Use of Vermicomposting Biotechnology for Recycling Fly Ash as a Source of Plant Nutrients

Abstract

Large scale generation of fly ash from increasing numbers of coal fired plants is now emerging as a global environmental threat. To combat the situation, emphasis is being given on recycling of this waste material for various productive purposes. Since fly ash contains many plant nutrients in appreciable amount, it’s re-use as a source of these nutrients forms an important component of such efforts. However, the major problem associated with supply of plant nutrients through fly ash is the low availability of most of the nutrients in this material despite their good occurrence in total amount. This behavior is attributed to inert nature of this burnt material. Since vermicomposting helps in accelerated degradation of various kinds of wastes through earthworm gut microorganisms, we assessed the possibility of enhancing the availability of different plant nutrients in fly ash through this biotechnology. The results of a series of yard as well as on-farm studies showed that introduction of epigeic earthworms in mixtures of fly ash and organic wastes helped to stabilize the organic matter and enhance the microbiological activity in the substrates. These, in turn, helped to improve the availability of three major nutrients viz. N, P and K in the composted materials. It was further observed that substantial shares for such increments came from degradation of fly ash. Onfarm trials showed use of vermicomposted fly ash to be able to compensate the application rates of fossil fuel based chemical fertilizers to 40 – 50 % without compromising the yield of the crops. Status of different soil health attributes were also found to be in acceptable ranges under these treatments. A protocol for vermicomposting of fly ash, developed through systematic studies on screening of suitable earthworm species, maintenance of optimum composting condition, use of varying kinds of organic wastes etc, has been discussed