Vermicomposting vs Composting


What are the similarities and differences in composting systems that can be operated in open or in-vessel systems - with or without worms?
Reference and sighting researched by: Tanya Vece

(Re-print of media material from BioCycle April 1997, pages 57-59)

THE IMPORTANCE of biological processes in the management of animal organic wastes has been widely recognized. Within the broad range of bioprocesses available, this report deals with the two which are the most efficient for converting solid organic residuals into useful products - composting and vermicomposting. The purpose is to compare the advantages and disadvantages of the two processes.

Open systems of composting can be summarized as follows: Windrow composting consists of placing the mixture of raw materials in long narrow piles or windrows which are turned mechanically on a regular basis to aerate the piles. Turning alone often does not ensure consistent oxygenation. Within an hour after turning, oxygen levels in a pile often drop drastically, and microbial activity is correspondingly reduced. For this reason, the pile must be turned frequently, leading to technical and economic problems.
Moreover, pile size is another important consideration, because piles higher than three meters become difficult to aerate. In forced aerated static piles, a blower provides air to the composting mass. No turning of the materials is needed once the pile is formed. There are basically two ways to oxygenate the piles: Bottom suction draws air through the pile by the imposition of negative pressure. In this kind of ventilation, height is a critical factor. With piles greater than 2.5 to three meters, it becomes almost impossible to get uniform aeration.

These piles must be blanketed with an insulating layer (usually cured compost) to ensure a uniform distribution of temperature. Bottom blowing is used where aeration is provided by blowing air through the pile (positive pressure). This method tends to cool and dry the bottom layers of the pile, leaving the outer layers warm and moist. In alternative ventilation systems, bottom blowing aeration is alternated with bottom suction aeration. The alternative air movement leads to a homogenization of temperature and moisture throughout the pile.

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