The Basic Law for Establishing the Recycling-based Society was enacted, and the importance of recycling has become more widely recognized. However, environmental pollution from toxic substances in recycled materials is a concern that prevents some recycling. This paper compared environmental safety management systems for recycled materials in Japan, the Netherlands and Germany, specifically for building materials used in general environment. In result, we clarified eight issues which should be considered for future management systems: (1) consistency among the managements for non-recycled materials, recycled materials and wastes, (2) distribution management and utilization management, (3) informative management, (4) phased management according to hazard level, (5) consistency with soil environment management, (6) consideration of use situations, (7) types of classification values to use, and (8) practical management. We proposed a new framework that takes these issues into account.

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Large amounts of wastes containing higher levels of calcium have been generated from the byproducts marine and livestock industries, i.e., shells, eggshells, and bones. Chemical and energy industries generate waste CO in a process of coke formation and waste NH₃ in the hydrodenitrogenation of coals and petroleum. If CaCN₂ can be formed from these wastes, the process could contribute to the reduction of solid wastes. With this point in mind, CaCN₂ formation from shells, eggshells, and chicken bones was studied using pure NH₃ and CO. About 18-20 wt% CaCN₂ was formed from both kinds of shells through reaction with NH₃ and CO at 600°C for 6-10 h and about 8 wt% from chicken bones under the same conditions.
It was estimated from the balance of gaseous compounds that the major reaction is 6 CaO+6 NH₃+6 CO→4 CaCO₃+2 CaCN₂+9 H₂+N₂.

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The de novo formation of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) caused by the interaction between fly ash and flue gas was investigated. In these experiments, flue gas from the laboratory-scale fluidized-bed incinerator was passed through an electrically heated flow reactor in which fly ash obtained at the same laboratory-scale incinerator has been filled. The results show that PCDD/Fs formed in where large amount of fly ash has been deposited by the internal force and thermo-phoresis. In the case of the de novo formation, PCDDs/DFs concentration is proportional to the HCl concentration in the flue gas. It is also noted that PCDDs/DFs are not formed at the temperatures around 200°C but significant PCDDs/DFs formation was observed at around 300°C and also that Cu content in the fly ash at the level of 10wt% strongly promote PCDDs/DFs formation at not only 300°C but also 200°C.

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The influence of the sludge ratio on the high-solids thermophilic methane fermentation of the organic fraction of municipal solid waste (MSW) and bio-sludge was investigated by using a semicontinuous flow completely mixed reactor. The methane fermentation experiments were conducted at a constant influent total solid (TS) concentration of 12-13% and a constant retention time of 15 days by altering the sludge ratio from 0% to 50% under thermophilic condition (55°C) . As the sludge ratio in the influent TS increased from 0% to 50%, the degradation efficiency of volatile solid decreased from 78% to 49%, while the biogas production yield decreased from 0.8 to 0.5 L/g-VS. For maintaining high rate stable methane fermentation, addition of minerals to the feed was necessary for the MSW-rich cases when the sludge ratio in the influent TS was lower than 10%, while successful operation was possible without mineral addition when the sludge ratio was higher than 25%. The energy production in an integrated biogas system of thermophilic methane fermentation and power generation using biogas was calculated based on the experimental results obtained from this study.

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Carbonized panels were prepared from waste phenol-formaldehyde resin and magazine paper by gas phase activation method. The bending properties and porous structure of these carbonized panels were investigated. The modules of elasticity (MOE) was increased with carbonization for raw panels. However, the MOE and modules of rupture (MOR) were decreased with carbon dioxide gas activation. Thus, decomposition of organic substance including waste phenol-formaldehyde resin through the carbon dioxide activation process influenced the decrease of MOE and MOR. The specific surface area of carbonized panel containing waste phenol resin was 650 760 m²/g and suggesting that carbonized panels has a well-developed porous structure.

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For the purpose of weight and volume reduction and recycling of solid waste with high water content, drying experiments were carried out with a combustion gas thermal jet dryer. Dehydrated cake of sewage sludge, bean curd refuse and dehydrated cake of waste water sludge from a dye works were used for drying experiments. The experimental parameters were temperature and the flow rate of thermal jet and the feed rate of samples. The thermal efficiency and volumetric heat transfer coefficient of the dryer were calculated to investigate the drying characteristics of the samples. The following results were obtained. (1) Drying performance of this machine depends much more on the disintegration characteristics than on the drying characteristics of the samples. (2) The highest value of volumetric heat transfer coefficient of the dryer was 4, 000 kcal/h⋅m³⋅°C. (3) The actual effective particle diameter of the dried product and average residence time of particles in the processing chamber were larger than the theoretical values by two orders, a result probably caused by the large number of collisions between particles. (4) There was a limited to the feed rate giving a good disintegration process. Increasing feed rate over this value decreased the drying performance.

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