Future Municipal Solid Waste Treatment Technologies

Waste treatment technologies of the future will most likely promote sustainable economic development, particularly in terms of saving resources and energy. They will also contribute to improvement of both social systems and technical development in response to tomorrow's "circulation-type" societies. Recycling, which is economically efficient and based on appropriate waste treatment, will be important, but gradual progress is also expected in reducing waste discharge volumes both at the individual level through lifestyle changes, and at the corporate level through efforts at so-called "zero emission." We will also see increases in material recycling, thermal recycling, appropriate processing of toxic matter, and technologies to preserve life environments. Private sector enterprises such as PFI can also be expected. Following is a short survey of some of the municipal solid waste treatment technologies we can expect to see in the future.

1. Gasification and Ash Melting Technology
This is considered the next-generation waste incineration technology because it simultaneously reduces dioxins, cuts exhaust, melts ash using the energy of the waste itself, and allows material recycling. Systems are roughly classified into kiln, fluidized bed, and shaft incinerator types, and more than a dozen major manufacturers are competing intensely in their development. Several plants with shaft incinerator systems are already in use for incinerating municipal solid waste, and the first kiln type plant is under construction. A number of problem are as have been identified, including the need for stable waste quality, stable control over power generation, and durability of the ash incinerator. These problems notwithstanding, however, widespread use of these systems is possible if their practicality and reliability in actual use can be confirmed.
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2. Thermal Decomposition Technology for Dioxins
Inflammable dechlorination is representative of this technology. In this process the fly ash is heated in a reduction atmosphere, causing a dechlorination reaction that decomposes the dioxins within the fly ash. Around 95 percent to 99 percent of the dioxins are decomposed. Because the equipment is compact and inexpensive, its installation can be expected in both new and existing incinerators.
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3. Technologies for Conversion of Waste Plastics to Oils
This technology, representative of the material recycling technologies, thermally decomposes waste plastics and converts them into oils and gases. Several manufacturers are already operating trial plants. Problems still to be resolved include reducing manufacturing costs, achieving stable residue processing, and developing markets for the resulting product. The Low for Promotion of Sorting and Recycling of Containers and Packaging does not apply to waste plastics until the year 2000. While the effect of this technology on reducing waste is often compared with blast furnace intake and thermal recycling methods, we can expect to see its industrialization.
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4. Pneumatic Transportation of Municipal Solid Waste
This technology, which uses a suction method to transport municipal solid waste, is effective for office buildings or housing complexes in which a public utility conduit has been provided during urban redevelopment. The initial investment is high, but handling is safe and hygienic. Systems of this type are now operating in about 20 buildings, and small-scale systems using vacuum trucks are undergoing trial testing. Cost-performance remains the key factor in gaining widespread use of this technology. The possibility is high for its future use in reducing cleaning costs in large urban redevelopment projects, in buildings such as hotels and hospitals that require a high degree of cleanliness, and in condominiums for the elderly.
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5. Next-Generation Stoker Furnace
A new generation of stoker furnace that is more efficient and causes less environmental load than earlier stoker furnaces has been developed and is in the application stage. The development concepts were (1) to improve combustion efficiency (Low air ratio high temperature combustion), (2) clean and effectively utilize incinerator ash and gas, (3) improve running costs by recovering heat, and (4) ensure stable operation. These concepts and the corresponding technologies are illustrated in Fig. 1.
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- Written by Sanwa Research Institute, supervised by Professor Takashi Gunjima

Figure 1. Concept and Corresponding Technologies of Super Stoker Furnace

The Present Level of Municipal Solid Waste Treatment Technologies
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Future Municipal Solid Waste Treatment Technologies