A sludge recycling and treatment center that makes use of thermophilic methane fermentation from domestic kitchen waste and night soil sludge started operation in Japan in 2000. The characteristics of the raw material (night soil sludge, domestic kitchen waste), the performance of methane fermentation, the effect of recycle flow on the water treatment system and the cogeneration of electric power has been studied by collecting methane fermentation data for two years. During this period, stable methane fermentation performance was achieved. The highest electrical power generation by methane gas was 2, 243 kWh/day. This was equivalent to about 15.3% of the power consumed at the entire sludge treatment plant. Due to the return water flow from the methane fermentation process, the BOD/Kj-N of the activated sludge influent water was lower compared to when there is no recycle flow. Therefore, there was a tendency for the amount of methanol charged into the secondary denitrification tank to increase. However, the cost of this consumed methanol was small compared to the total running costs. Results indicate that is possible to implement a full-scale treatment plant that makes practical use of organic waste.

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In effect since April 2001, Japan's law for recycling specified kinds of home electrical appliances has made the recycling of plastics recovered from waste home electric appliances such as television sets, refrigerators, air-conditioners, and washing-machines an important problem. This paper focuses on pellets recycled from polypropylene (PP) and polystyrene (PS), two plastic resins sorted during recovery processes from waste home electric appliances, and investigates the mechanical properties of each. The results of feasibility studies show that while PP has a good potential for recycling with high strength and flexural modulus, and a good degree of IZOD impact strength, PS does not, making the latter a poor candidate for material recycling. Based on these results, tests were performed on mixed recycling pellets made from differing ratios of virgin-PP blended with recycled-PP. Evaluation and SEM observation of the mechanical properties and microstructure respectively of these mixed plastics suggested PP's relative applicability for material recycling in terms of its recycling capabilities.

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This study was conducted, by using two 3.5m wide large-scale scoop-type Fermentors with the goal of improving the method of forced static aeration in order to aerate garbage equally in a cross section of the fermentor, and thus, ferment the garbage satisfactorily. The experiments were carried out for about 9 days on garbage sediment about 1, 000-1, 600 mm in height under aeration through aerial-pipes on one side wall of the fermentor. Compared to the conventional method, that is, aeration through pores in the bottom plate of the fermentor, changes in temperature, moisture content, pH, and degradation of organic matter in the garbage in a cross section of the fermentor confirmed that there was a difference in the progress of aerobic fermentation depending on whether the source of aeration was one wall side point, the other wall side point, or the center point of the fermentor. These results indicate that the cause is the difference in the apparent density of garbage at the three points of the fermentor, because of frictional force between the wall of the fermentor and the sediment garbage, and so, the amount of aeration turns out to be unequal. The method of aeration was improved by placing covering plates of 750 or 1, 000 mm width over the porous plate along both walls of the fermentor. In consequence, it was confirmed to improve the aerobic fermentation when the width of covering plates was 750 mm and when it was also aerated through the middle 2, 000 mm width of the porous plate. This result indicates that the amount of aeration for garbage at the wall side point, which is of low apparent density, is restricted by the operation of covering plates, and aeration for garbage at the three points of the fermentor becomes equal.

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Understanding the behavior of heavy metals in an ash melting furnace is important to avoid heavy metal contamination in recycled materials and facilitate the metals' effective recovery. The volatilization behavior of heavy metals is strongly related to distribution of molten salts and slag. This study measured distribution ratios of heavy metals for molten salt and slag as (L_M= (mass%M) salt/ (mass%M) slag, M=Pb, Zn) using a hermetic or open cell. Heavy metals were vaporized with an almost fixed distribution between molten salt and slag. Distribution ratios of Pb and Zn decreased with increased basicity of slag. The chlorinated reaction of Pb and Zn by CaCl₂ can explain the mechanism of this effect. Total chlorine content in slag increased with increased basicity of slag. This fact is attributable to the exchange reaction between chlorine ion in molten salt and oxygen ion in slag.

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A technique for inspecting the deterioration of plastics has been developed to enable the plastic chassis (ABS copolymer and high-impact polystyrene) of office automation appliances to be reclaimed. First, infrared spectra of degraded plastic samples were measured with a Fourier transform infrared spectrometer using the attenuated total reflection method. The ratio of C=O bond peak intensity to benzene ring peak intensity was found to correlate with the deterioration depth from the surface. This ratio was defined to be the degree of deterioration. Next, the strength of the samples of reclaimed plastic was tested, and it was found that the Izod impact value decreased as the blending ratio of degraded plastic increased. Equations determining conditions for classifying degraded plastic were derived using the relationship between degree of deterioration and deterioration depth, and between Izod impact value of reclaimed plastic and the blending ratio of degraded plastic. An example of classification condition was calculated using these equations. Three classifications were made for molding of blending virgin material, sandwich molding and thermal recycling. Finally, a plastic deterioration inspection appliance was produced and used to inspect the chassis of used personal computers. The results showed that the increase in the degree of deterioration with a number of years of use was greater for ABS copolymer than for high-impact polystyrene.

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The purpose of this analysis was to show the quantitative relation of the recoverable amount of recyclable waste and domestic refuse generated from households. Continuous actual survey data was collected from questionnaires and waste generation measurements. In this paper, we made an analysis on the differences of the recoverable amount of recyclable waste for papers and plastics, and the effects of waste reduction.
Firstly, we examined the change in the total amount of waste generated between each survey period, and we classified the data into three groups taking into consideration the difference in this amount. Secondly, we defined the ratio R/D to be that of the recoverable amount of recyclable waste to domestic refuse generated from a household. We examined the data for composition of refuse, and showed the difference in the recoverable amount for each type of composition. Thirdly, in order to show the variations in the recoverable amount of papers and plastics, we conducted a comparative analysis between one group of “top quartile” and another of “others” for the ratio R/D. Lastly, we showed the quantitative relation of the recoverable amount of recyclables and domestic refuse. Here it was revealed that there were definite differences.

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“Recycle markets” have been carried out at many universities, but due to the large number of prevention factors that continue to exist, the markets have been discontinued. The recycle market at Hiroshima University was stopped in 2000. After analyzing past data, results showed that the continuation of recycle markets were not feasible due to human conditions, such as staff numbers being insufficient; this was due to an increase in “physical exhaustion” and “mental stress” with a decrease in the “feeling of satisfaction and achievement.” Three main problems had to be tackled in order to change the situation, so a campaign was developed in order to: 1) Recruit a robust volunteer staff; 2) Welcome and manage visitors; and 3) Create a new purpose by showing that participation is a positive contribution, and the recycle market at Hiroshima University was restarted in 2001. Sustainable management of the recycle market was possible when these three factors were taken into consideration and tackled. The new-spirited Hiroshima University example can definitely be followed in order to continue markets at other universities too.

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The scallop mid gut gland (MGG) is known as a waste product that contains much cadmium, a toxic heavy metal. With the aim of establishing an optimum de-cadmium process in MGG incineration, this study seeks basic data for showing guidelines. Experimental examination was carried out on cadmium emission behavior and the removal of cadmium vapor from exhaust gas. Kaolinite particles were utilized as a sorbent. Results showed that cadmium in MGG started emission to exhaust gas at temperatures higher than 600°C. The whole quantity volatilizes under an 850°C oxygen lean combustion condition. The organic volatile matter included in MGG inhibited cadmium capture by the kaolinite particle. In addition, cadmium capture performance by the kaolinite particle was compared for packed bed and fluidized bed conditions. Greatest cadmium capture efficiency of 80% was obtained under a fluidized bed condition with a sample from which we had removed organic volatile matter ex ante.

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Extraction equilibria of palladium (II) from acidic chloride media were studied at 303 K to examine the potential use of three kinds of xanthine derivatives (=RN), caffeine, theophylline, and theobromine, as selective extractants. Xanthine derivatives have exhibited high selectivity for palladium (II) over copper (II) and platinum (IV) . The extraction reaction of palladium (II) was elucidated by examining effects of hydrochloric acid, chloride ion, hydrogen ion, and extractant concentration as PdCl₂+2RN ⇔ PdCl₂ (RN) ₂ for caffeine, theophylline, and theobromine derivatives Using the xanthine derivatives, palladium (II) was extracted selectively from mixtures containing the 25-fold amounts of copper (II) or platinum (IV) . In addition, it was easy to strip the palladium (II) extracted with the xanthine derivatives using an ammonia or thiourea solution.The stripping percentage of palladium (II) was more than 60% using single batchwise processing.

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The enactment of a new law in April 2001 requiring the recycling of home electric appliances (televisions (TV), refrigerators, air-conditioners, washing-machines etc.) has made the recycling of waste plastics discharged from disposable home electric appliances an important issue in Japan. Since many of the plastics used in the back-cabinets of television sets (TVBC) contain flame retardant agents, it has been pointed out that such recycling may present difficulties.
In this research, special attention has been paid to TVBCs made of polystyrene resin (PS-TVBC) . These were collected for recycling at the home electric appliances recycling factory (HEARF), where they were processed into recycling pellets, and their basic mechanical properties closely monitored.
Results showed that the resin pellets reproduced from PS-TVBC possessed good basic mechanical properties. It follows that if the suitable sorting recovery of PS-TVBC is carried out at HEARF, material recycling of PS-TVBC should be fully possible. It is moreover possible that a high level of material recycling in the loop from TV to TV may also be achieved.

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