Material flow in Japan as a recycling society has been analyzed. Input resources entering Japanese society is calculated to be 2,050 Mts/y, are potentially recyclable resources for industry is 410 Mts/y, and the maximum amount of recyclable materials is calculated to be 216 Mts/y, taking into account loss by usage. Fundamental equations which describe the material flow in a recycling society and E_r (recycling ratio of materials), E_rr (amplified ratio of recycling), and E_w (reduction ratio of waste materials) should be taken into consideration to decide the construction of a recycling society. Taking steel flow as an example, We studied the present state of recycling, its relationship with harmful substances, the problem of natural and man-made resources and the treatment of "stocks" in material flow. We conclude that there is little chance of constructing the recycling society in Japan if the current mass flow continues in future.

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Poisonous substances that contaminate recycling materials are classified into two categories. One includes is poisons to the living body, such as lead and arsenic, carcinogens and endocrine disruptors, pathogenic germs and prion. The other includes poisons to materials for industrial use such as Cu in Fe and Ni in Cu for metals, and poisons generated in during use and different kinds of polymers for plastics. The poisonous substances can be eliminated by waste treatment or through natural circumstances. However, such poisonous substances recycle and accumulate to a higher level in a recycling than in a non-recycling society. The concentration of Cu, which is a poison for steel, increases with the passage of time and becomes higher by recycling, thereby influencing the recycling system itself. The characteristics of plastic, inorganic glass and industrial products are discussed from the same point of view.

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At present, the Japanese government is promoting the construction of bigger incineration plants for urban refuse treatment to prevent a pollution by dioxins etc. Plant makers are also investing in technical research and development. In practice, however, the pertormance of plants is not always satisfactory, because the altered propertise and reduced quantities of refuse resulting from the strict selection of materials for recycling do not match the optimal values in the plant design. This report describes the system analysis by computer simulation for evaluation of the process system, and a discussion of refuse incineration and ash melting to slag through the experiences of plant operation in provincial cities.

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This paper describes the decomposition pathway of methyl mercaptan (MM), a the typical malodorant, and sulfur balance during its decomposition in two systems: (i) an ultraviolet (UV) lamp system and (ii) a sheet material with titanium dioxide supported on fiber activated carbon with UVirradiation (FAC/TiO₂ sheet) system. The observed MM removal rates were found to be higher in the FAC/TiO₂ sheet system than the UV lamp system. As decomposition products of MM, dimethyl disulfide, carbon disulfide, sulfur dioxide, methane sulfonic acid, and sulfuric acid were detected in the FAC/TiO₂ sheet system, while the same five compounds and hydrogen sulfide were produced in the UV lamp system. These compounds accounted for the sulfur balances in the FAC/TiO₂ sheet and the UV lamp systems at 50–79% and 100%, respectively. Finally, the obtained results allowed us to propose MM decomposition pathways in both systems.

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Decomposition of low concentrations of covalent chlorides and fluorides (CCl₄, SF₆, CHF₃, CHClF₂) in N₂ by non-thermal plasma was investigated. Specifically, the influence of hydrogen and of in-situ Ca(OH)₂ absorbent on the decomposition were determined in terms of the decomposition ratio of the gases, which form inorganic halide from free halide species. It was found that the decomposition ratios of SF₆ and CCl₄ with 2% H₂ in N₂ were higher than those in N₂ atmosphere. HCl, Cl₂, HF and F₂ were regarded as the major products formed from the decomposition of the gases in N₂ atmosphere. With the combination of non-thermal plasma and in-situ absorption using a layer of Ca(OH)₂ coated on the surface of the grounding electrode, the decomposition ratio increased and products such as HCl, Cl₂, HF and F₂ were effectively scavenged. It was demonstrated that the Ca(OH)₂ absorbent played an effective role in capturing the unwanted intermediates in the plasma reactor.

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The effects of the amount of adsorbed trichloroethylene (TCE) and temperature on the photocatalytic decomposition of TCE in an oxygen-based gas were investigated using TiO₂ catalyst supported on silica gel beads (TiO₂/SiO₂ bead catalyst). Experiments were carried out in the temperature range of 303–353 K and TCE concentration range of 50–500 ppm. The effects were evaluated quantitatively in terms of the decomposition ratio of TCE, defined by the ratio of the decomposed TCE amount to the adsorbed TCE amount, and the fractions of CO₂ and HCI products in the decomposed TCE.
From the dependence of the TCE photocatalytic decomposition on the initial amount of adsorbed TCE at a constant temperature of 303 K, the optimum amount of adsorbed TCE on the TiO₂/SiO₂ catalyst for effective decomposition was found to be 8.0–15 mmol. In this range, the decomposition ratio of TCE, and the fractions of HCl and CO₂ were respectively about 85, 70 and 60 %. As for the effects of reaction temperature on the photocatalytic decomposition, the decomposition ratio of TCE was independent of temperature within experimental error, but the fractions of CO₂ and HCI in the decomposed TCE increased as temperature decreased.

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Innovative semiconductor processes using microwave-excited high-density plasma equipment have been proposed. The feature of these processes is the use of Kr for one of the process gases. Kr is very expensive because the atmosphere contains Kr at only 1.14 ppm by volume. Therefore, it is necessary to recover and reuse Kr from exhaust gas containing about 50% N₂ and about 50% Kr.
Isotherms and self-diffusivities for adsorption of N₂ and Kr were measured on commercial active carbons and zeolites. It was found that active carbons and Na-A zeolite exhibited thermodynamic and kinetic selectivity, respectively. Kr recovery equipment comprising an equilibrium based separation process (PSA I ) and kinetically controlled separation process (PSA II) has been developed. The equipment was able to produce Kr with 99.5% recovery and at a purity of 99.99%. Kr reuse can be achieved by additional use of a purifier.

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Iron oxide-carbon composite catalysts were prepared for dechlorination of chlorinated organic compounds included in fuel oil obtained from waste plastic. The optimum preparation method was established based on measurements of initiol activities in the catalytic decomposition of chlorocyclohexane in a pulse-type catalytic reactor. Moreover, in the dechlorination of chlorocyclohexane and the fuel oil obtained from waste plastic in a flow-type catalytic reactor, a high rate of dechlorination was found to be maintained for at least 5–6 h.

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Detoxification of polychlorinated biphenyls (PCBs) is accelerating globally. when PCBs in alkaline 2-propanol are irradiated with ultraviolet (UV) rays, they are reduced to biphenyl, and sodium chloride (NaCl), acetone and H20 are generated as by-products.
But in UV irradiating process, when dechlorination of PCB progresses, PCB decomposition rate is reduced because of biphenyl decomposition and generating many derivatives.
Therefore, we have developed a hybrid method using UV-irradiation and a noble-metal catalyst which can dechlorinate PCBs in the presence of biphenyl. By this method, the concentration of PCBs is decreased below 10 ppb, and both NaCl and biphenyl can be recovered as by-products. In addition, the UV/Catalyst method is environmentally sound, because organic chlorine compounds such as PCDDs, PCDFs, Co-PCBs and OH-PCBs are decomposed to below detectable level.

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Decomposition of epoxy resin was carried out with sub and supercritical water in the temperature range of 300–450° C. At 350–380° C and 25 MPa, about 90% of the resin was decomposed to water+ methanol-soluble components, including low molecular weight products and monocyclic phenol compounds such as phenol and iso-propylphenol. Water in the reactor was found to inhibit the coking and enhance the decomposition of the resin, compared with the case of pyrolysis, in which the yield of THF -soluble components of high molecular weight exceeded 50%. Using supercritical methanol, the epoxy resin was partly decomposed, but the yield of products of low molecular weight was lower than that using supercritical water. Carbon fiber reinforced plastic (CFRP), which is composed of carbon fiber and epoxy resin matrix, was treated with supercritical water at 380° C and 25 MPa to examine the industrial applicability of this method. As a result, clean carbon fiber was recovered and the resin was decomposed and removed from the carbon fiber.

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Wet oxidation of 100 ppm aqueous solution of o-chlorophenol was performed in a batch reactor at 373, 413 and 433 K under 0.1 MPa oxygen pressure. The effects of an alkaline reagent (NaOH) and a catalyst (3% Ru/TiO₂) on the decomposition of o-chlorophenol were investigated.
The reaction time needed to attain 100% decomposition of o-chlorophenol at lower temperature was reduced by the addition of the alkaline reagent or Ru/TiO₂ catalyst. The alkaline reagent played an important role in dechlorination of o-chlorophenol, resulting in the formation of organic acids (acetic and formic acids) and the generation of chlorine ion (HCl) through catechol as intermediate, but the complete decomposition of o-chlorophenol to inorganic compounds was not achieved. With the Ru/TiO₂ catalyst, on the other hand, the main final products were inorganic compounds and chlorine ion, formed via p-chlorohydroquinone and organic acids as intermediates.

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Mechanochemical (MC) treatment using calcium oxide (CaO) is one of the new technologies applicable for decomposition of dioxins contaminating fly ashes. This study was aimed to reveal their decomposition pathways in the MC treatment using 4-chlorobiphenyl (4CB) as a model compound of co-PCBs, one of the dioxin families.
Ion chromatography showed that the MC treatment caused dechlorination of 4CB in a final ratio of 100%. The finding that the chlorine balance during the MC treatment was accounted for chlorine ion and chlorine contained in the remaining 4CB indicated that the first step of 4CB decomposition in the MC treatment was dechlorination. Biphenyl, cyclohexyl benzene, and ter/quaterphenyls were identified as the main products of 4CB decomposition by a GC-MS analysis, while MC treatment of biphenyl and cyclohexyl benzene yields ter/quaterphenyls and bicyclohexyl, respectively. In addition, MC treatment of p-terphenyl confirmed benzene ring cleavage, i.e., 4-penthyl biphenyl and isopropyl biphenyl were detected as p-terphenyl decomposition products. These results suggested that 4CB decomposition progresses via dechlorination/hydrogenate-reduction or dechlorination/polymerization, and benzene ring cleavage.

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We investigated the possibility of preparing composite particles composed from expanded polystyrene (EPS) and inorganic solid powders by using semi-chemical recycle method with the limonene/ethylene glycol emulsion.
In the experiment, magnetite and titanium dioxide were added as solid powders.
As a result, it was found that composite particles coated with two solid powders were able to be prepared. Moreover, the adhesion rates of both solid powders were found to be maximum at pH=7 of the continuous phase. From these results, it was suggested that the more valuable composite materials could be prepared by the lower environmental load process.

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This study aims to establish an in-situ cadmium removal method in high temperature combustion or gasification conditions for industrial waste including cadmium compounds. As a mineral sorbent to capture the metallic cadmium and the cadmium chloride, kaolinite was found to have the highest performance. The adsorption mechanism by which kaolinite captures cadmium chloride at high temperature was then experimentally elucidated. The results suggest that the adsorbed cadmium could not be desorbed, but rather that it combined more strongly with the kaolinite with increasing retention time. The amount of cadmium captured by the kaolinite is significantly dependent on the moisture concentration in the reaction system, and its minimum concentration depends on the molar ratio of cadmium to kaolinite. The results suggest that the presence of above 1 mole of moisture enhances the removal efficiency, promoting stoichimetric removal reaction in which 1 mole of kaolinite captures 1 mole of cadmium chloride.

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The removal of lead in fly ash from municpal waste incineration by the solvothermal reaction and the utilization of the fly ash by solvothermal hot-press treatment were studied. This process involves both high-temperature and high-pressure aqueous treatment of the fly ash in order to accelerate metal hydrolysis as a result of the increased ion product constant of water.
Under solvothermal conditions of 473 K temperature and 20 MPa pressure, 19% of lead in the fly ash was removed a 60-min reaction. On the other hand, under alkali solvothermal conditions created by adding 1.5 mol/l of NaOH.
The solvothermal hot press at the conditions of 20 MPa pressure and 523 K temperature for 60 min treatment resulted the product having 40 MPa compression strength, 7 MPa tensile strength and 22 HR 15W Rockwell hardness. Furthermore, by mixing fly ash with glass at a 50% ratio, the compression strength, tensile strength and Rockwell hardness of the product increased to 80 MPa, 13 MPa, 80 HR 15W, respectively. The values of these physical properties are comparable to those of mortar cement, artificial aggregates and artificial lightweight aggregates.
These results demonstrate, the applicability of the solvothermal treatment to stabilization and utilization of the incineration fly ash.

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A new process to fix anthropogenic carbon dioxide via treatment of waste concrete was proposed. The main reaction of the process is the extraction of calcium ions from waste concrete particles by use of pressurized carbon dioxide (several MPa in pressure). The extracted Ca²⁺ is deposited as calcium carbonate (CaCO3) particles when the pressure is reduced to the atmospheric pressure. The CaCO3 particles can either be disposed of directly or reused industrially for cement production. The former case is a direct disposal of CO₂; the latter case is an indirect disposal of CO₂, because the net mining amount of virgin limestone could be reduced. Energy consumption and cost for the fixation process of CO₂ emitted from a 100-MW thermal power plant by the proposed process was evaluated based on laboratory-scale experimental results. It was found that energy consumption for the operation was 3.5 MW per 100-MW power generation, and the fixation cost was about JPY 2100 per metricton of carbon. This result indicates that the present process is highly competitive with the previous CO₂ fixation scenarios such as ocean sequestration.

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The effect of activated carbon (AC) injection on control of mercury emission from a fluidized bed type municipal solid waste incinerator (FB-MSWI) was investigated in two actual FB-MSWIs. Furthermore, lab-scale experiments were conducted to confirm the results of the field tests. In the field tests, Hg concentration at the outlet of the bag filter was reduced to less than 0.002 mg/m³N by injecting AC of 50 mg/m³N. In the lab-scale experiments, The Hg reduction ratio of fly ash with activated carbon was 50 % higher than that of fly ash without activated carbon. No difference in Hgreduction ratio was found between AC concentrations of 50 mg/m³N, and 100 mg/m³N. With FB-MSWI fly ash, it was easier to remove mercuric chloride than metallic mercury. This characteristic of FB-MSWI fly ash was different from that of stoker type MSWI fly ash. This difference was estimated to be caused by the composition of fly ash, especially the contents of copper and iron.

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A new process to prepare activated coke from organic wastes such as mixtures of waste wood and waste plastics has been investigated. The process consists of pre-carbonization of organic wastes, a wet -briquette forming of the pre-carbonized product and carbonization of the briquette to produce activated coke. The activated coke prepared was found to have a sufficientry high mechanical strength and relative surface area for applycation as an absorbents in a moving bed type gas purification plant (i.e., purification plant for exhaust gas from sintering machine). The gas evolved in the pre-carbonization was also found to have a high caloric value and can be used for a heat source for the process.
This study examined the effects of process variables such as carbonization temperature, time and the raw materials on the yield and on the properties of activated coke.
In the pre-carbonization of mixtures of waste wood and waste plastics at weight ratios from 100/0 to 60/40, the yield of coke was found to remain constant. To explain this phenomenon, a co-carbonization mechanism of cracking materials from waste plastics on the surface of carbonized waste wood was proposed.

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Since composting is the decomposition process of organic materials by microorganisms, the quality and the quantity of odor emissions should be influenced by the types of microorganisms which decompose the organic materials. This study, examined the effect of seeding on the emission of ammonia, one of the most troublesome components of the odor produced by composting. When three different commercially available seeds were tested for composting the time courses of organic matter decomposition and ammonia emission differed among them, but the quantities of ammonia emitted were simlar when the same quantity of organic material was decomposed and no remarkable difference in the effect of ammonia reduction was found among them. A thermophilic bacterium, Bacillus licheniformis DO1, was then obtained from compost as a potentially effective thermophilic microorganism for reduction of ammonia emissions during composting, which grew on protein-contaning medium without greatly increasing the medium pH. When this strain was used as a seed for composting at the optimum temperature of 50° C, ammonia emissions were reduced to about 40% of those observed with the commercially available seeds.

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For the stabilization and reduction of the excess activated sludge produced in a small-scale wastewater treatment plant, an aerobic digestion process is considered to be more suitable than an anaerobic one. In this paper, batch aerobic digestion experiments with and without pH adjustment to 7 were investigated using acclimated sludge, which was acclimated to synthetic wastewater (substrates: glucose and peptone), and excess activated sludge, which was taken from a municipal wastewater treatment plant.
The pH adjustment did not greatly affect the final ratio and the rate of decomposition of the sludge solids. The final decomposition ratio of the excess activated sludge was smaller than that of the acclimated sludge, but the decomposition rate of the excess activated sludge was larger than that of the acclimated sludge. The accumulated amount [mol] of NaOH applied in order to adjust pH to 7 was almost equal to the amount of sludge decomposition [mol-C₅H₇NO₂], and it was confirmed that the aerobic digestion cccurred according to the predicted reaction. Therefore, the degree of sludge biomass decomposition can be estimated from the amount of applied alkali chemicals. Since the pH adjustment to 7 promotes the nitrifying reaction, NH₄-N is rapidly oxidized to NO₃-N, and very little NH₄-N remaines in the liquid phase. The phosphorus concentration of the liquid also decreased, because the orthophosphate dissolved into the liquid phase from biomass is precipitated as an apatite by the pH adjustment to 7. The production of hydragen sulfide gas in the decomposition of the sludge, was determined by the under of days before the darkening of lead acetate paper. It was faund that the production of the gas was delayed when pH was adjusted to 7, and that the adjustment repudly stabiliged the digested sludge.

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Freezing-thawing dehydration by centrifugation was applied for the reduction of food waste (kitchen refuse). Impedance analysis showed that plant cell membranes were severely disrupted by freezing-thawing so that plant tissue was easily dehydrated by this treatment. Freezing-thawing dehydration was also effective for gel materials, such as soyprotein curd, through freeze -denaturation but was not effective for animal tissue and cheese. The present method was applied to ten food materials to obtain about 50% reduction in weights suggesting its effectiveness for transportation, incineration, and composting of food waste.

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This study aimed develop a method of effective use of shochu distillation remnants. We examined inhibitory effects of shochu distillation remnants on the growth of various tumor cells in vitro and toxicity to normal rats in vivo. High inhibitory effects of shochu distillation remnants on the growth of stomach tumor cells were obtained. Furthermore, shochu distillation remnants showed no toxicity to normal rats in vivo. The presence of sugar components in the shochu distillation remnants was suggested by IR spectra and HPLC analysis. These results suggest that shochu distillation remnants might be effectively used not only as medicine but also as food supplements.

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H₂ production from organic wastes and metal wastes by absorbing CO₂ during pyrolysis and gasification (HyPr-RING method) was studied experimentally. Experiments were performed by using an autoclave at 973 K and 25 MPa.
From organic wastes, such as wood, salad oil, styrene foam, PET bottles, black rubber, benzene, graphite, sewage sludge and polyvinyl chloride, it was found that H₂ was the major product gas, while the remainder was CH₄. CO₂ was completely absorbed by the sorbent of Ca(OH)₂. CO was not detected in the product gas. These wastes had high conversion to gas phase, except styrene form, benzene and graphite.
Only 40 ppm NH₃ was detected in the product gas of the sewage sludge. Others harmful gases, such as NO_x, HCN, H₂S and HCl were not detected in the product gases of sewage sludge and polyvinyl chloride.
Powders of Al and Fe could be completely converted to H2 by reaction with H₂O. However, with increasing sample size, the conversion of Fe fell rapidly.
H₂ production from mixtures of organic and metal wastes was also confirmed by experiment.

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A cylindrical liquid bridge under zero-gravity becomes unstable when its length exceeds its circumference (the Rayleigh-Plateau limit). The behavior of a liquid bridge stabilized by axial electric fields was investigated using the drop-shaft of the Japan Microgravity Center (JAMIC).
It was confirmed that AC electric fields in air stabilized an almost cylindrical liquid bridge whose length was above the Rayleigh-Plateau limit for a short period under microgravity, and that the unstable liquid bridge under microgravity broke asymmetrically in the axial direction.

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External catalytic packed-bed palladium membrane reactors with baffle rings were made to reduce radial gradients of concentrations and temperature. The effect of baffle rings was experimentally tested and compared with the simulated results. The leakage of gas between the baffle ring and the outer tube caused the decrease of the effectiveness of baffle rings. Improved palladium membrane reactors with baffle rings were proposed to prevent the leakage of gas.

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The dispersibility of rare earth oxide particles, such as La₂O₃, Ce₂O₃ and Y₂O₃, in various solvents was evaluated. From the results, the relationship between the dispersibility and Hansen's solubility parameters (δ _d, δ _p, and δ _h) of the solvents was investigated. To represent the dispersibility of particles in various solvents, the median diameters of the particles in the solvents were measured. The values of Hansen's solubility parameters of a hypothetical solvent producing optimal dispersion were estimated from the measured results. From the results, the dependence of estimated δ _p values on dielectric constant of the particles and dependence of estimated δ _h on isoelectric point of the particles were investigated.
The dispersibility of rare earth oxide particles in various solvents can be evaluated by using the percentage contribution of Hansen's solubility parameters (f_d, f_p and f_h) in triangular charts. From the measured result, Hansen's solubility parameters of the hypothetical solvent producing the optimal dispersion of particles can be determined. These Hansen's solubility parameters of the hypothetical solvent differ according to the kind of particle. The δ _p and δ _h values of the hypothetical solvent producing the optimal dispersion of particles are reasonably correlated with the dielectric constant and isoelectric point of the particles, respectively.

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The effects of the number of discs and the operating conditions on the separation performance of an oil-water separator with conical discs were examined. The estimated value of the partial separation efficiency obtained under the assumption of a plug flow model was compared with the measured value. The difference between the two values was decrease with the number of discs and increase with the inlet flow rate of the separator. The estimated overall removal efficiency of oil, which was calculated on the basis of the estimated partial separation efficiency and the measured size distribution oil droplets of was up to 25% higher than the measured value.

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To examine the applicability of the circulating moving bed process to CO₂ recovery, the performance of the system was evaluated by installingin a coal-thermal power plant, a test unit is capable of processing 50 m³/h of real flue gas.
The circulating moving bed process for CO₂ recovery consists of a adsorption tower, a regeneration tower and other devices. The flue gas is fed continuously into the adsorption tower, where CO₂ is adsorbed onto the packed adsorbent. The adsorbent saturated with CO₂ is fed into the regeneration tower, where CO₂ is recovered by heating/depressurizing, and the regenerated adsorbent is circulated back to the adsorption tower. The demonstration test confirmed that the process could recover highly pure CO₂ with low energy consumption. The performance of the process was stable for about 8,500 h. And the process was operated continuously for 520 h. It was confirmed that the system was capable of recovering 90% of CO₂ with 99% purity. This leads to the conclusion that the moving bed process is suitable for recovering CO₂ from the flue gas. The electrical consumption and heat consumption were 263 kWh/t-C0₂ and 3.66× 10⁶ kJ/t-CO₂, respectively. The refrigerator and flue gas blower in the process consumed the major portion of electrical energy, while the thermal energy was mainly consumed in the regeneration tower. The circulating moving bed process can be operated without countermeasures for material corrosion because the entice system is dry. The process is durable and easy in maintenance. Because zeolite is harmless, the process is superior to the conventional wet scrubbing with respect to safety and environmental impacts.

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To reduce the product cost of CWM (Coal Water Mixture), CWM was produced using brown coal, that had been upgraded into oil. CWM produced from the upgraded Roy-Yang coal pulverized by the conventional wet ball mill method had a low coal particle content of 49 wt%. To increase the coal content of CWM, the rounding method was applied, and the coal particle content of CWM was there by increased to 57 wt%. Based on these results, it may be concluded that the rounding method is effective for reducing the product cost of CWM.

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