Abstract of the presentation on ‘Waste to Energy’ Waste and Energy are two facets of development. A better lifestyle typically demands higher usage of energy. The per capita power consumption of US is 12 times that of India while China consumes almost 5 times equivalent. Conventional sources of energy such as coal and oil, though easy to use, are limited in availability, have a skewed distribution across geographies and cause pollution that leads to Global warming. India has one of the largest power deficits in the world with a current power shortage of 8% on average and 12% at peak demand. With continued economic growth and rapid industrialisation, the gap between the supply and demand of power is only expected to increase further.This is a major issue threatening to derail the growth story of many developing countries including India. The other side of development is the amount of waste generated per person. An average American generates about 800 Kg of municipal waste per year, while the figure is around 150 Kg for urban India. This is on the rise as consumption rises in tune with economic development. Simple land filling is not enough to deal with the waste generation both with respect to availability of land for disposal and environmental impacts of land filling. The above two challenges coupled with the fact that average municipal solid waste has substantial carbon content has led to growth of the waste-to-energy sector in the last two decades. Though the exact techniques of energy recovery may vary, there seems to be substantial scope of recovering valuable energy out of waste. The sector has seen cyclical growth patterns, the peaks being driven by high energy prices, advances in technology, government regulations regarding landfills etc and the troughs being caused by stable energy prices, environmental activism, political pressures, and alternate choices of using waste. Waste to Energy (WTE) is part of the solid waste management hierarchy, together with recycling and land fill. The waste management hierarchy starts with waste avoidance/reduction at the top, followed by resource recovery and ends with disposal. WTE fits with both the second and third levels of waste management hierarchy. At first glance, WTE facilities and most of the other thermal conversion technologies emit greenhouse gases, primarily carbon dioxide. However, upon investigation, WTE facilities actually reduce greenhouse gas emissions as compared to disposing of wastes that are not recycled into a landfill. The goal of zero waste and full recycling is a very distant goal. Europe
which has set standards for the waste management industry is able to recycle about 70% of waste and uses WTE techniques for dealing with the rest. Several technologies have been tried out with varying degree of success. Processing waste to make RDF and burning it in thermal steam-turbine plants has been in practice since almost two decades now. Aerobic and anaerobic digestion to generate methane and then generating heat or power has also been practiced successfully across the world. Waste pyrolysis and gasification technique aims to produce liquid and gaseous fuels by heating the waste under strictly controlled pressure, atmospheric and moisture conditions that prevent combustion from occurring. Plasma arc reduction is a relatively new technique which uses a very high temperature to vaporize the organic components to elemental hydrogen and carbon atoms that combine to make natural gas. The process leads to maximum waste reduction though the economics of the process remain to be established. The presentation would attempt to review the various WTE technologies that are in operation and their relative performance. It would review the current status of the sector globally and in India and try to establish the contours of the future landscape. Ramanarayana Parhi VP Business Development Selco International Limited.
A presentation on
Waste To Energy
By Ramanarayana Parhi
Vice President, Selco International Limited
Contents
1 2 3 4 5 Introduction to WTE The arguments for and against Types of WTE technologies WTE in Indian Context Future outlook and Conclusion
Introducing Waste to Energy
Waste-to-energy (WTE) or energy-from-waste (EFW) refers to any waste treatment that creates energy in the form of electricity or heat from a waste source Most WTE processes produce electricity directly through combustion, or produce a combustible fuel commodity, such as methane, methanol, ethanol or synthetic fuels
Opposition to WTE
We should aim at a zero-waste society WTE conflicts with concept of waste reduction and recycling Composting is better for the environment and is required for farming Waste incineration causes air pollution WTE is not financially viable
Waste Management Hierarchy
D E S I R A B I L I T Y
Statistics on Solid Waste in India
CPHEEO estimates a per capita waste generation in Indian cities and towns in the range of .2 to .6 kg/per day. India generates 1.2 million tonnes of solid waste, 4.4 million tonnes of hazardous waste and 4.45 million tonnes of plastic waste everyday Higher income group generates more than 3 times the waste compared to lower income group Urban India generates 3 times more waste than rural With rapid urbanization, rise in population and changing consumer patterns, India is all set to witness a four to five fold rise in waste generation in the coming years
Source: http://globalis.gvu.unu.edu
Why Waste to Energy
Conserving fossil fuels by generating electricity and heat Reducing greenhouse gas emissions from landfills Recovering ferrous and non-ferrous metals No aqueous emissions that can be expected from landfills Reducing space requirements of landfills Source of renewable energy
Industry Scenario
Growth in Waste to Energy sector has been cyclical Current spurt in interest is fuelled by:
Advances in equipments (boilers, grate systems, air pollution control systems) Sky high fossil fuel prices Changes in landfill regulations thus requiring closure of existing landfills and restrictions In creating new ones Comparison of air pollution from different sources of power WTE Plants produce electricity “with less environmental impact than almost any other source of electricity” – US EPA
Source: (O’Brien,SWANA, 2005)
Where WTE is most preferable
Crowded urban areas Concentration of suitable industries - (sugar, food processing, slaughter houses, poultries, dairies etc.) Ground water table close to surface Lack of landfill sites or waste has to be transported over long distances for land filling
A preview of
WTE Technologies
Pyrolysis
Thermal degradation of organic materials through use of indirect, external source of heat Temperatures between 300 to 850oC are maintained for several seconds in the absence of oxygen. Product is char, oil and syngas composed primarily of O2, CO, CO2, CH4 and complex hydrocarbons. Syngas can be utilized for energy production or proportions can be condensed to produce oils and waxes Syngas typically has net calorific value (NCV) of 10 to 20 MJ/Nm Extreme pyrolysis, which leaves only carbon as the residue, is called carbonization. Technically proven at pilot scale but not in commercial scale
Incineration
Controlled combustion of waste with the recovery of heat to produce steam that in turn produces power through steam turbines Combustion temperatures are in excess of 850oC Waste is converted into CO2 and water Any non-combustible materials (inorganic such as metals, glass) remain as a solid, known as bottom ash (used as feedstock in cement and brick manufacturing) Needs high calorific value waste to keep combustion process going, otherwise requires high energy for maintaining high temperatures Commercially applied for over two decades, improved pollution control measures ensure adherence to strict EPA and EU norms.
Types of Incineration
Incineration
Mass burning
Processed Waste combustion (RDF burning)
Several stages of mechanical segregation, size reduction and drying to improve calorific value and achieve uniform sizing Can handle heterogeneous waste Better conversion efficiency Better quality of ash and flue gas
Limited processing to remove noncombustible and oversized items Suitable for source segregated or homogeneous waste
MSW to RDF and Power process - Selco
Gasification
Can be seen as between pyrolysis and combustion (incineration) as it involves partial oxidation. Exothermic process (some heat is required to initialize and sustain the gasification process). Oxygen is added but at low amounts not sufficient for full oxidation and full combustion. Temperatures are above 650oC Main product is syngas, typically has NCV of 4 to 10 MJ/Nm3 Other product is solid residue of non-combustible materials (ash) which contains low level of carbon
Plasma Gasification
Use of electricity passed through graphite or carbon electrodes, with steam and/or oxygen / air injection to produce electrically conducting gas (plasma) Temperatures are above 3000oC Organic materials are converted to syngas composed of H2, CO Inorganic materials are converted to solid slag Syngas can be utilized for energy production or proportions can be condensed to produce oils and waxes
Anaerobic digestion
Suitable for domestic sewage and organic wastes treatment, but not for MSW Biological conversion of biodegradable organic materials in the absence of oxygen at temperatures 55 to 75oC Residue is stabilized organic matter that can be used as soil amendment after proper dewatering Digestion is used primarily to reduce quantity of sludge for disposal / reuse Methane gas generated used for electricity / energy generation or flared
Comparison of Technologies
Use additional document
WTE in Indian Context
The problems
Heterogeneous waste without source segregation High moisture and inert content SWM has not received the required priority Lack of clear guidelines regarding tipping fee to the developer Local government and public institutions lack the financial strength for scientific waste disposal
The opportunities
MSW 2000 rules and supreme court guidelines Increased focus on source segregation and scientific collection High energy prices and demand-supply gap Support from National and State level ministries for renewable energy Increased private sector interest in SWM Acceptability of RDF as a coal-substitute Improvements in the boiler technologies and pollution control technologies
Pointers for the Developers
Proper waste characterization (composition, calorific value, inert percentage etc.) and choice of technology Agreement with municipality for supply of conforming waste (penalty clause for nonconformance) Power purchase agreements using open access system Performance guarantee for key equipments Backward integration into collection and transportation Educate the public on WTE
Future Outlook
Rapid urbanization and increased focus on waste management would create innovative opportunities in the waste management sector, especially waste to energy. All Class I cities would have to go for scientific waste disposal, almost all will be PPP models More zero waste industries or industrial parks Industries going for captive power plants using waste to energy technologies Backward integration by WTE companies thus exercising control on input quality
To know more about how Selco can help with the solid waste management, visit www.selco.co.in
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