Vermicomposting: A Solution to Noxious Emissions in the South Asian Subcontinent
Abstract
One of the most significant threats to the environment is posed by the ever-increasing generation of waste. This has resulted in an urgent need for global waste management techniques that integrate the ideas of recycling and reusing of the essential components of waste. The current technologies of waste management including incineration, landfills, and material recovery have not proven as useful as intended. These mostly outdated methods have resulted in generation of toxic fumes, health hazards, and high energy and operation costs. Thus, a unique, safe, hygienic, and sustainable method of waste management is essential.
Vermicomposting is a low-cost, eco-biotechnological process of waste treatment in which earthworms are used to biodegrade the organic waste into useful nutrient-rich vermicast. The products of this waste treatment process are disinfected, detoxified and nutrient-rich bio-organic fertilizers. The process not only recycles organic wastes, but also helps improve soil structure and contents. This review provides an insight into the design, operation, commercialization, and factors affecting the vermicompost reactors.
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Introduction
According to the UN World Population Prospects, it is predicted that the world population will reach 9.74 billion by 2050. (United Nations, 2019) The ever-increasing human population has resulted in a significant increase in global waste generation and pollution. Approximately 1300 million tons (MT) of solid waste is generated annually in the major cities of the world, an amount projected to rise to 2200 MT by 2025. (Hoornweg & Bhada-Tata, 2012) Solid waste generation is positively related to the level of income and urbanization. On an average, developing countries including India, Pakistan, and Bangladesh, generate over 0.70 kg of solid waste per individual per day. (Troschinetz et al, 2009) It is estimated that 1.8 MT of solid waste per day will be generated in Asia alone by 2025. (Dasgupta, 2014; Yoshizawa et al., 2004) Table 1 compares the waste generation in Asia during the year 1995 and 2025 (projected values) (Hoornweg, 1999).
Waste disposal is a pressing issue, as the existence of widely spread waste imperils the environment in general and soil health in particular. The rapid development of human society creates imbalances in nature through rapid urbanization, industrialization, and infrastructure development, all of which cause deterioration of soil health. As the overall environmental milieu is polluted, humans are also affected.
When disposing waste, system complexities and the integrated nature of materials and pollution are quickly apparent. For example, waste incineration is expensive and poses challenges of air pollution and ash disposal. Incineration requires waste placed outside for collection to be containerized to stay dry, and much of the waste stream is not combustible. Landfills require land availability, and siting is often opposed by potential neighboring residents. Solving one problem often introduces a new one, and if not well executed, the new problem is often of greater cost and complexity. Most approaches to waste disposal lead to soil deterioration, toxic effects, and increased pollution of the land, air, and water and have an adverse impact on living beings in addition to the expense involved. To address this issue, we need an eco-friendly, one-step solution for managing wastes that also provides a beneficial end-product. TABLE 1 1995 AND 2025 MUNICIPAL SOLID WASTE GENERATION IN ASIA 4 GNP per Capita Urban Population (% of MSW generation (kg day-1 per capita) (USS) Total)
Country 1995 2025 1995 2025 1995 2025 Low Income 490 1050 27.8 48.8 0.64 0.6-1.0 Nepal 200 360 13.7 34.3 0.5 0.6 Bangladesh 240 440 18.3 34.3 0.49 0.6 Myanmar 240 580 26.2 47.3 0.45 0.6 Vietnam 240 580 20.8 39 0.55 0.7 Mongolia 310 560 60.9 76.5 0.6 0.9 India 340 620 26.8 45.2 0.46 0.7 Laos 350 850 21.7 44.5 0.69 0.8 China 620 1500 30.3 54.5 0.79 0.9 Sri Lanka 700 1300 22.4 42.6 0.89 1 Middle Income 1410 3390 37.6 61.1 0.73 0/8-1.5 Indonesia 980 2400 35.4 60.7 0.76 1 Philippines 1050 2500 54.2 74.3 0.52 0.8 Thailand 2740 6650 20 39.1 1.1 1.5 Malaysia 3890 9400 53.7 72.7 0.81 1.4 High income 30990 41140 79.5 88.2 1.64 1.1-4.5 Republic of Korea 9700 17600 81.3 93.7 1.59 1.4 Hong Kong 22990 31000 95 97.3 5.07 4.5 Singapore 26730 36000 100 100 1.1 1.1 Japan 39640 53500 77.6 84.9 1.47 1.3 Widely regarded safe and sustainable strategies to treat organic wastes include best-known practices of composting and vermicomposting for biological stabilization of solid organic wastes by transforming them into a safer and more stabilized material that can be used as a source of nutrients and soil conditioner in agricultural applications (Lazcano et al, 2008; Bernal et al, 2009). Vermicomposting is one of the most efficient means to mitigate and manage environmental pollution problems. It is the process in which earthworms are used to convert organic materials (usually wastes) into a humus-like material known as vermicompost. The goal is to process the material as quickly and efficiently as possible.
