Current State and Problems in Municipal Solid Waste Treatment Technologies

In fiscal 2000, Japan generated 52.36 million ton of waste, slightly more than the previous year. By source, there were 34.37 million ton of household waste and 17.99 million ton of business waste. Of all waste that was treated, 46.78 million ton went through intermediate treatment whether incineration, crushing or sorting, while 2.22 million ton were directly transported to recyclers, together accounting for 94.1% of all treated waste. Of the 46.78 million ton of intermediate treatment waste, 2.87 million ton were recycled and reused. Of the intermediate treatment waste, 40.35 million ton or 77.4% of the whole were incinerated. The amount of final disposal waste has shown a tendency to decrease at 10.51 million ton in fiscal 2000. The biggest problem of general waste treatment is that it is difficult to find new landfill sites. Because of this, attitudes are moving away from the end-of-the-pipe approach of before and have recently started heading towards emissions control, sophisticated treatment and recycling. Also, because of issues regarding the management of chemical substances such as dioxins and the need to prevent global warming as well as stiffen regulations, constructive efforts, such as the voluntary acquisition of ISO14001, are needed.

1. Incineration Technologies for Municipal Solid Waste
One of the most distinctive features of Japan's municipal solid waste treatment is the comparatively high rate of incineration, now around 77 percent. Waste incinerators can be roughly classified into mechanical stoker types and fluidized bed types, both of which are nearly established technologies. Countermeasures against dioxins - the major problem in waste incineration - are also nearly complete, with the suppression of dioxin generation by high-temperature and efficient combustion and the collection and decomposition of dioxins using decomposing catalyst and bag filters. Regarding the issues of dioxin decomposition, prolonging final disposal sites (detoxifying ashes, recycling) and improving heat recovery, a shift is expected from incineration technologies to new technologies. These will include stoker type incinerators combined with ash solidification technologies, and gasification and ash melting technologies.
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2. Bulky Waste Treatment Technologies The mainstream treatment for noncombustible bulky waste is crushing by means of rotating, impact, then sorting. While sorting allows the recovery of steel and aluminum, prices for these recovered resources fluctuate, depending upon market conditions. Enactment of the Law for Recycling of Specified Kinds of Consumer Electric Goods promotes a great reduction in the amount of bulky waste discharged. The mainstream treatment for combustible bulky waste is shearing and crushing, followed by incineration.
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3. Recyclable Waste Treatment Technologies Technologies for sorting the bottles and cans that are discharged are nearly complete. At present, the main topic is automatic sorting of bottles by color to save labor. Manufacturers have produced a variety of methods on a commercial basis, which are working. But destinations for the recycled glass must still be developed. Also, passage of the Low for Promotion of Sorting and Recycling of Containers and Packaging has stimulated recovery of an increasing amount of PET bottles Technology that provides simple and convenient blowing, pressing and packing for them is expected.
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4. Incineration Residue Melting Technologies This technology melts, detoxifies and recycles incinerator residue. It comes as a fuel-driven system or electric system. Melting reduces incinerator residue into chemically stable slag of 1/3 to 1/2 the original volume. It almost completely breaks down harmful substances found in incinerator residue such as dioxins, renders heavy metals harmless and can thicken and separate low boiling point metals as fly ash. Applications as concrete aggregate and roadbed material have been developed for molten slag, and studies are underway to create Japanese Industrial Standards. Research is also moving ahead on the oxidation and reduction of molten fly ash with the objective of recovering the heavy metal resources contained therein. Some of the technical topics are how to reduce energy consumption rate and how to prolong service-life of refractors. Infrastructure building is a major issue facing the recycling of molten slag and fly ash.
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5. RDF Technologies RDF (refuse-derived fuel) technology is suitable as a countermeasure against dioxins in small-scale waste incinerators. These days it has been diffused as a possible technology for large-area waste treatment as well. More than a dozen RDF plants are now operating in Japan. The refuse-derived fuel is widely used for heating or as a heat source at public facilities. Because it is composed of waste, however, thorough combustion control is essential. The ideal application for this technology is RDF power generation. If power plant location problems can be resolved, it will be possible to apply this technology in each and every prefecture in Japan.
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6. Super Power Generation Technology in Refuse Incinerators Four of these systems, which use waste incineration and gas turbines to generate electric power, are already in operation in the cities of Takasaki, Sakai, Kitakyushu and Chiba, Japan. By taking advantage of the resulting increase in power generating efficiency (from around 15 percent to around 35 percent), the surplus electric power can be sold. Using an emergency gas turbine generator as the combined system generator can also help reduce the relatively high initial costs. The market can be expected to grow now that the Electric Utility Industry Law permits wholesaling and self-transmission of generated power, but the technology is influenced by the unit price of electricity sold.
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- Written by Sanwa Research Institute, supervised by Professor Takashi Gunjima

Waste treatment technologies
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Municipal Solid Waste Treatment Technology Information from Member Corporations