According to our analysis in Osaka and Neyagawa City (both of which have separate collection systems for plastic containers and packaging, and have no designated garbage bag system), 72-74% of the plastic shopping bags found in household waste are reused for waste containment. The remaining 26-28% are disposed of as empty bags. The bags that are taken out every week (mother bags) contain even smaller plastic bags within them. The smaller bags (child bags) are used to hold smaller amounts of waste and are placed in a‘mother bag’for collection. Sometimes child bags contain other bags (grandchild bags), which may even contain more bags (great-grandchild bags), etc. In cities where collection of plastic containers and packaging takes place, 12-14% of all plastic shopping bags in household waste were those that had been reused as mother bags. Of 19 mother bags examined, the average mother bag contained 4.2 child bags, 1.1 grandchild bags, and 0.2 great-grandchild bags. 66% of these minor bags were found to hold wet kitchen waste. From these results, it was estimated that the weight of plastic shopping bags in our household waste could be reduced by 53% if their use was discouraged altogether or if bags made of thinner plastic film were used instead.

View full abstract

Concentrations of nitrogen compounds and organic matters such as BOD and COD substances in a pretreatment pond tend to increase at the later stages of land reclamation in sea-based solid waste disposal sites. For this reason carefully planning is required for land reclamation with wastes. Relationships between monthly amount of disposed materials and the behavior of BOD and nitrogen concentrations were analyzed and parameters concerning elution and decomposition were determined. Using acquired coefficient values, continuous reclamation and intermittent reclamation models were simulated and the intermittent reclamation model was proven to be effective in controlling BOD and total nitrogen concentrations.

View full abstract

Consideration of 3 R (Reduce, Reuse, Recycle) is strongly required for industrial products' design. General-purpose pumps' design makes them difficult to disassemble and classify into single material. Their value-adding functions continue to improve through increased quality, reduced costs, unification of multiple functions, adoption of bond connection methods, built-in compression, and so on. Such features make disassembly difficult.
We developed and manufactured an environmentally friendly general-purpose pump to improve the problems cited above. We specifically improved the disassembly property of the motor, which includes useful, resource-rich parts, and introduction of the concept of“Up-Grading”products, which can realize up-grading of its structure during the use stage. Our assessment method shows that this pump has a 36% lower environmental load than the former product.

View full abstract

The Basic Plan for Promotion of a Recycle-oriented Society proposes as its national goal to reduce the amounts of landfill waste in half by the year 2010. In order to achieve this goal, it will be necessary to understand what types of waste are effective in reducing the amount, and how the reduction can be achieved. In this study, a questionnaire survey among municipalities was conducted to better understand the current state of directly landfilled and incombustible waste. Areas which were checked include types of waste, treatment methods, and the quantities being disposed of.
Results showed that: 1) Ceramic, glass, and metal waste are collected as incombustible waste by over 65% of the municipalities; 2) Incombustible waste is shredded and sorted in almost 40% of the municipalities, while direct landfilling has been adopted by about 30% of the municipalities; 3) Using cluster analysis, municipalities were categorized into 5 groups based on their incombustible waste items. It was found that in one group, collecting only small incombustible items, the quantity of collected and landfilled waste amounts were almost half that of other groups; and 4) Even if a municipality collects various incombustible waste items, 60-80% of the waste quantity could be reducible using shredding and sorting treatment.

View full abstract

With a view to contributing to the evaluation and development of policies regarding the recent trend toward an increasing international movement of waste for recycling, this study reviewed various principles relating to this phenomenon and analyzed the relationships among them. Some areas that were examined were support for the Ban Amendment of the Basel Convention, the urging of caution regarding this, the idea of as ‘global material circulation for recycling’ in a globalizing economy, as well as the implications of Extended Producer Responsibility (EPR) .
Principles for and against the Ban Amendment were found to conflict with each other, as the former places emphasis on ‘prevention’ of wastes while the latter focuses on its ‘recycling’ . The concept of global material circulation will not solve this conflict as it is also aimed at recycling. If a certain international movement, in accordance with the EPR principle, held prevention as its effect, it could provide some positive change in this conflict, but the possible effects require further study. The international movement of goods falling under hazardous wastes, therefore, should continue to be restricted to the extent possible, and further studies on related areas such as possible prevention effects of international movement should be conducted.

View full abstract

Understanding of the inefficiency of waste transportation is needed in order to take substantial measures necessary to establish material recovery systems for demolition and construction wastes over a wide area. We made a flow model that can estimate flows of such wastes between cities and towns. This model uses an algorithm based on the assumption that waste flow is controlled by spatial distribution factors, including the amount of waste discharged, the intermediate treatment capacity and the road distance between two points in the Kanto region. In addition, we developed spatial and quantitative indicators of regional waste imbalances caused by facility distribution. We suggest ways to apply these indicators to decision-making processes from the perspectives of material recovery promotion and improper waste disposal prevention.

View full abstract

Used printed circuit boards (UPCB) contain Cu, Au, Ag, Pd and other valuable metals, as well as elements such as Cu, Cr, Pb and Br that are harmful to the environment. Metal recovery from UPCBs is therefore important to protect the environment and to utilize secondary resources. In this research, the materials from the UPCB of a discarded personal computer were examined. After the UPCB was cut into 20 mm square pieces, it was heated at 873 K to remove resins such as C, H and N. After heating, the UPCB was crushed by a ball mill and the milled powder was separated by sieving. The crushed UPCB (over 250μm) were sorted into magnetic and nonmagnetic particles by magnetic force. Since the fine powder (under 250μm) contained 39 mass % of C, it was heated to 1273 K in an atmosphere of 95% Ar + 5 % O₂, The powder was heated again to 1773 K in an atmosphere of 97% Ar + 3 % H₂. As a result, the slag and metal were separated, and 80% of the valuable metals in the UPCB were recovered.

View full abstract

In this study, we estimated the national potential of biomass/waste resources using statistics, and then analyzed the relationship between population size and potential mass in a community/person for each biomass item. It was found that for agricultural, forestal, and livestock biomass, the potential mass per person (kg/person/year) and accumulated mass for a certain population size (ton/year) were inversely proportional to the decrease in population size. On the other hand, for waste biomass (i. e. food waste, waste paper, sewage sludge), those quantities were directly proportional to the increase in population size.
We then conducted a case study of food waste treatment to compare GHG emissions (kg-CO₂eq/ ton-waste) for four different scenarios including the utilization of biogas with Fuel-Cell, for two model areas (rural/urban) . It was revealed that biogasification followed by the generation of electricity with biogas emitted less CO₂ than when incineration and composting was performed for generation of electricity by FC, which has a greater effect on CO₂ reduction in comparison to that of a gas engine. The difference in parameter settings between rural and urban areas causes a significant impact on GHG emissions, especially for incineration and composting.

View full abstract