Earthworms as Organic Waste Managers and Biofertilizer Producers

Vermicomposting is the processing of organic materials by earthworms into homogeneous and humus-like material known as vermicompost. It is a complex mixture of fecal matter of earthworms and microorganisms. In vermicomposting system, earthworms act as voracious feeder, modifying composition of organic waste, gradually reducing its organic carbon and C: N ratio and retains more nutrients (nitrogen, potassium, phosphorus, calcium). The nutrient content is generally higher in vermicompost than in the traditional compost. Earthworm increases the surface area of any material and makes it more favorable for the activity of microbiota for further decomposition. Earthworms have the ability to consume various types of organic wastes such as livestock excreta, cattle dung, oil palm waste, agricultural residue, sewage sludge and other agro-industrial refuse. Studies suggested that organic wastes can be managed by the use of different species of earthworms and the production of vermicompost as a powerful biofertilizer in sustainable agriculture discouraging the use of chemical fertilizers. Vermicomposting accelerates the bioconversion process by two to five times as compared to traditional composting, thereby hastens the conversion of wastes into valuable biofertilizer. In the present review, earthworms are described as waste managers in utilizing and changing the physico-chemical properties of the organic wastes and highlight the need for the use of vermicomposting in organic waste recycling. Earthworm-microbe interaction and the nutrient status of final vermicompost are also discussed in detail.