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Energy
Recovery from Municipal Solid
W ith its growing population and improved living standards, urban India generates 42 million tonnes of municipal solid waste (MSW) annually, 75 per cent of which is either landfilled or openly dumped. With such prevailing practices, land with disposed MSW will soon start encroaching human habitats. Urban settlements, in particular, with large population face this challenge which necessitates efficient MSW handling and management techniques that will maximise recycling and energy recovery.
MSW generated in India is predominantly organic in nature which has a total potential of generating 1700 MW power out of which only 17 MW has been so far installed in cities like Hyderabad, Lucknow, Vijaywada, Ludhiana, Surat and Chennai. Recent advances in scientific research have established the application of thermo-chemical (incineration, gasification and pyrolysis) and biochemical (anaerobic digestion and bio-methanation) procedure of converting waste to energy. The 6 MW power plant in Hyderabad uses 210 tons of refuse derived fuel (RDF) processed from 700 tons of MSW each day and has produced over 48 million units of electricity since 2003. A similar venture in Vijayawada uses 150 tons of RDF per day from 600 tons of MSW per day. In another private venture in Lucknow, a 5 MW plant is operational that uses 50,000 cu.m biogas from MSW and generates organic fertilizer as a by-product. Other small scale projects are also operational which are specific to the waste types that include market waste, slaughter house wastes and mixed waste. With the given scale of energy demand and the amassing MSW within and outside localities, there is huge potential to generate energy as well as dispose MSW off. Although the significance of electricity is undisputed, modern techniques can be used to provide a range of products that will cater to the needs of a community depending on its technological maturity. In this regard, pyrolysis appears to be significant in Indian energy scenario as it produces all three usable forms of energy – char (solid), producer gas (gaseous) and bio-oil (liquid). Pyrolytic studies on MSW have resulted in a healthy product distribution comprising of high quality char (32-49 per cent), producer gas (18-20 per cent) and bio-oil (30-50 per cent) 1, which can be potentially, used directly or indirectly, for household and/or community purposes. For instance, small size urban centers with population of 1 million will produce 270 TPD of waste (0.27kg/person/day)2. Considering a futuristic value of 60 per cent organic fraction in MSW (World Bank. 1999), 162 TPD will be available for energy recovery. Complete utilisation of that organic fraction in pyrolysis will produced 51-80 tons of charcoal, 30-32 tons of producer gas and nearly 48 tons of bio-oil. In addition, basic technical customisations will lead to maximisation of a particular product. As a result, the community gets to determine and produce its own fuel requirement as per the regional technological maturity. For example, charcoal production can be maximised in areas with predominant use of charcoal. Similarly, communities willing to upgrade to gas stoves can maximise produce gas output through temperature adjustments. Therefore, it can be easily imagined that on implementation of such projects in decentralised pattern, local centers of sustainable development will be created based on the amount of waste material effectively collected and pyrolysed. Private participation will further enhance the effectiveness of the project via objective planning and diligent monitoring.Disposing and effective handling of waste can have numerous positive impacts on resident population by eliminating disease vectors and creation of a pollution free habitat. People living in slums are more subjected to polluted and unhygienic localities where MSW handling and disposal practices are irregular. Efforts involving integrated actions to combine waste management and energy recovery techniques in communities placed adjacent to each other can not only provide a cleaner habitat to residents but also empower communities by proving usable forms of energy. q Arpan Pal 1 Characterisation of product from the pyrolysis of
municipal solid waste Buah W. K., Cunliffe A. N., Williams P.T., 2007
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