Handbook of Vermicomposting by E.SREENIVASAN - HTML preview

CHAPTER 1

INTRODUCTION

  Rapid industrialization, urbanization, and the ever-increasing population generate voluminous solid wastes. In recent years, disposal of organic wastes has caused serious environmental hazards and economic problems. Burning of organic wastes contributes tremendously to environmental pollution thus, leading to polluted air, water and land. This process also releases large amounts of carbon dioxide in the atmosphere, a main contributor to global warming together with dust particles. Burning also destroys the soil organic matter content, kills the microbial population and affects the physical properties of the soil. A substantial portion of this solid organic waste is non-toxic. On  one  hand  tropical  soils  are deficient  in  all necessary plant nutrients  and on  the other hand huge quantities of  such nutrients  available  in solid organic wastes. Treatment of solid organic wastes has therefore become an essential part of the waste management programmes almost all over the world. Existing methods to its treatment and disposal are rather expensive. Vermicomposting technology is one of the best options available at present for the treatment of organic wastes. The term vermicomposting is coined from the Latin word ‘Vermis’ meaning the ‘worms’. Vermicomposting refers to natural bioconversion of biodegradable garbage into high quality manure with the help of earthworms.

Earthworms play a key role in soil biology; they serve as versatile natural bioreactors to harness energy and destroy soil pathogens by feeding voraciously on all biodegradable refuse. They are nature’s way of recycling organic nutrients from dead tissues back to living organisms. They have faithfully done their part to keep this cycle of life continuously moving for more than 20 million years. Ancient civilizations including Greece and Egypt were the pioneers in recognizing the role of these worms played in soil. Earthworms were considered as “sacred” by the Egyptian Pharaoh, Cleopatra who recognized the role played by worms in fertilizing the Nile Valley croplands. The role of earthworms in waste stabilization has been known for many years, especially in Southeast Asian and European countries. Attracted by the nature and activities of burrowing earthworms in soil, Charles Darwin carried out studies on the significance of their activities for over 39 years.  He wrote this about these tiny creatures,” It may be doubted whether there are many other animals in the world which have played so important a part in the history of the world.” He also called them as unheralded soldiers of the land, in his last and final book “The Formation of Vegetable Mould, Through the Action of Worms, With Observations of their Habits” which reported how these organisms feed and convert organic materials (Darwin, C.,1881). 

From then on, studies have been carried out to find out their role in maintaining the soil fertility and also in the degradation of the organic matter present in the soil. These works also included investigations into the possibility of utilizing earthworms for the break down of organic wastes such as animal wastes, vegetable wastes and municipal solid wastes (MSW). Earthworms convert a portion of the organic matter into worm biomass and respiration products, and expel the remaining partially stabilized matter as discrete material (castings). In this process, earthworms and the microorganisms act symbiotically to accelerate the decomposition of organic matter. The driving forces behind the introduction of vermiculture and other reuse processes, is the global recognition of the need to recover organic material and return this to the natural cycle.

Vermicomposting is generally defined as the aerobic decomposition of organic residues by exploiting the optimum biological activity of earthworms and micro-organisms. The process depends upon the earthworms to fragment, mix and promote microbial activity in the organic waste material. The earthworms ingest organic solids and convert a portion of it into earthworm biomass and respiration products and egest peat like material termed as vermicompost. As compared to the thermal composting, vermicomposting generates a product with lower mass, high humus content, processing time is lower, phytotoxicity is less likely, fertilizer value is usually greater, and an additional product (earthworms) which can have other uses is produced.

Organic waste materials which are biodegradable in nature may be used as substrates for the vermicomposting process, provided that the materials do not contain anything harmful to earthworms. For example, the byproducts of agro-industrial processing offer potential opportunities to be used as substrates for the earthworms and microorganisms. The agro-industrial wastes are huge source of plant nutrients and their disposal means the ultimate loss of the resourceful material. At present, these wastes are either grossly underutilized or completely unutilized due to in situ burning in the fields or land disposal to the surrounding areas. These individually and cumulatively agro-industrial wastes could effectively be tapped for resource recovery through vermicomposting technology for use in sustainable land restoration practices.

 Some of the major agro-industrial wastes explored for vermicomposting are shown in Table.1and Fig.1

Table.1: Details of agro-industrial organic wastes for vermicomposting

Fig.1: Agro-industrial wastes for vermicomposting

Coir waste                        Saw dust              

Sugarcane trash                             Wood waste