Changing the high-temperature and high-pressure water conditions can significantly affect the physical properties of water. Therefore, application of the high-temperature and high-pressure water technologies attracts attention in various fields in recent years. The following are some researches in our group that have been carried out as the fundamental technologies to establish the sustainable recycling society: (1) Recovery of rare earth metals from waste vehicle-converter catalyst; (2) Recovery of carbon fibers by regenerating from fiber reinforced resins; (3) Recovery of fibers from natural waste materials; (4) Elimination of hazardous ash waste from aluminum and its conversion into recyclable resource; (5) Recycling treatment of waste sand mold from metal casting; (6) Conversion of poly-lactate into value-added material.

Organic wastes have become an important issue in the world, and consequently, the recycling and reutilization of these wastes have drawn increased attention of many environmentalists. As Japanese food waste recycle law has been enforced as a new policy to promote the recycling of food waste, recycling of food waste into liquid animal feeding has been given a priority over recycling for other uses. Technologies which would treat these wastes or even recover some useful organic materials before disposal are of significant importance. One of the possible techniques for the treatment of organic wastes is the use of hydrothermal reaction. The hydrothermal reaction is a promising method for amino acids production and preparation of animal liquid feed from various organic wastes. The liquid feeding has many advantages over dry animal feed, such as control of a respiratory disease, cheaper feeds, automating of feeding system, reduction of the energy consumption. Our studies showed that liquid feed produced by hydrothermal reaction provided a better digestion for animals (high digestibility). The decomposition of organic wastes had produced value-added compounds of organic and amino acids that could be used for animal liquid feeding. Furthermore, we have also proposed a scenario to design a resource recycling network system based on our developed liquid feeding technology to enhance the formation of society in organic resources recycling.

Increased awareness of the environmental, health and safety issues in the use of organic solvents has triggered the studies of supercritical fluid extraction. Supercritical fluid extraction using carbon dioxide as a solvent is a green technology and offers numerous advantages for analytical purpose, mainly rapidity and low organic solvent volume usage. We have been developing a new application of supercritical carbon dioxide extraction on the determination of microbial community structure for environmental assessment. Four lipid biomarkers including respiratory quinones (RQ), phospholipid fatty acids (PLFA), phospholipid ether lipids (PLEL), and polyhydroxyalkanoates (PHA) have been investigated. The studies showed the potential application of supercritical carbon dioxide extraction as a routine method for the comprehensive analysis of microbial community structures in environmental assessment using the lipid biomarkers profile. The developed method have been applied to various environmental samples from anaerobic digestion, wastewater treatment, and composting process. These methodologies could open the road to a superior method for analyzing microbial lipid biomarkers comprehensively for environmental assessment and monitoring, with the possibility of extended application and automation. We also propose a next generation microbial bio-indicator indices to evaluate microbial community structure.