Vermicomposting: Changing Environment Through Changing Perspective

When it comes to waste, most of us try to stay as far away from it as possible. The mere sight of a dumpsite and its unpleasant odor makes us feel disgusted even though we are the one generating it in the first place and not being able to manage it efficiently. With passing years and increasing population, waste generation is also on the rise and the world can hardly keep up at this rate. According to World Bank, the world generates 2.01 billion tonnes of municipal solid waste annually and it could grow up by 70% by 2050.

Despite of being a basic need for maintaining public and environmental health, with the rapid urbanization process and lack of coherent operational system, middle and low-income countries are struggling to ensure an efficient solid waste management system. Level of development among countries make a significant difference in their waste characterization, hence influencing the scale and available technologies of recycling certain types of wastes over others. For example, in low and middle-income countries biowaste can account for 50-60% of the total waste whereas in high-income countries its only 30-35%.

Most of the low and middle-income countries choose open dumping and unequipped landfills to dispose of their waste. Such actions contribute to soil, water and air pollution through GHG emission, leachate leakage and pose great threats to public health as well. For countries like Bangladesh where more than 70% of the waste is composed of biowaste, recycling technique like vermicomposting on large scale have huge potential to retrieve the value of waste as well as reducing the amount of waste going to the landfills.

Vermicomposting uses worms to convert organic wastes into a humus-like material called vermicompost. This compost is actually the excreta of earthworms which is very rich in nutrients. There are about 3000 species of earthworms found around the world. Red Wigglers (Eisenia foetida) and Red Earthworms (Lumbricus rubellus) are the most used species of earthworms in vermicomposting.

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Plant based wastes are best suited for vermicomposting, however animal and dairy based wastes should be avoided. For the worms to work effectively, some conditions should be fulfilled like, the temperature should range between 15-30 degree celcius. They should be kept in a shaded and moist condition with the moisture content between 70-85%. Acidic pH is harmful for the worms. So, neutral or slightly higher pH is recommended. The worms should be provided with bulky, carbon rich bedding typically made of shredded paper or cardboard. Stocking density is recommended between 2.5-10 kg/sq. m. For the worms to easily process the waste, it should be reduced in particle size less than 5 cm. The worms can process about 50% of waste equivalent to their body mass per day. So, feeding rate can be adjusted according to that.

Vermicompost contains an average of 1.5% - 2.2% N, 1.8% - 2.2% P and 1.0% - 1.5% K. The organic carbon is ranging from 9.15 to 17.98 and contains micronutrients like Na, Ca, Zn, S, Mg and Fe. Chemical analysis of the castings shows that it contains 5 times the available nitrogen, 7 times the available potash and 1.5 times more calcium than that found in 15 cm of good top soil. (Ruz-Jerez, Ball & Tillman 1992)

Along with vermicompost, worms and worm tea are the byproducts of vermicomposting. Worm Tea is actually the leachate from worm bins which is highly nutritious and used as liquid fertilizer. Earthworms are high in protein, up to 65% with essential amino acids and thus considered good probiotic feed for fish and poultry.

Vermicomposting can be operated at small scale household level using worm bins, medium scale neighborhood level or even in large scale facilities. Apart from reducing the amount of waste, practicing vermicomposting have great economic and environmental value too. According to the Ministry of Agriculture, Bangladesh has a yearly demand of approximately 5 million tons of fertilizer and 68 percent of the fertilizer had been imported in FY15 (Dhaka Tribune, 2016). Encouraging the use of vermicompost among farmers will reduce our dependence on imported fertilizer as well as chemical fertilizers which requires huge amount of energy to produce and also harmful for soil in the long run. It has been estimated that about 10-15% reduction in GHG emissions could be achieved through landfill mitigation and diversion, recycling and other forms of solid waste management and vermicomposting play an important role here.

So, rather than avoiding the situation and considering waste as filthy, changing our perspective towards it and working to get the best out of waste though vermicomposting, we surely can bring positive change in our environment. We need a new outlook, transforming disgust to demand.

 

References:         

• Ruz-Jerez, B.E., Ball, P.R. and Tillman, R.W., 1992. Laboratory assessment of nutrient release from a pasture soil receiving grass or clover residues, in the presence or absence of Lumbricus rubellus or Eisenia fetida. Soil Biology and Biochemistry, 24, pp.1529-1534.
•        UNEP (2015). Global Waste Management Outlook.
•       https://www.wastedive.com/news/world-bank-global-waste-generation-2050/533031/