The solid wastes generated as a result of human activity have become very complex. Unscientific management of such wastes has resulted in environmental pollution, thereby putting a serious risk to the ecosystem and human health. A sustainable waste management is required for reduced pollution levels as well as for safeguarding the environment for future generation. Biological methods have gained in importance mainly because of its environmentally friendly option for recovering materials and energy. This is true as per the guidelines of “Hierarchy of Sustainable Waste Management.” Composting and anaerobic digestion are two treatment options that is commonly followed in both developing as well as developed countries. The aim of this chapter is thus to address the technical background, advantages, as well as shortfalls related to the waste treatment via biological methods. An up-to-date literature thus presented may be beneficial to the scientists and researchers for working towards further improvement of the present system of waste management.
TopIntroduction
Growing population, fast economic growth, rapid urbanization and changing lifestyle patterns has resulted in a catastrophic increase in the production of solid wastes. Undesirable solid by-products resulting from human activities are known as solid wastes, which have no economic value and hence are disposed off (Ojoawo and Agbede, 2011). Depending on the human activities, solid wastes are categorized into municipal solid wastes (MSW), industrial wastes, clinical wastes and hazardous wastes (Sridhar, 2000). MSW are generated from household activities, gardening activities, commercial activities, agricultural activities, sewage facilities etc. Solid wastes like sludge generated from domestic and industrial wastewater treatment plants are also included under MSW. Organic wastes generated from industries and hospital generated wastes are also classified under MSW but in some countries such has been segregated under industrial or clinical wastes. Inorganic wastes like ash, metal and wastes with hazardous nature, exhibiting properties like flammability, explosiveness, causticity, and toxicity are included in hazardous waste. Thus, MSW is the highest contributor to solid wastes.
The volume of solid wastes generated has been observed to vary depending on various factors like population density, income, life style etc (Fantola, 1997). As per a survey conducted during 2018 by T.Wang on global population and solid waste generation (Fig 1), China and India lead the share of global population (approximately 18% each) and are also the highest contributors of solid waste generation (15.55% and 11.95% respectively). A similar research conducted by Verisk Maplecroft (Idris et al., 2004) on waste generation and recycling indices in 2019 revealed that over 2.1 billion tonnes of solid waste are generated globally each year. Out of which only 16% is recycled each year and the remaining 46% is disposed off unscientifically and unsustainably. As per data projected by the World Bank(datatopics.worldbank.org), waste generation has been expected to increase to 3.40 billion tonnes by 2050 which is more than double the population growth expected across the same time period. As per Fig 2 (source: The World Bank), it is estimated that the daily rate of waste generation in developed countries would increase by 19% while the same for low income countries would increase by 40%.In India, as per Central Pollution Control Board (CPCB, 2000), a survey conducted in 2000 by Ministry of Urban Development showed that total solid waste generated was 100,000MT and the per capita waste generation rate was 0.3-0.76kg/day. The amount of waste generated per capita was estimated to increase at the rate of 1.33% annually (Sharholy et al., 2008). As compared to data in 1947, Indian cities generated 8 times more solid waste and the major reason cited was increased urbanization and changing life styles.
Figure 1. Share of global population in contribution to solid waste generation
Figure 2. Projected waste generation in millions of tonnes/year (source: The World Bank)