CO₂ emissions from ironmaking processes should be reduced to avoid global warming. One promising solution is the effective utilization of organic waste materials in ironmaking processes. In this study, fundamental research on the application of organic waste materials, carbonized municipal waste (CMW) and carbonized woody biomass (CWB), as reducing agents was conducted experimentally to make metal iron from iron oxide. In the reduction experiments of the mixture of iron oxide (Fe₂O₃) with reducing agents (CMW, CWB, coal and graphite), metal iron was obtained with CMW and CWB. This is because the reactivity of fixed carbon in CMW and CWB is higher than that in coal and graphite. As a result, CMW and CWB are usable as reducing agents to make reduced iron.

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The insoluble treatment of radioactive cesium in municipal solid waste incineration (MSWI) fly ash by soil-mixed geopolymer solidification using Akadama soil, which contained abundant amounts of SiO₂ and Al₂O₃, as an activated filler was investigated. The elution rate of radioactive cesium from the geopolymer solidified substance mixed MSWI fly ash and Akadama soil was suppressed to 0.55%, compared to 69.6% for raw MSWI fly ash, using the Japanese No.13 leaching test. Almost all radioactive cesium in MSWI fly ash was insolubilized by mixing it with Akadama soil, which showed ability as an active filler and adsorption potential for radioactive cesium. A tank leaching test was applied to confirm the long-term stability of the geopolymer solidified substance. The geopolymer solidified substance showed stability in contact with pure water and on ultraviolet radiation. The geopolymer solidifying method using Akadama soil is effective as an insolubilization treatment of radioactive cesium in MSWI fly ash. This method could be applied to other waste materials.

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This study presents a mathematical model for predicting leachate concentrations from waste landfill layers and model validation results. The mathematical model is a well-known advection-dispersion equation with the results of serial batch leaching tests added as a source/sink term. One problem of this method is that the serial batch leaching tests evaluate at a liquid-solid ratio of 10, whereas the landfill layer targeted for prediction has a low liquid-solid ratio of about 0.5. This study focused on this liquid-solid ratio difference and improved accuracy of numerical simulation. Long-term batch leaching tests were conducted with different liquid-solid ratios from 0.5 to 100. Then, the leaching model was verified by comparing the measured values in this liquid-solid ratio batch leaching test with the predicted values obtained from numerical simulation using the results of the serial batch leaching tests. In order to practically calibrate the leaching model with low liquid-solid ratios, correction coefficients were defined by dividing the measured values into the predicted values. Finally, column leaching tests were conducted to check the effectiveness of the mathematical model using the correction coefficients. It was found that effluent concentrations of monovalent and divalent ions could be predicted with good accuracy.

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To reduce the governmental administrative burden of collecting waste and to make discharging recyclable wastes for residents more convenient, this research is a testimony to the efficiency of recyclable waste collection stations set in the Tohoku area. The paper discusses flexible application methods developed through the investigation of waste collection data. Moreover, the research surveys the application status of recyclable waste collection stations and analyses comparisons between behavior characteristics of users in a large city and a rural township.
　Our results found that most users of recyclable-waste collection stations is are in the 40 to 60 age range, while many older individuals are also using the collection stations. A station set in a city has an efficient resource collection rate in relation to a high car ownership ratio. Furthermore, compared to waste collection systems built by local governments, private recyclable-waste collection stations are able to collect more waste papers, metal products, computers, and cellphones, with a lower collection frequency. Also, users are motivated since they can get certain points by discarding recyclable waste items at these waste collection stations. Accordingly, the collection stations set by the recycling companies reduce the economic burden of local governments when it comes to collecting waste, as well as increasing convenience for separating and discharging recyclable waste and improving environmental consciousness among residents.

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The amount of landfill is expected to be reduced by improving the efficiency of waste treatment. Waste is classified into two types: general waste and industrial waste. The annual amount of industrial waste is about nine times that of general waste. About 80% of industrial waste is recycled, reduced, and finally treated at intermediate treatment facilities. This indicates that the efficiency of waste treatment in intermediate treatment facilities is the most important factor in improving entire waste treatment systems. Waste treatment planning in intermediate treatment facilities depends on the past experience and intuition of workers, which may not provide the best decisions. Moreover, waste may not arrive as planned. In this paper, we proposed a linear programming-based optimization method for waste treatment planning and employ an unexpected arrival variation-aware parameter (i.e., processing surplus ratio) to improve the efficiency of waste treatment in intermediate treatment facilities. We show that our proposed method can improve total cost when compared with actual data. We also show that, with an appropriate processing surplus ratio, it is effective even when the arrival volume of waste changes.

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In this study, the effects were evaluated of the fine aggregate volume ratio and particle size of waste bamboo charcoal on the compressive strength, moisture content, and electrical resistivity of hardened mortar that uses waste bamboo charcoal as a fine aggregate. As a result of comparing the general formula for the relationship between compressive strength and volume ratio with experimental values, it was found that the coefficient of determination R² of hardened mortar was as high as 0.980 by fitting with the Ramos-Shah formula. In addition, by comparing the general formula for the relationship between electrical resistivity and volume ratio with the experimental values, it was found that the electrical resistivity of the hardened mortar was close to the results obtained by fitting the Landauer equation and the experimental values, and the coefficient of determination R² was confirmed to be 0.981. Moreover, impedance analysis was performed on hardened mortar that used waste bamboo charcoal with a particle size of 1.2mm in an absolute dry condition. As a result, the equivalent circuit of the hardened mortar could be explained by conductive path, discontinuous conductive path, and insulation path and the values of various components could be calculated.

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Because fly ash is a specially controlled of municipal solid waste (MSW), it is treated with insolubilization, mainly chelation, to prevent leaching of Pb and other substances, before disposal in landfills. When chelated fly ash is landfilled, residual chelate and chelate-derived COD and nitrogen are eluted into the leachate. Residual chelate causes nitrification inhibition in the leachate treatment process, but chelate-derived COD and nitrogen are persistent. Moreover, they interfere with leachate treatment. Results of experimentation have confirmed that oxidation, such as using ozone, can decompose residual chelates, but decomposing chelate-derived COD and nitrogen is difficult. Given this background, after constructing an electrolysis apparatus using a piperazine chelating agent, we conducted experiments to decompose residual chelate, COD, and T-N.

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Various problems arise when it comes to taking out household garbage. For example, people are confused about garbage collection dates, they sometimes forget which day to take their garbage out, or they do not know the rules for putting out and sorting their garbage. In recent years, many local governments have introduced garbage separation apps in response to these problems. This research investigates the functions provided by the current garbage separation apps, and examines the intentions and effects of their introduction by local governments, while also surveying the functions that residents found to be most convenient and necessary. As a result, many local government garbage separation apps have been equipped with function such as ‘Calendar’, ‘Garbage Classification List’, ‘Garbage Separation Dictionary’, etc. These functions are being used frequently and residents have found them to be convenient. Results of the survey also revealed that the functions related to oversized garbage are in high demand and there have been many requests. After the introduction of the garbage separation apps, the operational effects in local governments include a reduction in telephone inquiries, easier conveyance of information to residents, a reduction in waste discharge mistakes, and an increase in awareness regarding the need to reduce garbage.

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Accumulation of propionic acid should be avoided for the stable operation of anaerobic digestion processes. This study focused on the effect of adding granular activated carbon (GAC) on Direct Interspecies Electron Transfer (DIET) to accelerate the decomposition of propionic acid and increase the amount of methane production. In addition, the effects of the GAC addition ratio and the addition of GAC with valuable microorganisms (bio-GAC) on the decomposition of propionic acid were investigated. This study added GAC in ratios of 0, 0.1, 0.5, 1, 2, and 5% in 40-day batch-type anaerobic digestion tests. The addition of GAC at 0.1, 0.5, 1, and 2% increased the amount of methane production more than two times compared to 0%. In contrast, the addition of 5% GAC did not increase the amount of methane production after the 12th day. This study indicated that the addition of GAC can accelerate the decomposition of propionic acid and the appropriate ratio of GAC should be used to obtain a positive effect in anaerobic digestion processes. Furthermore, bio-GAC accelerates the decomposition of propionic acid better than non-bio-GAC.

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This study examined emissions of unintentionally produced persistent organic pollutants (POPs) from fabric filters in aluminum alloy smelting plants. The results are expected to indicate means of reducing these emissions from sources, such as metal smelting furnaces, where emission control by existing exhaust gas treatments is insufficient. Measurement of dioxins and polychlorinated biphenyl (PCB) concentrations in fabric filters revealed their formation at around 100°C, at which temperatures these by-products were presumed to be formed only slightly. In laboratory experiments using fly ash collected from fabric filters, formation was confirmed below 100°C by long-term heating of more than 18 hr or preheating above the set temperature. This heating was regarded as necessary for reactivation of the catalysts in fly ash. Comparison of fly ash samples collected from three plants elucidated that water-soluble chlorides such as potassium chloride were the principal source of chlorine during formation at low temperatures. This comparison led to the inference that water spraying of flue gas is effective for reducing dioxins and PCB emissions from aluminum alloy smelting plants.

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We investigated the impact on greenhouse gas emissions (GGE) from nationwide introduction of a plant biomass mixed dehydration system at wastewater treatment plants (WWTP). The system is targeted at WWTPs that use belt press dehydrators, screw press dehydrators and centrifugal dehydrators.
　Results showed that installing a plant biomass mixed dehydration system at a WWTP can reduce GGE by 7.8%-12% through incineration at the WWTP. Furthermore, moving dehydrated cake away from WWTP and disposing of it can reduce GGE by 7.1%-7.7%. Moreover, by reducing coagulant amounts used for the system, we were able to reduce GGE by 5.8%-6.3% and 12%-22%, respectively.
　Results show that the introduction of a mixed dehydration system for plant biomass in WWTP can reduce GGE and can provide effective utilization of unused plant biomass and reduction of sludge disposal costs.

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In this study, we estimate greenhouse gas (GHG) emissions from municipal solid waste incinerators (MSWIs) in the city of Kyoto, Japan, for the year 2050. First, municipal solid waste (MSW) characteristics are analyzed and a calculation model for GHG emissions from MSWIs is established. We then estimate changes in the amount and quality of MSW in Kyoto based on past trends. Finally, five scenarios are evaluated: business as usual (S1); waste reduction (S2); S2 plus alternative use of bio-based plastics (S3); S3 plus enhancement of power generation efficiency (S4); and S4 plus installation of methane fermentation facilities (S5). In addition, scenarios with a decreased CO₂ emission factor for electric power due to the introduction of renewable energy (S1-6 to S5-6) are also evaluated here.
　All of the scenarios up to S4 could indeed reduce net GHG emissions to below zero by 2050. However, in the cases of S1-6 to S5-6, GHG emissions from electricity consumption and GHG reductions from electricity generation were almost eliminated. Moreover,even in S5-6, which had the lowest net GHG emissions, they were only 15.2% lower than in S1. S5-6 clearly shows that at least 20.3% of direct CO₂ emissions must be captured and sequestered to reduce net emissions below zero by the year 2050.

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Convection-diffusion simulation, which models physical and chemical behavior by numerical analysis, is effective for assessing the impact of naturally-derived shavings that contain heavy metals at disposal sites.If proper modeling is possible, it will be useful for optimizing excavation landfill site. The authors investigated the elution behavior of arsenic in the embankment at the Oshikado tunnel excavation site in Iwate Prefecture, where containment measures were taken with bentonite mixed soil. From the survey results, the hydraulic characteristics in the embankment and the elution characteristics of excavated material were considered. However, since sufficient elution characteristics cannot be verified based on the results of field survey alone, we further conducted column tests in saturated and unsaturated states using excavation slips at the same site, and we used the elution flow rate of the convection-diffusion equation for the reference elution flow rate, maximum elution amount, volumetric water content, and flow velocity. When the experimental results were simulated by numerical analysis, the elution amount could be reproduced with a certain degree of accuracy.

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This manuscript focuses on temperature as the standard parameter for landfill closure. In order to grasp the temperature characteristics of an inert waste landfill site, the temperature of the waste layers over a 16-year time period were summarized. The waste layer temperatures may rise to under 40 degrees Celsius immediately after dumping. The temperature gradually decreased at a relatively stable temperature gradient after landfill completion, and it tended to converge at around 25 degrees Celsius after two years. The temperature of the waste layer was influenced by the degradation of organic waste, the heat accumulation in the waste layer, and the heat transfer from outside temperatures and rainwater percolation. However, because the amount of organic matter in the inert waste landfill is small, any influences on temperature transfer to the waste layer tend to finish in a short amount of time. Therefore, it was observed that the temperature of the waste layer below a depth of 10m is influenced by many factors, but no influence was observed in the waster layer above a 30m depth. From these results, we can conclude that after a period of two years, inert waste landfill sites can generally meet the temperature (less than surrounding underground temperature plus 20 degrees Celsius) standard for landfill closure.

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To utilize the incineration ashes of biomass fuels effectively, the recovery of potassium and phosphorus contained in them was examined. Through sequential iterative extraction of potassium and phosphorus from mixed ash (bamboo chips, cow dung pellets, sewage sludge pellets), potassium was selectively extracted without loss of phosphorus by using 0.01mol･L⁻¹ HCl. In addition, by adding 70% H₂SO₄ to the phosphorus-containing extract that was used once for phosphorus extraction, the extract could be used again as an extractant. By repeating the phosphorus extraction three times, the phosphorus concentration in the extract was increased by as much as about 2.8 times. Therefore, it was possible to extract potassium and phosphorus continuously from the same mixed combustion ash. The water-soluble potassium content in the recovered potassium compound was 39.6%, and the content of citric-soluble phosphate in the recovered phosphorus compound was 15.7%. Both the recovered potassium compound and phosphorus compound can be used as raw materials for by-product fertilizers with high concentrations of fertilizer components.

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With the goals of reducing the amount of biodegradable plastic use and developing the utilization of Okara, which is a byproduct of tofu production, the mechanical properties and dimension stability with vapor and liquid water adsorption of polybutylene succinate sheet mixed with dry Okara at 20 and 30wt%(20wt%- and 30wt%-Okara/PBS sheet) were evaluated. Based on the thermal decomposition behavior of Okara, it was determined that the Okara and PBS should be kneaded in 185°C conditions. From the results of tensile tests, the Okara/PBS sheets showed high tensile stress and stiffness compared to the PBS sheet. This mechanical property change might be caused by the adhesion interaction between PBS and dry Okara. In addition, the moisture and water adsorption amounts of the Okara/PBS sheets were more than those of the PBS sheet. Furthermore, although the dimensional stability of the Okara/PBS sheets was lower than that of the PBS sheet, the dimension change of the 30wt%-Okara/PBS sheet was only 1.1% when immersed in liquid water. Finally, Okara/PBS sheet could be used as a packaging material.

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This study aims to investigate a new high-temperature compression molding method that uses dies for recycled polystyrene in flake form. When successfully developed, this proposed molding method is expected to contribute to reduced costing and CO₂ emissions. Since the colors of the material do not mix, this method enables designs that have not been possible with conventional methods. In this study, sheet products, which are the most basic shape achieved with the hot press, were formed using this method. The thickness of the products was measured and bending tests were performed to investigate the mechanical characteristics of the products that were formed. In the forming method usually used, voids are confirmed within the product. Therefore, in order to remove internal voids, an attempt was made to form the product using sequential molding and bottom heat molding. The results confirmed the plate material could be largely removed with bottom heat molding. Also, the bend-strength of the molded product using both sequential and bottom heat molding increased by 10% when compared to conventional molding methods.

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This study examines appropriate transportation distances for the proper disposal and recycling of industrial wastes. We conducted the analysis by combining the results of a questionnaire survey with information held by local governments. Specifically, we calculated the capacity of waste treatment facilities in Kitakyushu City and the percentages of wastes that could be changed based on the reasons for choosing the disposal sites. Then, we determined the amount of waste to be transported and treated outside of Kitakyushu City by optimization calculation. Furthermore, we quantitatively evaluated the results in terms of carbon dioxide emissions. The results showed that treatment facilities in the city have enough surplus capacity, except for the facility for ash. As for the possibility of changing destinations, some wastes, including oil, acid and alkali, are difficult to treat. On the other hand, the destinations of some wastes, including animal and vegetable residues, mineral waste and wood, could be easily changed. In addition, we solved the transportation problem to minimize the transportation ton-km and obtained a maximum effect of reducing carbon dioxide emissions by 51% from the current level, quantitatively showing the effect of measures to shorten transportation distances.

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In this study, we interviewed 12 Japanese stakeholders and summarized the characteristics of each of the advocator’s perceptions on Extended Producer Responsibility (EPR), focusing on the type, aim, application, rationale, and scope of “producers” of EPR. The stakeholders pointed out that not only is financial responsibility important but also physical and informational responsibilities. They also placed the rationale of capability as the main and causality as the sub to justify EPR. The authors then argued the different approaches for introducing and developing EPR policy, such as a physical responsibility-oriented approach and a policy-mix approach; noting that these depend on the ambition of advocator with regard to the ultimate goal and preferences for the different modes of government intervention. Furthermore, the authors explained, based on their discussion about differences in the stringency of responsibility/liability imposed on producers, how there is a tendency for confusion between the responsibility theory for mandatory EPR and the liability theory for producer obligations. Lastly, we also point out an issue that EPR theory, from the perspective of innovation, has not been developed in Japan.

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The gas fluxes from two pieces of gas ventilation equipment and a monitoring well in a controlled landfill site for industrial waste with about 45 meter depth were investigated using hot-wire anemometers for 18 years.
　In the composition of the landfill gas, the methane to carbon dioxide ratio was high. The maximum concentrations of methane and carbon dioxide were 81.6% and 12.3%, respectively. The concentration of landfill gas decreased year by year.
　The average gas flux on measurement days was 203 L/min at maximum and tended to decrease year by year. From factor analysis using 10-minute intervals, the gas flux decreased when atmospheric pressure rose for the most recent interval. In contrast, the gas flux tended to increase during decreases in atmospheric pressure. The rate of increase of the gas flux decreased after much gas emission.
　From factor analysis at 1-minute intervals, it was inferred that atmospheric pressure changes in several tens of minutes influenced the gas flux of the whole landfill site, and the atmospheric pressure change in several minutes influenced the fluctuation of the gas flow near the gas ventilation equipment.

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In this study, to promote the use of cullet in construction and improve the quality and stability of foamed cement banking (FCB), we proposed using green waste glass cullet (green GC) in GC-FCB, tested its formulation, observed the internal structures of FCB samples using microfocus X-ray computed tomography, and conducted an alkali-silica reactivity (ASR) test. (In this study, the test measured changes in the length of air mortar bar for each material age.) The results confirmed the following. 1) Green GC with a fineness modulus of 1.7-2.6 is most suitable for FCB, and FCB that uses green GC is anticipated to be stronger than FCB that uses natural sand. 2) The internal part of the proposed GC-FCB specimen has a relatively uniform distribution of green GC with consistent diameter. 3) Even if green GC with high silica content is used for FCB, the risk of ASR degradation is low.

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Information about waste properties (heating value, water content, etc.) is important in waste incinerating operations. However, investigating the properties of infectious waste discharged from medical institutions is difficult to due to its infectiousness. In this study, the properties of infectious waste were investigated by considering the heat balance and material balance in a waste incineration plant that co-burns infectious waste and industrial waste. The total amount of heat generated in the incinerator was estimated by considering the amount of heat in the combustion gas. Then, the lower heating value of the infectious waste (28.3MJ kg⁻¹-wet) was estimated by subtracting the amount of heat derived from the industrial waste from the total amount of heat. The proportions of chlorine (3.23wt%-wet) and ash (4.93wt%-wet) in the infectious waste were estimated by the same method. The chlorine and ash derived from the industrial waste were subtracted from the total amounts output from the incinerator. To obtain the properties of the infectious waste itself (not including containers), the contribution of sealed containers (plastic containers and cardboard boxes, total 14.7wt%-wet) were estimated. The biobased content of the infectious waste itself (14.2%C) was estimated by analyzing ¹⁴C content in a sterilized sample.

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Case studies of energy recovery and CO₂ reduction were conducted for processes used for converting sludge to energy (digestion, carbonization, drying, and composting drying) and for combined processes of digestion and drying. Effects of drying efficiency on energy recovery and CO₂ reduction during sludge drying were also examined. Results show that recycling by digestion was best in terms of energy recovery and CO₂ reduction. However, if the drying process improves drying efficiency to greater than 80%, then energy recovery is expected to be equivalent to that achieved using the digestion process. Moreover, CO₂ reduction is much greater than that achieved by digestion. The composting recycling process is superior in terms of energy recovery and CO₂ reduction, but important difficulties hinder the use of compost as a fuel under present conditions.

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Controlling the elution of heavy metals from municipal solid waste incineration (MSWI) fly ash using water repellent treatments was studied. Water repellent durability and adaptability to the environment in the final disposal site are required for landfilling water repellent MSWI fly ash. Three types of elution tests, including Ministry of the Environment Notification Test No.13, were carried out to evaluate the elution suppression effect of water repellent treatments with six fatty acids (oleic acid, linoleic acid, α-linolenic acid, isostearic acid, ricinoleic acid, and erucic acid). All six water repellents could suppress the elution of heavy metals from MSWI fly ash. The elution suppression effects on heavy metals differed depending on the physical and chemical properties of the fatty acids. Water repellent treatments with fatty acids demonstrated effectiveness in the suppression of heavy metal elution in two types of fly ash with different incineration methods and indicated adaptability to the environments of final disposal sites. Based on the results of three types of elution tests, water repellent treatments with fatty acids have the potential to replace conventional methods as new treatments for suppressing the elution of heavy metals from MSWI fly ash.

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Effective utilization of the nutrients contained in anaerobic digestion effluent (ADE) for microalgal cultivation requires removal of pollutants without reducing the nutrient contents. This study was conducted to develop an ADE treatment with appropriate technologies in developing countries. Slow sand filtration (SSF) is a simple, low-cost technique. Activated sludge (AS) process can enlarge particles in ADE with floc formation. Activated carbon filtration is effective for color removal. Therefore, a combination of AS process, SSF, and activated carbon filtration was attempted. The combined process removed 91% of suspended solids. Subsequently, SSF removed 69% of the suspended solids remaining after AS process. Probably, SSF in the combined process maintained a higher removal efficiency because AS promoted flocculation of small particles in ADE, thereby enabling easier trapping of particles on the sand. The average removal efficiency of dissolved organic carbon by activated carbon filtration was 47%. Also, the absorbance of photosynthetically active radiation was lower by 70%. However, inorganic nitrogen and phosphorus concentrations remained after treatment. Taken together, the results indicate that the combination of the three treatments can selectively purify ADE while retaining nutrients for microalgal cultivation.

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Hydrothermal synthesis of hydroxyapatite (HAp) using calcium acetate prepared by dissolving scallop shells in acetic acid led to a high adsorption rate of 97% for acidic protein and a low rate of 24% for basic protein. These are advantageous properties for adsorbents used for acid-base separation. The adsorption property was attributed to the needle-like crystalline shape of HAp. The strontium ions and organic compounds present in scallop shells were assumed to be responsible for the needle-like shape of HAp. These components are not present in limestone. Therefore, synthesis of needle-shaped crystals of HAp was not possible under the same hydrothermal synthesis conditions. Results confirmed scallop shells to be beneficial as a raw material for HAp synthesis by hydrothermal reaction.

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