According to Waste Management Hierarchy, Waste prevention is the top. As the preferred option, it is followed by re-use and recycling, recovery including energy recovery, and safe disposal as a last resort. Incineration is part of the recovery, including the energy recovery category, and is thus a factor of an integrated waste management system and not a standalone component.
Incineration is a waste treatment process that involves the combustion of organic substances contained in waste materials. Incineration itself is commonly only one part of a complex waste treatment system that altogether provides for the overall management of the broad range of refuse that society produces. Like all waste treatment methods, incineration aims to reduce waste volume and hazards, while collecting (and thus concentrating) or destroying potentially harmful substances. Through incineration, waste mass reduction can range from 75 to 80 percent, while waste volume can be reduced by 85 to 90 percent depending on its composition. Incineration processes can also provide a means to enable recovery of the energy, as well as the mineral and/or chemical content from waste by producing electricity and/or thermal energy.
Waste generally consists of organic substances, minerals, metals and water. During waste incineration, oxidation of the combustible materials occurs when they have reached the necessary ignition temperature and come into contact with oxygen, producing flue-gases while simultaneously releasing energy. The non-combustible materials (e.g. metals, glass) remain as a solid, known as Bottom Ash, which contains a small amount of residual carbon. The flue gases produced carry residues from incomplete combustion and a wide range of pollutants, and thus they are transferred to Air Pollution Control (APC) for cleaning. The bottom ash produced can either be landfilled or utilized. The legislation and boundary conditions regarding the utilization of bottom ash appear to vary in different countries.
Waste and its management are a significant environmental issue. The thermal treatment of waste may therefore be seen as a response to the environmental threats posed by poorly managed or unmanaged waste streams. Incineration aims at providing an overall reduction in the environmental impact that might otherwise result from waste. However, during operation some potential environmental consequences are encountered, which are related to process residue production, fugitive emissions, mainly from waste storage, raw material (reagent) consumption, and overall process emissions into air and water (including odour). The enforcement and application of modern emission standards, and the use of state of the art pollution control technologies, has resulted in air emissions reduction to a level where pollution risks from waste incinerators are now generally considered to be very low.
Apart from the its role in ensuring effective treatment of otherwise potentially polluting unmanaged waste, Waste to Energy Treatment Plants can have a particular role in energy recovery by exploiting the energy value of the waste, as it can provide district heating.
Waste combustion is particularly popular in countries such as Japan where land is a scarce resource, and developed economies such as Denmark and Sweden. In the year 2005, it was estimated that 4.8 percent of the electricity consumed by the Danish nation was produced by incineration and the amount of heat was some 13.7 percent of the total.
MSW incineration is an advanced waste treatment technology which is costly to implement, operate, and maintain. In order for an incinerator to be economically feasible, costs must be minimized through waste tipping fees and energy sales. So it is of primary concern to know the end use of the energy produced: district heating, steam, electricity, or any combination, as well as to have guaranteed waste volumes and price over the lifetime of the facility, in order to be financially sustainable.
The energy generation potential is related to the quality and quantity of the input waste. Thus, the nature of the waste and its calorific value are factors of the utmost importance for the feasibility of an MSW incineration plant.
The WtE Consultant is a unique tool that conducts preliminary calculations on the main operational characteristics of a MSW incineration facility, from the waste heating values, the facility’s energy production and environmental emissions, to a preparatory techno-economic feasibility investment study. The tool aims to give rough estimations of the operational and economic characteristics of a MSW incineration facility.
It should be taken into account that waste generation, composition and energy demands are closely related to socio-economic conditions and the degree of urbanization and industrialization, so data cannot be projected from one place to another. However in the WtE Consulting tool geographical, economic, population and technical (thermodynamic steam characteristics, etc) parameters have been taken into account. For feasibility assessment, preliminary and comprehensive studies should be conducted. Comprehensive assessment should involve comprehensive collection of local data on waste generation and composition, a detailed study of plant finance and a full environmental impact assessment.
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