Although the amount of municipal solid waste (MSW) is decreasing in Japan, nearly 80% of it has been incinerated. Incineration residue now comprises three quarters of the final waste to be disposed of in landfills. In the stoker incineration facility, for example, incineration residue is composed of grate shift ash, bottom ash, flue gas ash (such as boiler ash), and air pollution control residue. As each ash has different characteristics, it is necessary to control discharge separately from the facility in order to optimize the methods of resource recycling/final disposal suitable to each type. In Japan, approximately one quarter of incineration residue is recycled; the main way to recycle incineration residues currently is by melting and as raw material for cement. In Europe, metal particle recovery facilities from incineration bottom ash are rapidly spreading and in Europe and Taiwan, incineration residues are being recycled into construction materials. Introducing metal particle recovery facilities and applying aging treatments are both advantageous for subsequent cement raw material, construction materials, as well as final disposal. Now, the recycling and disposal of flue gas ash and air pollution control residue are left as our future tasks.

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A trend seen in China recently shows more and more municipal solid waste (MSW) incinerators being constructed and a rapidly increasing amount of MSW undergoing incineration. In 2016, the incinerated MSW reached 73.78million tons/year, which is more than twice that of Japan’s. As for incineration residue, bottom ash is being used as a construction material, however, disposal of fly ash is of concern due to the fact that it is categorized as hazardous waste and the huge amount being generated is estimated to be more than 4.0million tons/year. Heavy metal contents in Chinese fly ash are at the same level as Japan’s. In China, the popular disposal method is sanitary landfilling after stabilization/solidification, however treatment in cement kilns, using high temperature melting and sintering treatments, has also recently begun. Although the criteria for construction materials produced by treatment of fly ash using a cement kiln exists, there are no criteria for construction materials produced by other treatments. In the near future, it will be necessary to establish such criteria, along with the strengthening of legal frameworks and information data bases in order to secure the sustainable management of fly ash in China.

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Recently, although the potential recovery of unused resources from incineration ash has been widely discussed, the source of these unrecovered resources has not yet been adequately studied up to now. In this paper, we discuss the source of gold found in incineration ash using the result of a consumer questionnaire survey on waste generation and its final destination. Among the potential general waste, PCs, game machines, AV equipment and printers are huge potential sources. These are, however, hardly ever treated as combustible wastes and are instead independently treated from other wastes to recover the valuable metals. Therefore, other small but non-negligible wastes should also be used gold sources in incineration ashes, both as combustible wastes and residuals from the pretreatment processes for other type of wastes.

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In order to recover metal elements from municipal waste incineration bottom ash, various analyses were carried out on products obtained from a typical physical sorting flow using an incineration bottom ash generated from the pretreatment kiln of a gasification and melting furnace. We investigated the correlation between concentration behaviors for various elements and made clear the existent state of elements in the feed, characteristics of the products, and the significance of each unit operation in the physical sorting flow involving comminution and separation stages.
We point out that : (1) since the oxidation of metal (especially iron) phases occurred in the kiln, peeling and/or liberation should be achieved by using a specific comminution technique, (2) air tabling was found to be an effective method for concentrating heavy metals, (3) gold followed a similar behavior to copper in the concentration flow, and (4) finer size fractions where oxidized metal phases are concentrated need to be removed in early stages of the flow but precious metals have to be recovered from the size fractions.

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With the ratio of municipal solid waste incineration residue to final disposal sites amounting to 77%, as of FY2008, it is crucial that resource recycling be systematically accelerated. For urban areas in particular, employment of ordinary Portland cement requiring dechlorination for large amounts of municipal solid incineration residue should be considered together with wide-area treatment that incorporates eco-cement requiring the use of up to 50% or more incineration residue for cement raw material. Meanwhile, the use of existing cement factories must also be considered for utilization of molten slag, metal recovery by extraction or physical sorting according to regional characteristics. Presentation of an optimal public system that will be able to contribute to integrated efforts for the environment, the economy, and society as a whole is required.

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In Japan, melting treatment for municipal solid waste has been being conducted within the industry since the year 2000. The Eco-Slag Utilization Promotion Committee was established in order to regulate the Japan Industrial Standard and to promote slag utilization for concrete and road construction material. Today, approximately 800000ton/year of slag are produced and recycled as concrete and road construction materials in compliance with the Japan Industrial Standard. With the aim of expanding its application overall, several uses for eco-slag, including sand-piling, drainage improvement, agricultural utilization and marine blocks, have been developed.

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Many past studies have been conducted to promote effective utilization of municipal solid waste (MSW) insineration residue as construction materials. However, utilization of MSW insineration residue is very limited, compared to other recycled materials such as slag materials and coal ash. This manuscript presents a review of the technical guidelines for other recycled materials, and addresses technical requirements and environmental quality control for the promotion of MSW insineration residue recycling, particularly in geotechnical applications. In addition, case histories on recycling of disaster waste insineration ash implemented after the 2011 Great East Japan Earthquake are summarized, along with mechanical properties of the waste layer at a coastal landfill site mainly containing MSW insineration residue and recycled MSW insineration bottom ash.

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In June 2016, the Tokai-Hokuriku branch of Japan Society of Material Cycles and Waste Management in Iwate Prefecture conducted an on-site inspection tour of three cities that were heavily damaged during the Great East Japan Earthquake of 2011. Although the scenarios and degrees of damage were different in these three cities of Ootsuchi, Yamada and Miyako, a vast amount of valuable information was obtained from the on-site inspection. This article presents a report of what was observed and the on-the-ground reality, while also providing a discussion regarding the various issues associated with the recovery and reconstruction process following the Great East Japan Earthquake disaster. The findings obtained here will be very helpful in preparing for any future earthquake disasters.

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[in Japanese]

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