**1. Introduction**

Increasing world population has resulted in higher consumption of goods and services that has driven a substantial increase of organic wastes originating from households, industry, and agriculture [1]. Much of the organic wastes are highly infectious as they contain a variety of pathogenic microorganisms. Dumping of organic wastes in open areas generates serious environmental issues such as the accumulation of heavy metals in soil, pollution of ground and surface waters due to leaching and run-off of nutrients. These organic wastes when applied directly to agricultural fields cause soil environment-related problems including phytotoxicity [2]. These wastes represent a valuable organic resource, which could be

recycled and transformed into nutrient rich fertilizer and/or soil conditioner [3–5]. Moreover growing awareness about adverse effects of agricultural chemicals on human health has increased interest in organic agriculture [6]. Organic agriculture also promotes ecological conservation due to judicious use of natural resources [7–9]. In demand for safe and sustainable strategies to treat organic wastes includes best known practices of composting and vermicomposting for biological stabilization of solid organic wastes by transforming them into a safer and more stabilized material that can be used as a source of nutrients and soil conditioner in agricultural applications [10–12]. Vermicomposting is one of the most efficient means to mitigate and manage environmental pollution problems [13]. Recently, many studies are being done to establish vermicompost as one of the preferred organic substitutes to chemical fertilizers [14, 15]. Vermicompost is more rich in NPK, micronutrients and beneficial soil microbes (nitrogen fixing and phosphate solubilizing bacteria and actinomycetes), an excellent growth promoter and protector for crop plants [16, 17] than compost [18, 19].

#### **1.1 Vermicomposting- a preferred approach in organic farming**

Vermicomposting (vermis from the Latin for worm) is a mesophilic process [20] which involves a joint action of earthworms (active at 10–32°C) and mesophilic microbes [21] for the conversion of organic wastes into a valuable end product known as vermicompost. Whereas, composting involves the degradation of organic waste by microorganisms under controlled conditions, in which the organic material undergoes a characteristic thermophilic stage that allows sanitization of the waste by elimination of pathogenic microorganisms [22]. Composting is also used to treat manures, green wastes or municipal solid wastes [23]. However, vermicomposting gives a higher-quality end product than composting due to joint action of enzymatic and microbial activities that occur during the process [24]. This process is faster than traditional composting as the material passes through the earthworm gut, whereby the resulting earthworm castings are rich in microbial activity and plant growth regulators, and fortified with pest repellence attributes as well [25, 26]. Compared to traditional composting method, vermicomposting also results in mass reduction, shorter processing time, and high levels of humus with reduced phytotoxicity [27]. Thus, vermicompost is considered an ideal manure for organic agriculture as it is nutrient rich and contains high quality humus, plant growth hormones, enzymes, and substances that are able to protect crops against pests and diseases [28, 29]. Moreover, vermicompost has high porosity, aeration, drainage, and water-holding capacity [20]. In addition to increased N availability, C, P, K, Ca and Mg plant nutrient availability in the earthworm casts are also found [30]. Plant growth hormones namely cytokinins and auxins are found in organic wastes processed by earthworms [31]. They also release certain metabolites, such as vitamin B, vitamin D and similar substances into the compost [32]. Thus, earthworms accelerate the mineralization rate and convert the manures into casts with higher nutritional value and degree of humification than traditional method of composting [33]. The composition of commonly available nutrients in vermicompost is as follows: Organic carbon 9.5–17.98%, Nitrogen 0.5–1.50%, Phosphorous 0.1–0.30%, Potassium 0.15–0.56%, Sodium 0.06–0.30%, Calcium and Magnesium 22.67–47.60 meq/100 g, Copper 2–9.50 mg/kg, Iron 2–9.30 mg/ kg, Zinc 5.70–11.50 mg/kg, Sulfur 128–548 mg/kg [34]. Hence, vermicomposting enables biological transformation of wastes into a valuable organic fertilizer [35, 36]. Vermicompost is popularly called as black gold and has become one of the major components of organic farming system [26].

**47**

*Vermicomposting: An Effective Option for Recycling Organic Wastes*

Earthworms are invertebrates belonging to the phylum Annelida, class Oligochaeta and family Lumbricidae. The earthworms are long, elongated, cylindrical, soft bodied animals with uniform ring like structures consisting of segments along the length of their body outwardly highlighted by circular grooves called annuli. On the ventral surface of sides of the body each segment bears four pairs of short, stubby bristles, or setae used for its movement. Earthworms have an opening at the anterior end is mouth and the one at the posterior is anus. Earthworms possess both male and female gonads, so are called as hermaphrodites. They deposit their eggs in a cocoon without any larval stage. At the time of egg laying, the sexually mature worms contain a distinctive epidermal ring just beneath the anterior segments called, clitellum, which has gland cells to form a viscid, girdle like structure known as cocoon. The number of fertilized ova in each cocoon has 1–20 lumbricid worms.

There are about 3320 species of earthworms all over the world [37], but hardly 8–10 species are suitable for vermicompost preparation. Earthworms have been extensively utilized for the recycling of a variety of organic wastes like municipal solid wastes [38] wheat straw [39], sewage sludge [40], forestry waste [41], vegetable waste [42], farmyard manure [43], sorghum stalk, wheat straw, paddy straw [44], coir pith [45]. Renowned scientists, Charles Darwin called earthworms as the 'unheralded soldiers of mankind', and Aristotle described them as the 'intestine of earth', as they could digest a wide range of organic materials [46, 47]. On the basis of morphoecological characteristics, earthworms have been classified into three categories [48]; Anecic (Greek word "out of the earth") – these are burrowing worms that only come to the surface at night to drag food down into their permanent burrows deep within the mineral layers of the soil. Endogeic (Greek word "within the earth") – these are also burrowing worms but their burrows are typically more shallow and they feed on the organic matter inside the soil, so they come to the surface only rarely. Epigeic (Greek word "upon the earth") – these worms live on the surface litter and feed on decaying organic matter. They do not have any permanent burrows. These "decomposers" are the type of worm used in vermicomposting. Two tropical species, African night crawler, *Eudrilus eugeniae* (Kinberg) and Oriental earthworm, *Perionyx excavates* (Perrier) and two temperate ones, red earthworm, *Eisenia andrei* (Bouche) and tiger earthworm, *Eisenia fetida* (Savigny) are extensively used in vermicomposting [49–51]. Most vermicomposting facilities and studies are using the worms *E. andrei* and *E. fetida* due to their high rate of consumption, digestion, and assimilation of organic matter, tolerance to a wide range of environmental factors, short life cycles, high reproductive rates and endurance and resistance during handling [52]. A few other species *Drawida nepalensis*, *Lampito mauritrr. Dichogaster* spp., *Polypheretima elongate, Amynthas* spp. *Dendrobaena octaedra, Eisenia hortensis* [53] have also been

*DOI: http://dx.doi.org/10.5772/intechopen.91892*

**2.1 Biology of earthworm**

**2.2 Classification of earthworm**

used for composting under specific conditions.

**2.3 How does earthworm facilitate vermicomposting?**

Earthworms promote the growth of "beneficial decomposer aerobic bacteria" in organic waste material and also act as a grinder, crusher, chemical degrader and a biological stimulator of waste material [54, 55]. Earthworm hosts millions of decomposer

**2. Role of earthworm in vermicomposting**
