Fly ash generated from MSW ash-melting and gasification-melting plants, known as Melting Furnace Fly Ash (MFA), is a valuable resource due to the high content of Lead and Zinc in MFA. This study aimed to find the optimal solvent washing method to remove chlorine, the major contaminant for the refinery process. Four kinds of solvent were used in this study : distilled water, sodium carbonate (Na₂CO₃), sodium sulfate (Na₂SO₄), and distilled water with CO₂ bubbling. After solvent concentration, gas flow rate, number of washings, temperature and washing time were determined, twenty-three MFA from different facilities were washed using each solvent.
Na₂CO₃ showed the highest removal rate of chlorine because it can dissolve Friedel's salt and chloride compound with zinc or lead. Chlorine which could not be removed by Na₂CO₃ washing correlated well with the amount of silicon in MFA. Chlorine contents in the residues obtained by Na₂CO₃ washing were lower than acceptable criteria for Imperial Smelting Process (ISP). In addition, Zinc contents in the residues were higher than the expected quality (40%) for zinc smelting or ISP. Na₂CO₃ solvent can be reused more than ten times without reducing the removal efficiency of chlorine.

View full abstract

An experimental study of causes of lead release from molten and water-granulated slag revealed that the lead content in waste affects the lead content in molten slag, its release from the molten slag, and lead concentration in the granulation water. The granulated slag itself and granulation water adhering to the slag are two conceivable causes of lead release. Experiments in a melting furnace in which granulation water contacts exhaust gas showed that lead in exhaust gas released into granulation water increases the lead concentration in the water. The following might improve the quality of granulated slag from melting furnaces of this type : (1) acceleration of lead volatilization ; (2) avoidance of contact between exhaust gas and granulation water ; (3) adjustment of granulation water pH to the neutral range ; (4) control of lead concentration in granulation water ; and (5) removal, through cleaning, of water adhering to the slag.

View full abstract

Physicochemical and biological parameters and the microbial community were investigated in cattle manure compost that was manufactured in a large-scale compost plant that uses a force-aerating and auto-blending fermentation system and a piling method. The microbial community was investigated by phospholipid fatty acid (PLFA) analysis. This compost plant produces good quality compost using two-step fermentation processes. The microbial biomass reached maximum value at day 5 from composting and then decreased gradually. The microbial diversity decreased up to day 10, then increased rapidly and reached a plateau after day 20 from composting. Relative changes in gram-positive bacteria and some bacteria related to anaerobic condition were remarkably large during the first fermentation with the force-aerating and auto-blending system and the second fermentation with the piling method, respectively. There was a highly positive correlation between the proportion of biomarker fatty acids for gram-positive bacteria and the value of the germination index, suggesting that PLFA analysis could be used as a tool for evaluating the maturity of the cattle manure compost that was produced in this large-scale compost plant with the force-aerating and auto-blending fermentation system.

View full abstract

A significant amount of livestock waste is generated in Miyazaki Prefecture and a large part of it is applied to agricultural land as manure. It has been reported that the surplus application of livestock waste contaminates groundwater with nitrogen and causes the accumulation of phosphate in soil, which could also lead to eutrophication. To preserve the quality of this water resource, effective measures should control the application of surplus nutrients. The purpose of this study is to estimate the nutrient (nitrogen and phosphate) balance, and provide fundamental data for designing an organic waste recycling system suitable to the conditions of Miyazaki. The estimated amounts of nitrogen and phosphate applied to agricultural land are approximately 2 and 3 times higher than those of standard applications. These results suggest that, to conserve water quality, livestock waste should be used not only for compost but also for other products such as alternatives to chemical fertilizers and industrial materials.

View full abstract

We have conducted a questionnaire survey in three areas of Hokkaido on the following two matters : 1) the present status of the compliance of cattle farmers with the livestock excreta control law, and 2) their awareness of automatic spiral agitation composting and biogasification facilities for livestock excreta, which are both effective facilities for achieving the purpose of the law. The survey results revealed problems and possible strategies in promoting the appropriate treatment of livestock excreta and its effective utilization.
The ratio of cattle farmers using law-abiding composting facilities (LACF) as mere storage facilities for livestock excreta was about 30-60%. On the other hand, about 30% of farmers leave livestock excreta in the open before they spread it on their farms. Thus, it is important to further promote effective use of LACF and appropriate management of excreta outside of LACF.
Most of the cattle farmers have no intention of constructing automatic turning type composting and biogasification facilities at this moment. Sufficient objective data about their merits, costs, and labor related to installation are important to promote their installation.

View full abstract

Hearing surveys were conducted in order to determine the reasons behind host-community opposition to the construction of solid waste management (SWM) facilities. The ten SWM facilities surveyed include incinerators, landfill, and shredding-separation facilities for municipal and industrial solid waste. Four to six residents living in proximity to the facility were selected at each location, and asked to talk freely about the facility and what they thought of it.
It was concluded that the reasons for opposition can be categorized into two groups : 1) physical and nonphysical impacts ; and 2) a lack of trust in the operators, planners, and overall decision-making process. The two categories were specific to all the facilities surveyed, regardless of the type of facility or the type of solid waste it handles. Acceptance by the locals suggested that at least one of the two should be positive. Nevertheless, in cases where construction of a facility was accepted, it was suggested that credibility and reliability of operators is far more critical in reducing opposition and building good relations with the surrounding residents.

View full abstract

Investigations and analysis were conducted to determine the amount of materials flowing into, circulating within, and flowing out of the eco-town in Kitakyushu in order to obtain information for a subsequent comprehensive evaluation of the eco-town project. The majority of materials going into the eco-town are being incorporated as resources to produce usable materials and energy, and the rest are treated and sent to companies outside the eco-town for further processing, recycling or final disposal. The ultimate material recycling rate is at 74% and the ultimate recycling rate, including thermal recycling, is as large as 94%. Within the eco-town, these rates are at 65% and 75%, respectively. The recycling rate is larger for metals, inorganic materials, plastics and biomass (increasing in this order). A portion of economically valuable materials is 24% of the total amount of material entering the eco-town, and increased up to 66% for materials leaving. There are many material-processing companies located intensively in the eco-town, but the cooperative activity among them is not sufficient and there is still room for improvement.

View full abstract

Due to the fact that few studies analyzing cost structure of municipal solid waste in Japan, we argue the cost structure using five years of MSW panel data. Estimation results showed that landfill costs could be reduced if treatment is set up for wider municipal areas rather than just one municipality at a time. It was also found that cost saving will occur if a separate collection for paper containers is established, rather than disposing of these as burnable waste, as is currently being done.

View full abstract

This research focused on photodegradation of Hexachlorobenzene (HCB) in hexane, isopropanol, and methanol. The photodegradation rates and degradation pathways were investigated and compared among these three solvents. Photodegradation of HCB preceeded reductive dechlorination processes and followed a first-order reaction kinetic. The degradation rate constants of HCB in the three solvents were 0.55 min^-1 in hexane, 0.48 min^-1 in isopropanol, and 0.37 min^-1 in methanol. Photodegradation rates of HCB and the dechlorinated products were affected by the solvent species. In all solvents, the major photodegradation pathways of HCB were as follows : HCB→P5CB→1245-T4CB · 1235-T4CB→124-T3CB · 135-T3CB→13-D2CB · 14-D2CB→MCB. The presented data showed that the solvent species affects the photodegradation rate of HCB, but not its dechlorination pathways.

View full abstract

The properties of illegally dumped waste and long-term transition of pollutants from that waste were investigated at an illegal dumping site. The investigation results are described as follows. First, the site was excavated during 2003-2004 to remove buried waste. Many waste drums were discovered, in which waste oils such as gasoline, kerosene, engine oil, and coal-tar products remained. These waste oils contained toluene, xylene, tetrachloroethylene (PCE), and trichloroethylene (TCE). These pollutants had also contaminated the excavated soil. Second, a groundwater investigation around the site, conducted during 1990-2004, revealed contamination by volatile organic compounds (VOCs) such as PCE and TCE. Most of the PCE and TCE had degraded to cis-1,2-dichloroethylene. The total molar concentration of the three VOCs in groundwater had decreased since 2000.

View full abstract

Sorted collection is essential for the promotion of municipal solid waste recycling. Consequently, energy cost and the resulting emissions associated with sorted collections need to be thoroughly estimated in order to determine the net reduction effect of recycling in terms of resource-saving and environmental load. In this study, a questionnaire survey was conducted to understand the travel distance of collection vehicles, using factors such as fuel consumption, collection timings, etc. as the primary data. With a focus on plastic packaging in particular, data was collected for each waste classification before and after sorted collection of plastic packaging was established. The travel distance for collecting a certain weight of each waste classification in each municipality was compared with the estimated distance shown on the Grid City Model. In one municipality, the total travel distance did not increase as a result of sorted collection for plastic packaging. The total frequency was constant before and after sorted collection started here.

View full abstract

Volatilization characteristics of heavy metal chlorides from molten fly ashes under reduced pressure were investigated using model and molten fly ashes.
As a result, the volatilization rates of ZnCl₂, PbCl₂, and CuCl were found to increase with a pressure reduction, when the metal chloride's reagents were used separately. However, in the case of ZnCl₂-PbCl₂-CuCl mixture, the overall volatilization rate of heavy metal chlorides was found to be lower than the respective volatilization rates of ZnCl₂, PbCl₂, and CuCl. Further, a decrease in the volatilization rate of heavy metal chlorides was observed with the progress of volatilization of heavy metal chlorides. Based on these results, the volatilization rate of heavy metal chlorides was described by first order reaction kinetics with respect to heavy metal chlorides concentration in an ash sample.
Subsequently, the effect of fly ash composition in terms of Al₂O₃, NaCl, KCl and CaCl₂ on metal volatilization was investigated. As a result, the amount of volatilized heavy metal chlorides was found to decrease with an increase in Al₂O₃. Furthermore, the amount of volatilized heavy metal chlorides from real molten fly ash was 0.27∼0.65 times lower than that of model fly ash without addition of NaCl, KCl and CaCl₂.

View full abstract

In this study, experiments on the destruction of Halon 1301 were conducted in an industrial waste incineration facility with a rotary kiln, which has a significant record of destroying chlorofluorocarbons. As a result, gaseous Halon 1301 could be discharged stably from a tank and injected into the rotary kiln by putting the tank upside down and sprinkling water on the tank. The destruction efficiency of Halon 1301 could be below the required value depending on the technique and position of Halon injection into the rotary kiln. Based on these results, we demonstrated that Halon 1301 can be destroyed with high efficiency and safety by thoroughly mixing Halon with air in a pre-chamber and bringing the Halon into contact with the flame.

View full abstract