FOCUS ENVIRONMENT Prof GK Roy
Full exploitation of the energy potential from a renewable source like the USW is highly warranted from the dual point of view of the eco-friendly disposal of garbage as well as partly meeting the energy security
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BLURB
Around 550 tonne per day of USW produced from the twin city — Cuttack and Bhubaneswar — is going to be utilised for production of energy. A 600-tonne capacity USW incineration plant to generate 11megawatt electricity is going to come up soon at Bhuasuni at a cost of Rs.200crore.
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According to a new research conducted by the World Watch Institute — an independent research organisation dedicated to environmental concerns — rising prosperity and the increasing urbanisation of world population could lead to a doubling in the volume of Urban Solid Waste ( USW) generation by 2025. This would largely go up from its present volume of 1.3billion tonne per year, challenging environmental and public health management endeavours in the cities of the world.
United States leads the world in USW output at 621,000 tonne a day with China at the second position with 521,000 tonne. However, the top ten USW-producing countries include four developing nations — Brazil, China, India and Mexico — due to the size of their urban population and, in part because their urban dwellers are prospering and adopting a high-consumption lifestyle.
USW is a mixture of vegetable and non-vegetable wastes in cooked and uncooked stages, leftovers, packaging of different kinds, papers, plastics, rags and other fabrics, dust, ash and a variety of combustible and non-combustible matter. USW excludes the trade and industrial wastes that contain a variety of toxic and hazardous materials.
With rapid migration of rural folk to urban areas, particularly in the developing countries, USW is being produced at an ever-increasing rate. It is estimated that by 2050, 50 per cent of Indian population will be living in urban areas. USW generated in urban India was 1,88,500 tonne per day in 2012. As per estimates, solid waste generation in small, medium and large cities and towns in India is about 0.1kg, 0.3-0.4kg and 0.5kg per capita per day respectively. The estimated annual increase in per capita waste generation is about 1.33 per cent per year. With an annual increase rate of 5 per cent of USW, urban India will generate 440,000 tonne of waste by 2041.
In spite of the fact that the per capita generation of USW is comparatively low in developing countries like ours (0.4-0.5kg against 2.4kg in the US), the financial involvement in the collection and disposal of the refuse by traditional methods has been quite high. Municipalities spend 20-50 per cent of their available recurrent budget on USW management. As an example, Greater Mumbai Corporation’s budget for USW management was Rs.15.5billion in 2010-11. The civic body spends Rs.1160 per tonne on collection, transport and disposal of USW with collection and transport constituting 80 per cent of the cost. In India, the average municipal expenditure on solid waste management is Rs.500-1500per tonne. Yet, it is also common that 30-60 per cent of all the USW in developing countries is uncollected and less than 50 per cent of the population is served.
USW composition is related primarily to the standard of living and dietary habits of the population. The composition from cities of the developed countries vary from that of the developing ones. While mixed paper, rag and textile form a sizeable fraction in the USW of the developed countries, food and vegetable waste (organic waste) and ash and fines predominate in the USW of developing countries. An average composition of USW from Indian cities include: paper -5.7 per cent, textile- 3.5 per cent, plastic- 3.9 per cent, metal-1.9 per cent, glass-2.1 per cent, ash and fine earth etc -40.3 per cent and compostable organic waste-41.8 per cent. The composition also changes with time (change of habits) and depends on the population of the cities.
The simple and economic method of waste disposal is the ‘open dump’ system, wherein unprocessed refuse is dumped in low-lying areas in the city outskirts with little regard to public health and aesthetics. The obvious evil consequences are serious problems of groundwater pollution, fire hazard and rodent infestation. A more acceptable sanitary landfill method which reduces the above threat to the environs is by composting and covering the garbage with dirt. However, this practice is also losing ground. Acceptable sites, if available, have to be located far from habitation centres.
Energy recovery from waste is the conversion of non-recyclable combustible materials into electricity and heat. Currently, in the US, 86 facilities for the combustion of USW have the capacity to produce 2720megawatt of power per year by processing more than 28 million tons of USW. Complete utilization of USW has been achieved in Sweden. The country is virtually pollution-free and the streets of its cities are clean of garbage. Yet this enviable situation is causing a paradoxical problem. Sweden relies on burning its waste to provide electricity and heat to hundreds of thousands of homes. But, the country is now running short of garbage — the raw material for energy production. As a result, the nation of 9.5million citizens must now import rubbish to feed its Waste-to-Energy (WtE) incineration power plants. Each year, the Scandinavian country imports 80,000tonnes of garbage mostly from Norway to fuel homes and businesses. Norway pays Sweden to take away its excess garbage. Sweden then burns it to generate electricity and heat and then sends the ashes left behind which contains many highly polluting toxins back to Norway for disposal in landfill.
The Union ministry of new and renewable energy has predicted that there exists a power generation potential of about 1,500megawatt from the USW generated in India. The government is actively promoting Waste-to-Energy technologies by providing various incentives and subsidies to WtE projects. But, according to the Indian Renewable Energy Development Agency (IREDA), only about 2 per cent of the potential has been tapped in India so far. Around 550 tonne per day of USW produced from the twin city — Cuttack and Bhubaneswar — is going to be utilised for production of energy. A 600-tonne capacity USW incineration plant to generate 11megawatt electricity is going to come up soon at Bhuasuni at a cost of Rs.200crore.
Against the backdrop of the dwindling non-renewable and conventional fossil fuel energy source like coal, petroleum and natural gas to meet the ever-increasing energy requirement of a developing nation like ours, the full exploitation of the energy potential from a renewable source like the USW is highly warranted from the dual point of view of the eco-friendly disposal of the garbage as well as partly meeting the energy security.
The writer is a retired Director and Professor of Chemical Engineering, NIT, Rourkela
