The condition for material recycling in our country is gradually improving. However, even the current recycling rate of base metals easier to process than rare metals, is not enough. Though several suggestions have been made to improve this situation, they could not be implemented due to restrictions caused by the legal context such as the Waste Disposal Law. Also, in many cases, recycling of materials was limited due to its high treatment costs. If this situation continues to prevail, valuable metal resources indispensable for advanced technology will be lost permanently. And the toxic metals associated with valuable metals will pollute our country gradually. In order to improve the recycling rate and to prevent the diffusion of contaminants, we propose a new system taking various aspects of metal recycling into consideration. This system is based on the concept of "artificial mineral deposit". This system is a paradigm change on the way we look at waste products, as the stockpiled recycling metal is treated as ore deposit. The new system will allow various possibilities of further metal recycling and reduce environmental impact tremendously.

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Extension tests on Shirahama sandstone (blocks I and II) and Shikotsu welded tuff were carried out under confining pressure. Tensile strength increased and then decreased for Shirahama sandstone block I and Shikotsu welded tuff. It decreased or unaffected with confining pressure for Shirahama sandstone block II. Absolute value of lateral strain at peak load point increased with confining pressure and that in uniaxial compression tests distributed in the similar manner on the confining pressure-strain value plot. Absolute value of axial strain at peak load point increased with confining pressure except for Shirahama sandstone block I. 50% tangent Young's modulus increased with confining pressure and that in uniaxial compression tests distributed in a similar manner on the confining pressure-Young's modulus plot. Effect of confining pressure on Poisson's ratio was unclear. Residual strength decreased with confining pressure except for Shirahama sandstone block I. Results of Brazilian tests distribute upper limit of results in extension test under confining pressure on the confining pressure-tensile strength plot except Shirahama sandstone block II which distributed above the extension test results. The effect of confining pressure on tensile strength was roughly explained by assuming a number of discontinuities whose strength was represented by Coulomb criterion and whose angle was different with each other.

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Accurate determination of rock stresses at great depth is one of the most important subjects that should be resolved in the fields such as deep geological disposal of nuclear fuel waste and underground sequestration of carbon dioxide. To determine complete three-dimensional in situ stress at great depth with a high accuracy, the Downward Compact Conical-ended Borehole Overcoring (DCCBO) technique, which is one of stress relief methods, was developed. DCCBO technique can be applied to a water-filled vertical/sub-vertical borehole. The main features of this technique are as follows:
1) This technique is applicable to a water-filled borehole by using an appropriate adhesive.
2) A diving-bell-type bonding device keeps a strain cell dry until the moment of installation.
3) Just before the strain cell reaches the bottom of the borehole, high-pressure nitrogen gas cleans the borehole bottom, where cuttings may exist.
4) The process described above proceeds within a PQ bit which overcores the strain cell.
5) The data during the overcoring is recorded by a multi-channel data logger which is installed at the top of the strain cell.
6) A system consisting of a small video camera and compass for single shots measure the direction of the strain cell.
In laboratory test, a measuring system consisting of a bonding device, a cleaning system and a multi-channel data logger were verified to work well in a water-filled borehole with cuttings on the bottom. Reasonable results were able to be obtained by measurement sensitivity test using a specimen of rock block. Thus, we confirmed the usability of DCCBO technique.

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Removal of arsenite and arsenate in sulfuric acid solutions were investigated with PbS, ZnS, FeS and CuS at 298K. Both arsenic species were removed by PbS, ZnS and FeS. Especially, PbS was most effective to remove arsenic species from the solutions. The removal of the arsenic species by PbS depends on the sulfuric acid concentration and is minimum at sulfuric acid concentrations around 0.01 kmol m^-3. Thermodynamic analysis of the experimental results and XRD and SEM-EDX analysis of the solid residue suggest that the removal of the arsenic species by PbS is due to both arsenic adsorption on PbS surface and precipitation of As₂S_3(am) by the reaction of the arsenic species and H₂S generated by PbS.

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We have already developed the new recycling system for high-water content mud by using paper debris and powder polymer. The modified soils produced by this method have several features such as high failure strength, high failure strain and high durability for drying and wetting. These features are due to the existence of the fibers in the modified soils.
By the way, the amount of paper debris which is necessary in this method depends on the water content, and if the water content is very high, a huge amount of paper debris is necessary to modify the high water content mud. As the cost of paper debris is strongly affected by the fluctuation of the market price, the stabilization and reduction of the processing cost will be possible if the amount of paper debris is reduced. Therefore, in this study, the possibility to use the paper sludge which is discharged in the recycling process of used paper as a substitute for paper debris was investigated.
It was confirmed through the drying and wetting tests that paper sludge can be used as a substitute for paper debris because the modified soils by use of paper sludge showed high durability for drying and wetting. However, the strength of the modified soils by use of paper sludge was not high enough. Therefore, the modified soils by use of paper sludge and paper debris were made, and the strength property of them was examined. In results, when the paper debris of 30kg/m³ was added in the high water content mud, enough strength was obtained. This addition rate of paper debris was approximately half of the one in the previous method without using the paper sludge. Furthermore, it was found that powder polymer and chemical flocculants do not affect the durability and strength of the modified soils. Therefore, it was confirmed that about 75% cost reduction is possible if the paper sludge is used and powder polymer and chemical flocculants are not used.

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Waste plastics are defined as one of organic wastes. According to an official report, the annual total discharge of the waste plastics in Japan shows more than 5 million tons in 2002. Organic waste utilization technology should be developed to decrease of waste plastics, because the landfill cannot be accepted for the industrial waste any more. In order to obtain porous carbonized materials from waste plastics, waste phenol resin was selected to suitable for making carbonized materials.
The purpose of this study is to develop the activated carbon from waste phenol resin and reuse it for functional carbon resources.
The structure of carbonized waste phenol resin was analyzed with gas adsorption measuring apparatus. The results show that the specific surface area of carbonized materials showed more than 900m²/g, when they were carbonized at the lower temperature of 600°C for 10 minutes in N₂ and activated at 1000°C for 120 minutes in CO₂.
Moreover, activated reaction for waste phenol resin were investigated at the carbonization temperature of 800°C for 60 minutes in N₂ and activation temperature of 1000°C in CO₂ by using Ca(OH)₂ as catalyst. The specific surface area of carbonized materials mixed with Ca(OH)₂ after activated at 1000°c for 10 minutes showed about 500m²/g. This value was corresponded to nearly five times of non catalysts at same condition. Therefore, it was confirmed that the Ca(OH)₂ could be advanced the activated reaction for carbonized waste phenol resin.

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Sewage sludge is one of industrial wasts, and the production rate of the sludge is increasing every year. Many municipalities are dependent on incineration, smelting or landfill to reduce sewage sludge. However, landfill cannot accept the sewage sludge any more. Valid processes of sewage sludge are expected to decrease environmental risks and to increase the recycling rate of it. In order to solve these problems, carbonization process has been proposed.
The purpose of this paper is to evaluate the functions of carbonized tablets made from sewage sludge as biomass, humidity control materials, and artificial soil of roof top greening. The chaff, of which sizes are 0.180mm to 0.212mm and 0.212mm to 0.355mm, and zeolite were used as moisture control materials for sewage sludge. The thermal properties of the carbonized sludge were analyzed with TG (thermogravimetry), DTA (differential thermal analysis), DSC (differential scanning calorimetry), and calorimeter. Heating value, or the calorific power, of the tablets, which were carbonized at the temperature of 300°C for 25minutes with the chaff of the sizes of 0.212mm to 0.355mm and 0.180mm to 0.212mm, was approximately 11.9kJ/g to 11.3kJ/g. It corresponds to nearly 80 % of that of chaff, so we conducted a combustion test with the tablets.
The porous carbonized tablets are expected to function as humidity control materials for under floor of building and superior artificial soil of roof top greening. The vegetation monitoring tests of grass were investigated for a period of 120 days with carbonized tablets, zeolite, and charcoal. Moreover, for confirming the environmental risks of the tablets a leaching test of harmful substances from them was studied. The results showed that the concentration of heavy metal contaminant such as Pb, Cd could be controlled below the values of permitted loads.

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