There are a number of studies that state the advantages of incorporating a deposit-refund system, which is one of the economic instruments sometimes used in waste management structures. According to previous studies, however, there have also been negative effects seen in the deposit-refund system, which is why these systems have rarely been successfully put into practice. This paper attempts to clarify the origin of the gap between recommendations made by previous studies and the difficulties found in applying the system for real-life applications. The paper organizes the advantages and disadvantages found in previous economic studies on deposit-refund systems. In conclusion, it suggests that further studies are necessary for fully understanding cost-benefit analysis of the deposit-refund system, taking into consideration both the advantages and disadvantages. It also suggests the need for finding solutions regarding the elimination of these disadvantages in the deposit-refund system so that the advantages can be better utilized.

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Decomposition of methyl bromide (CH₃Br) and bromobenzene (C₆H₅Br) was investigated along with Br sorption from CH₃Br or C₆H₅Br by Na₂CO₃ sorbent.
Under a CH₃Br-N₂ atmosphere without Na₂CO₃, results showed that HBr and C₂H₂ were generated by thermal decomposition of CH₃Br at temperatures greater than 673K. Similarly, under C₆H₅Br-N₂ atmosphere without Na₂CO₃, both HBr and C₆H₆ were generated at temperatures higher than 673K.
The presence of Na₂CO₃ sorbent was found to promote decomposition of CH₃Br and C₆H₅Br at temperatures of 673-973K. During CH₃Br and C₆H₅Br decomposition in the presence of Na₂CO₃, the formation of NaBr was observed. It was therefore concluded that Br gaseous compounds formed by the decomposition of CH₃Br and C₆H₅Br were absorbed on Na₂CO₃. Regarding the Br absorption ratio on Na₂CO₃ sorbent at a temperature of 873K, the Br absorption ratios on Na₂CO₃ under CH₃Br-N₂ and C₆H₅Br-N₂ atmospheres were, respectively, 0.50 and 0.29.

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A start-up procedure for mesophilic methane fermentation digestion from dairy cattle manure without inoculum was investigated using a laboratory-scale continuously-stirred tank reactor. The reactor was first operated in batch mode by diluting the cattle manure to TS 1.5%. Gas production greatly increased from day 17 to 22 and then decreased. VFA first increased and reached a peak on day 22, then gradually decreased. After 37 days of batch mode operation, the reactor was changed to continuous mode operation, and the HRT was shortened in increments from 100 days to 50 days, and then to 30 days on day 70. The start-up period consists of two characteristic phases. In the first phase, VFA accumulation was observed because the methane production rate was low. In the second phase, rapid VFA degradation with an increase in methane production was observed. Microbial community shift during the start-up period was monitored using molecular techniques. Results of clone library analysis suggest that during self-digestion, Methanosarcina grew gradually and became predominant at day 30, though they were not detected at the beginning. Population dynamics of the archaeal community were investigated with real-time PCR. During the transition from the first phase to the second phase, the digester showed significant increase in the Methanosarcina rRNA gene. The population of Methanosarcina correlates with the biogas production rate. A start-up method by self-digestion of dairy cattle manure was established in this research.

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Heat accumulation will often occur in storage piles of waste and recycled products, such as Biomass Fuel and Refuse-Derived Fuel (RDF), leading to serious fire hazards. For example, the fire and explosion at a RDF power plant storage tank in Mie Prefecture killed two fire fighters in August 2003. In order to prevent fire from breaking out at waste storage and stockpile areas, heat generation and the accumulation mechanism of stored waste were investigated using calorimetric and chemiluminescence (CL) studies. As measurement samples, RDF and model materials for RDF such as polypropylene, were used. Primary heat generation and a heat accumulation were evaluated using certain calorimeters. In a range from room temperature to 80°C, RDF has very slow heat generation with water and oxygen, and this heating reaction causes the RDF temperature to rise over 80°C. In the range from 80°C and above, the oxidation reaction accelerates the heat accumulation of RDF, eventually creating a run-away reaction that can cause self-ignition. Oxidation in the low-temperature region was also evaluated using a CL analyzer. This experimental data shows that RDF contains some organic peroxides, and these initiate an auto-oxidation reaction in the low-temperature region.

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Methane gas yields and production processes were studied in laboratory experiments on the codigestion of cattle manure with organic cosubstrates using digesters with an effective volume of 6 liters maintained at a mesophilic temperature of 37°C and with a hydraulic retention times of 30 days. Butter, breadcrumbs and protein supplements were used as cosubstrates. We found that lipids, carbohydrates and proteins contribute differently when used as cosubstrates for cattle manure digestion. The maximum loading rates of the cosubstrates before they inhibit methanogenesis were 2.2gVS/L per day for breadcrumbs, 2.4gVS/L per day for butter and 0.8gVS/L per day for protein. We measured methane gas (CH₄) yields per amount of volatile solids (VS) for each cosubstrate. Butter showed the highest yield (0.82L/gVS_lipid at 68 percent concentration). The yield of breadcrumbs was second highest (0.42L/gVS_carbo at 57 percent). Protein yield ranked third (0.31L/gVS_protein at 64 percent) and was only 54 percent of the theoretical methane yield of protein. NH₄-N generated by protein codigestion seemed to inhibit methanogenesis even at low loading rates.

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The aim of this study is to evaluate the material balance in a novel recycling process for production of poly-L-lactic acid (PLLA) from municipal food waste, and the possibility of recycling the byproduct as compost fertilizer. This process yielded approximately 7kg of PLLA from 100kg of food waste, which means that 33% of the total carbon in the food waste was recovered as PLLA. As a major byproduct, about 29% of the dry matter in the food waste was obtained as saccharified residue. This fraction showed a similar C/N ratio as food waste, while its electric conductivity and oil content were relatively low. Through successive high-temperature and aerobic treatment, the saccharified residue was converted into stable organic compost that could be used as a delayed-release nitrogen fertilizer for the growth of Komatsuna (Brassica rapa var. peruviridis). Moreover, in rice cultivation in paddy fields, the saccharified residue compost enhanced crop yield more effectively than chemical fertilizer. These results indicated the possibility of establishing a comprehensive system for recycling municipal food waste into PLLA plastic and nitrogen fertilizer.

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We applied DME (dimethyl ether)-based dewatering technology, which has been developed for high-moisture coal, to dewatered sewage sludge and successfully decreased the water content of sewage sludge from 78wt% to 30wt%. Moreover, we clarified that five minutes is enough to dewater sewage sludge as contact time. In addition, the dried sewage sludge was deodorized. Since the temperature of sewage water is approximately constant throughout the year, sewage water and air can be used as sources of heat for the evaporation and condensation of DME. Thus, DME-based dewatering technology can be thought of not only as a dewatering technology but also as a technology for recovery of heat from sewage water.

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In Japan, there is a large amount of insulating oil that contains traces of polychlorinated biphenyls (PCBs) in transformers, capacitors and other electrical equipment, and these PCBs need to be destroyed appropriately and economically. In this study, we conducted experiments on destroying trace PCBs in oil through incineration in a small furnace at relatively low temperatures between 700 and 950 degrees Celsius in order to examine the possibility of destroying them at ordinary industrial waste incineration facilities.
As a result, we found that the presence of hydrocarbons affects the destruction of trace PCBs much more than the temperature or gas residence time in the furnace. Incinerating with hydrocarbons at a temperature of over 800 degrees Celsius and a residence time of over 2 seconds, traces of PCBs contained in oil can be destroyed with a very high destruction efficiency of over 99.9999%, reducing the concentration in the incineration gas to much lower than the threshold values for industrial hygiene and environmental air quality in Japan. From these results, we believe that traces of PCBs contained in oil can be adequately destroyed by incineration in ordinary industrial waste incineration facilities because a large amount of hydrocarbons surely coexist (in the form of oil) with the traces of PCBs.

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