**3.2 Vermicompost**

Vermicompost (VC), the organic input, is produced from various organic wastes. It is a rich source of antibiotics, enzymes, immobilized microflora and various growth hormones like gibberellins which synchronize the growth of plants and microbes. It has the ability to improves the quality of growing plants and also increases growth resulting in improved metal toxicity. Vermicompost is a rich source of nutrients, increases the soil fertility. In contaminated soil, application of vermicompost improves soil physical and chemical characterstics of soils. Heavy metal contaminated soils are also bioremediated with vermicompost and spent mushroom compost. Bioremediation is done through vermiremediation. Vermiremediation is an applied science to get rid of heavy metals from soil. *Lumbricus rubellus* species were used to separate leachate-contaminated soil which contains various heavy metals [43]. It takes 90 days for its completion and the greatest reduction in the concentration of all heavy metals was approximately 50%. The vermicompost of urban waste also helps to reduce the risk of environmental contamination due to lower metal concentrations available in it [44]. The metal concentrations in earthworm's internal body were significantly and negatively correlated to heavy metal concentrations in the vermicompost. The higher bioaccumulation factor indicates higher metal accumulation in earthworm's tissue by which food chain is affected. The accumulation of metals in worm's tissue, not only remediate the metals from the urban wastes but also improves the quality of vermicompost by reducing the metal concentration. The ability of earthworms to mitigate the toxicity of heavy metals and to increase the nutrient content of organic wastes might be useful in sustainable land restoration practices. Heavy metals can bind with ligands of the tissues and thus lead to their bioaccumulation. The positive correlation was observed between metal concentrations in the earthworms and those in the soils with, which may be due to differences in bioaccumulation factors for different metals. Earthworms have the ability to inhabit and survive in contaminated sites with metals and have the ability to accumulate heavy metals in the cells of yellow tissue. Earthworm populations may develop a mechanism by which they can tolerate or resist the effect of metal-induced stress. Such tolerance is acquired by earthworms either through a variation in their genetic structure or reversible changes in an earthworm's physiology. Heavy metal pollution negatively affects the life history of earthworms such as growth, reproduction, and survival. The treatment of high phosphorus significantly reduced lead, zinc, and cadmium bioavailability to the earthworm which was due to the formation of metal-phosphate complex in the soils. The vermicompost reduced the ecological risk to soil-inhabiting invertebrates exposed to heavy metal contaminated soils. Earthworms act as an indicator for heavy metal toxicity that is present in the materials and are bio converted, indicating potential environmental hazard [45]. The capacity of earthworms to uptake and redistribute heavy metals in their body leads to a balance between uptake and

#### *Remediation of Soil Impacted by Heavy Metal Using Farm Yard Manure, Vermicompost, Biochar… DOI: http://dx.doi.org/10.5772/intechopen.105536*

excretion which helps them to survive in metal contaminated soil and also reported an increase in heavy metal content in the vermicompost of paper mill sludge. The increase was appreciably more for Fe and Cu. The weight and volume reduction due to the breakdown of organic matter during vermicomposting might have been the reason for the increase in heavy metal concentrations in vermicompost. The earthworm *L. terrestris* had the capacity to accumulate significant levels of zinc, and thus earthworm ingestion may result in zinc transfer to higher trophic levels [46]. Earthworms can also tolerate many heavy metals and pesticides in their body tissues and helps in remediation.
