Introduction 

Aristotle called worms the “intestines of the earth” and stated that there may not be any other creature that has played so important a role in the history of life on earth. Earthworms constitute a large part of biomass (living bodies) inhabiting soil. In recent years efforts have been made to use the potential of earthworms in recycling of nutrients, waste management and development of vermicomposting systems at commercial scale. These are also called as “Ecosystem engineers” as they increase the numbers and types of microbes in the soil by creating conditions under which these creatures can thrive and multiply. The objective of this article is to present an overview of the vermicomposting technology. 

In India, the integration of crops and livestock and use of manure as fertilizer were traditionally the basis of farming systems. But development of chemical fertilizer industry during the green revolution period created opportunities for low-cost supply of plant nutrients in inorganic forms which lead to rapid displacement of organic manures derived from livestock excreta. The deterioration of soil fertility through loss of nutrients and organic matter, erosion and salinity, and pollution of environment are the negative consequences of modern agricultural practices. In India, millions of tons  of livestock excreta are produced annually (Table 1). Odour and pollution problems are of concern. Currently the fertilizer values of animal dung are not being fully utilized resulting in loss of potential nutrients returning to agricultural systems. The potential benefits of vermicomposting of livestock excreta include control of pollution and production of a value added product.   Vermicomposting of different livestock excreta including cattle dung; horse waste; pig waste; goat waste; sheep waste; turkey waste and poultry droppings has been reported.  Organic wastes can be ingested by earthworms and egested as a peat-like material termed “vermicompost”. Recycling  of wastes through vermicomposting reduces the problem of non-utilization of livestock excreta. During vermicomposting, the important plant nutrients such as N, P, K, and Ca, present in the organic waste are released and converted into forms that are more soluble and available to plants. Vermicompost also contains biologically active substances such as plant growth regulators.  Moreover, the worms themselves provide a protein source for animal feed.

Composting, Vermicomposting and Vermiculture

Composting  is bioconversion of organic matter by heterotrophic microorganisms (bacteria, fungi, actinomycetes and protozoa) into humus-like material called compost. The process occurs naturally provided the right organisms, moisture, aerobic conditions, feed material and nutrients are available for microbial growth. By controlling these factors the composting process can occur at a much faster rate. 

Vermicomposting  is the process by which worms are used to convert organic materials (usually wastes) into a humus-like material known as vermicompost.  The goal is to process the material as quickly and efficiently as possible. Vermiculture  is the culture of earthworms. The goal is to continually increase the number of worms in order to obtain a sustainable harvest. The worms are either used to expand a vermicomposting operation or sold to customers who use them for the same or other purposes.   

If the goal is to produce vermicompost then we want to have maximum worm population density all of the time. If the goal is to produce worms then we keep the population density low enough that reproductive rates are optimized.