Agenda - Council - 08/26/1980 - Laserfiche WebLink

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MECHANICAL SEPARATION (HIGH-TECHNOLOGY METHODS) What role should mechanical separation strategies play within a comprehensive solid waste management plan? Contrary to the low-tec~nology source separation of recyclable mate- rials, off-site separation methods most often utilize highTtechnotogy or mechanized systems. There are many existing'mechanical separation methods, including air classification, magnetic separation, screen- ing, inertial separation, flotation, optical sorting and electro- static separation. These~technologies are made to handle large volumes of wastes and are often located near a disposal or other processing facility. As with source separation programs, the major controlling factor for the operation of mechanical separation systems' is the necessity of having markets for the recovered materials. INCINERATION WITH ENERGY RECOVERY On what basis should th_~e public decide to choose incineration with energy recovery as an abatement strategy as opposed to waste separation and biological recovery? Incineration with energy recovery can take several forms, including waterwall combustion, dedicated boilers, refuse-derived fuels (RDF), modular incineration and pyrolysis. The recovered energy can be used to produce electricity, heat buildings or drive manufacturing pro- cesses. These operations are more costly than disposal in landfills, and require locations that optimize the use of energy recovered. Waterwall combustion systems burn solid wastes with little or no waste processing or materials recovery. This type of furnace is preferred in the large-scale burning of solid waste because of the relative ease of maintenance and high efficiency in heat transfer (usually 50-60 percent). Usually electrostatic precipitators are used to control air pollution emissions. Tubes within the boiler walls contain circulating water that recovers the heat to produce steam. An important determinant of steam price is whether the steam can be supplied continuously. If not', the steam can be sold only to users that already possess steam producing capabilities, or to others who must build standby, systems to ensure steady production. Often economic incentives, such as reduced price compared to fossil fuel, must be offered to firms to purchase the steam. RDF systems use municipal solid waste to produce a transportable alternative fuel for use in conventional fossil-fuel-fired energy systems. Often the waste is processed to separate metals and glass from the combustibles to increase the Btu value of the RDF. Revenues from the sale of RDF will depend upon the Btu content of the RDF, the price of fossil fuel currently being used (most often coal), and the degree of modification necessary for the energy user to convert the existing system to burn RDF.