastes in thin layers avoids overheating through thermophilic composting,
although enough usually occurs to maintain suitable temperatures for earthworm growth
during cold winter periods. Hence, for year-round production, to maintain a reasonable
temperature in temperate climates, the processing should always be done under cover,
although heating is not usually necessary if the waste additions are managed well with
addition of thicker layers during cold periods to provide some degree of thermophilic
composting. Temperature may need to be decreased under cover in summer with fans.