Gas permeability and tortuosity for packed layers of processed municipal solid wastes and incinerator residue.

To make a proper evaluation of gas component movement inside a landfill site, it is important to investigate the different parameters related to gas flow. In this work gas-filled porosity, intrinsic permeability, tortuosity and equivalent pore radius were determined for various packed wastes, such as incineration ash, shredded bulky waste and shredded incombustible waste. These parameters were measured/inferred for samples packed in a column and exposed to a controlled gas flow. The effect of waste conditions, especially the moisture content, on these parameters was also investigated. The intrinsic permeability of such packed wastes was generally in the order of 10(-10) to 10(-9) m2, except for some ash that was one to two orders lower. The tortuosity of waste layer was greater than that of a particulate material and ranged between 2 and 10. The equivalent pore radius was generally in the order of 10(-4) m, which means that gas diffusion is still ordinary in such packed waste layer. The obtained results will be utilized when simulating gas flow inside a landfill site for biogas extraction or site aeration.     

Supercritical methanol for polyethylene terephthalate depolymerization: observation using simulator

To apply PET depolymerization in supercritical methanol to commercial recycling, the benefits of supercritical methanol usage in PET depolymerization was investigated from the viewpoint of the reaction rate and energy demands. PET was depolymerized in a batch reactor at 573 K in supercritical methanol under 14.7 MPa and in vapor methanol under 0.98 MPa in our previous work. The main products of both reactions were the PET monomers of dimethyl terephthalate (DMT) and ethylene glycol (EG). The rate of PET depolymerization in supercritical methanol was faster than that of PET depolymerization in vapor methanol. This indicates supercritical fluid is beneficial in reducing reaction time without the use of a catalyst. We depicted the simple process flow of PET depolymerization in supercritical methanol and in vapor methanol, and by simulation evaluated the total heat demand of each process. In this simulation, bis-hydroxyethyl terephthalate (BHET) was used as a model component of PET. The total heat demand of PET depolymerization in supercritical methanol was 2.35 x 10(6)kJ/kmol Produced-DMT. That of PET depolymerization in vapor methanol was 2.84 x 10(6)kJ/kmol Produced-DMT. The smaller total heat demand of PET depolymerization in supercritical methanol clearly reveals the advantage of using supercritical fluid in terms of energy savings.     

Projections of industrial water withdrawal under shared socioeconomic pathways and climate mitigation scenarios

We estimated global future industrial water withdrawal (IWW) by considering socioeconomic driving forces, climate mitigation, and technological improvements, and by using the output of the Asia–Pacific Integrated Model/Computable General Equilibrium (AIM/CGE) model. We carried out this estimation in three steps. First, we developed a sector- and region-specific regression model for IWW. The model utilized and analyzed cross-country panel data using historical statistics of IWW for 10 sectors and 42 countries. Second, we estimated historical IWW by applying a regression model. Third, we projected future IWW from the output of AIM/CGE. For future projections, we considered and included multiple socioeconomic assumptions, namely different shared socioeconomic pathways (SSPs) with and without climate mitigation policy. In all of the baseline scenarios, IWW was projected to increase throughout the twenty-first century, but growth through the latter half of the century is likely to be modest mainly due to the effects of decreased water use intensity. The projections for global total IWW ranged from 461 to 1,560 km³/year in 2050 and from 196 to 1,463 km³/year in 2100. The effects of climate mitigation on IWW were both negative and positive, depending on the SSPs. We attributed differences among scenarios to the balance between the choices of carbon capture and storage (CCS) and renewable energy. A smaller share of CCS was accompanied by a larger share of non-thermal renewable energy, which requires a smaller amount of water withdrawal per unit of energy production. Renewable energy is, therefore, less water intensive than thermal power with CCS with regard to decarbonizing the power system.     

Compartment model of aerobic and anaerobic biodegradation in a municipal solid waste landfill

The mathematical formulations in a one-dimensional compartment model of the biodegradation of organic landfill components are described. The model is designed to switch between anaerobic and aerobic conditions, depending on the local oxygen concentration. The model also includes the effect of environmental factors, such as moisture content, pH, and temperature, on reaction rates. The model includes not only biodegradation processes for carbon compounds (acetate, CO2, CH4), but also for nitrogen compounds involved in nitrification and denitrification due to their significance in landfills. Two example runs to simulate anaerobic and aerobic waste were conducted for a single landfill unit cell by changing the organic content and diffusion coefficient.     

Recovery of solid fuel from municipal solid waste by hydrothermal treatment using subcritical water

Hydrothermal treatments using subcritical water (HTSW) such as that at 234 °C and 3 MPa (LT condition) and 295 °C and 8 MPa (HT condition) were investigated to recover solid fuel from municipal solid waste (MSW). Printing paper, dog food (DF), wooden chopsticks, and mixed plastic film and sheets of polyethylene, polypropylene, and polystyrene were prepared as model MSW components, in which polyvinylchloride (PVC) powder and sodium chloride were used to simulate Cl sources.While more than 75% of carbon in paper, DF, and wood was recovered as char under both LT and HT conditions, plastics did not degrade under either LT or HT conditions. The heating value (HV) of obtained char was 13,886-27,544 kJ/kg and was comparable to that of brown coal and lignite. Higher formation of fixed carbon and greater oxygen dissociation during HTSW were thought to improve the HV of char.Cl atoms added as PVC powder and sodium chloride to raw material remained in char after HTSW. However, most Cl originating from PVC was found to converse into soluble Cl compounds during HTSW under the HT condition and could be removed by washing.From these results, the merit of HTSW as a method of recovering solid fuel from MSW is considered to produce char with minimal carbon loss without a drying process prior to HTSW. In addition, Cl originating from PVC decomposes into soluble Cl compound under the HT condition. The combination of HTSW under the HT condition and char washing might improve the quality of char as alternative fuel.     

Remigration and growth of loggerhead turtles (<Emphasis Type="Italic">Caretta caretta</Emphasis>) nesting on Senri Beach in Minabe,Japan: life-history polymorphism in a sea turtle population

There are size-related differences in the use of feeding habitats (planktonic or benthic; oceanic or neritic) by adult female loggerhead sea turtles (Caretta caretta) within Japanese populations. We thus hypothesized that the differences may be reflected in their remigration and growth patterns, and investigated the relationships between body size and remigration intervals, growth rates, and remigration percentages, for female loggerheads nesting on a Japanese beach between 1991 and 2001. Although remigration intervals, growth rates, and remigration percentages were not significantly different among females, there were trends for longer remigration intervals and lower remigration percentages in smaller females. All females grew little. Considering these results along with previous findings, we speculated on the life-history strategy of female Japanese loggerheads.Communicated by T. Ikeda, Hakodate