Construction sludge is often modified in the process of generation or intermediate treatment, and the modified sludge often shows high alkalinity. Recently, as one of the methods to reduce the pH of such alkali construction sludge, the modified construction sludge is placed in a pool and aerated with CO₂ gas from the bottom to the top. However, it is difficult to monitor the progress of neutralization of the modified sludge and to predict the completion time.

In this study, we conducted a column-type neutralization test in which CO₂ gas was aired into a cylindrical specimen and simulated the test results to investigate efficient neutralization conditions by predicting the progress of neutralization and completion time. The results showed that the amount of CO₂ input that does not contribute to neutralization could be suppressed by changing the flow rate in the middle of the flow rate for a constant flow rate condition, while keeping the completion time of neutralization the same.

Coal bottom ash (CA) generated from the bottom of coal boilers contains soluble boron and the level of the concentration often exceeds the Soil Environmental Standard value for Boron. The relationship between boiler combustion conditions and soluble ions in CA were investigated to estimate the factors that cause fluctuations of boron contained in CA. The results showed that there was no significant relationship between the soluble boron and the combustion conditions of the boiler. It was found that the soluble boron in CA has a relationship with concentrations of calcium and sulfate measured by the leaching test. It was found that the saturation index values of gypsum in CA obtained by PHREEQC software with higher soluble boron was larger than that with lower soluble boron. This result indicates that the soluble boron in CA was embedded or adsorbed in gypsum and the variation of soluble boron would be influenced by the amount of gypsum in CA.

While international trade in used vehicles prolongs their use and contributes to the effective use of resources, there are concerns about improper disposal of end-of-life vehicles and inefficient resource recovery, as well as air pollution in developing countries. With the globalization of the economy, including new vehicles, generating benefits around the world, it is necessary to discuss how to realize efficient resource recycling as a whole. In this context, it can be assumed that Japan exports to developing countries, but it is not certain what proportion of these exports are made by Japan. In addition, the structure of used vehicle exports from the United States and the European Union (EU) may not be similar to that of Japan. As a result of this study, it cannot be said that used vehicle exports have a route structure from developed countries to developing countries based on the DAC list alone, but by including transit points or using the IMF list, it can be said that the majority of used vehicle exports from developed countries are to emerging and developing countries.

Reused photovoltaic modules are required to demonstrate their quality and performance as products by evaluation IV performance, EL performance, visual inspection, and insulation performance. However, it is necessary to use dedicated measuring instruments for each quality assessment witch this tends to increase installation costs and maintenance costs. It increased cost of the quality evaluation process is contrary to the advantage of reused products, which is that they can be introduced at a low cost. Therefore, there are concerns about price of reused photovoltaic modules will increase and uncontrolled quality products are exported out of the country.

We have studied a method that makes it possible to estimate peak power by analyzing EL images. This will establish a method that does not require "IV measurement equipment," which is the most expensive equipment to install and operate.

Lithium-ion batteries (LIBs) have superior characteristics compared to other rechargeable batteries, such as high energy, high capacity, and high voltage. Polyvinylidene fluoride (PVDF) is used as a binder resin for the cathode of LIBs. The aim of this study was to achieve halogen recycling, so we focused on WEEE-derived LIBs and conducted experiment for fluorine recovery from spent LIBs. Furthermore, the recovered CaF₂ was evaluated in comparison with fluorspar as the primary raw material.

In recent years, smoke and fire accidents have occurred frequently due to crushing of lithium-ion batteries (hereinafter referred to as "LIB") mixed with other waste at the time of waste collection and treatment. In this study, with the aim of constructing an LIB detection system using RFID tags, an automatic recognition technology, we conducted experiments to confirm the basic performance of the tags and to read the tags at multiple measurement sites, using RFID tags currently under development. The results showed that the tags could be detected even when attached to products containing metal objects that weaken radio waves due to their unidirectional directivity. Even in the daily life environment where other radio waves such as Wi-Fi are also flying, the reception performance was confirmed to be equivalent to that of an anechoic chamber if the reception distance is 1 m or less in the laboratory and 2.5 m or less outdoors. Further experiments and studies of detection methods will be conducted for practical use.

Electric vehicles are becoming more popular toward carbon neutrality, and recycling of rare metals (Li, Ni, Co, Mn) from used LIB is essential for the stable supply of LIB. The treatment conditions of the recycled LIB vary, and the particle size and components of the obtained black mass powder sample are inhomogeneous. It is also known that the Al component used in the battery exterior and the current collector undergoes an alloying reaction with Ni and Co in the process of heat treatment and exists in an inhomogeneous state.

In this study, we examined a sample preparation method for the purpose of accurately analyzing the composition of rare metals and impurity components in black mass samples by X-ray fluorescence analysis. Rare metals and impurity components were analyzed by using standardless FP method for black mass samples obtained by different sample preparation methods, and differences with ICP emission analysis values were compared.

An enormous amount of photovoltaic panels (PV panels), which have been introduced rapidly since the beginning of 2010s, will become End-of-Life (EoL) in 2030s and considered to cause large damage on the waste management system in Japan. We conducted surveys to understand the obstacles to the environmentally-sound management of EoL PV panels, especially their reuse and recycling, and the potential solutions. Material separation companies have pointed out that the efficient collection and transportation of EoL PV panels is crucial for encouraging both reuse and recycling. The efficient collection and transportation may be enabled by accumulating data regarding disposers of EoL PV panels through digital services. In order to propagate such digital services, according to our questionnaire survey to households that installed PV panels at home, the cost for collection and management of the EoL PV panels as well as trust to the service providers were found to be the key factors.

Waste Printed Circuit Boards (WPCB) contain gold, silver, and rare metals, and their recycling has great economic value. On the other hand, brominated flame retardants (BFRs) are sometimes added to the resin portion to provide flame retardancy. One of the BFRs, polybrominated diphenyl ethers (PBDEs) are under international regulation by the POPs Convention and RoHS Directive from the viewpoint of their adverse effects on human health and environmental persistence. Therefore, debromination of WPCB have great significance. In this study, it was examined the validity of the wet ball mill method with the addition of iron for efficient debromination of WPCB containing BFRs.

Electrostatic separation, which is a step used in sorting, is a sorting method that utilizes the difference in charge polarity as generated when different types of plastic are rub together or touch each other. In electrostatic separation, there is a problem that the recovery rate of plastic is not stable due to the seasonal fluctuation in the input material composition ratio. In this investigation, we modeled the seasonal fluctuation of the input material composition ratio and examined a method of determining the separation condition from the composition ratio estimated by the model to raise recovery rate in the second electrostatic separation process for sorting PS. We applied to a state-space model, which is one of the time-series analysis models, to the composition ratio data including sampling errors to estimate the true value, and devised a method to determine the sorting condition for electrostatic separation by inputting the estimated composition ratio into the drop distribution model. As a result of the recovery rate simulation, it was found that recovery rate was improved by about 3% compared to the case where the sorting condition was not adjusted.

The purpose of this study is to understand the events that cause LIB-induced ignition and fire incidents at municipal treatment facilities for noncombustible waste, etc., and to obtain knowledge that will contribute to countermeasures, including early detection and monitoring to prevent the spread of such incidents. For this purpose, real-time monitoring with measurements of surface temperature and various gas concentrations during the crushing and conveying processes at an actual facility was conducted to understand the ignition and other events at the treatment facility.

In recent years, the EU has been actively engaged in efforts and research on PfR (preparing for reuse), which involves sorting, cleaning, repairing, and reassembling usable items from used appliances. However, Japan has not made significant progress in this area. In this context, Yamada Holdings stands out as a company that collects and sorts used appliances in its stores, transporting them to reutilization facilities for PfR. They have successfully established an efficient and technologically reliable system, enabling the provision of affordable reused products and creating a positive cycle for the environment and the economy. If other retailers can collaborate in building a shared system, PfR could make significant advancements.In addition to collaborative efforts among retailers, the progress of PfR requires the cooperation of manufacturers in ensuring a stable supply of parts. Furthermore, it is believed that a legal revision allowing retailers to participate in appliance recycling under the Home Appliance Recycling Act is necessary to redirect unsuitable items for reuse towards recycling. It may also be necessary to establish targets and obligations for retailers regarding the collection of reused items.

With the advancement of IoT technology, it is expected that sensors and devices containing large amounts of circuits and batteries will be dispersed into the environment, some of which will be left behind without being collected. However, the environmental impact of hazardous substances contained in these devices has not been adequately discussed. Therefore, we designed and evaluated low environmental impact batteries based on the material selection guidelines presented in the next section. We also conducted plant damage tests to evaluate the effects on plants when batteries containing high levels of chemical substances are disposed of in the environment. Furthermore, we evaluated the environmental impact of our low-environmental-impact batteries by analyzing the components contained in the batteries and commercial batteries, as well as by conducting the same evaluation for simulated waste that is assumed to be general waste.

We are promoting technological development of “highly functional” recycled material as an initiative to increase usage of recycled materials using plastic parts collected from waste home appliencies.

Among them, we developed a new durability evaluation method of frame retardant polypropylene recycled materials because the conventional method of measuring Oxidation Induction Time could not be applied.

This study is concerned with recycled polypropylene materials using collected parts from waste home appliencies that satisfy both the performance required for home appliencies and flame retardancy.

Among the developed technologies, an overview is reported especially on the durability evaluation method that takes into account the amount of additives that accelerate oxidative degradation of polypropylene and variations of waste materials.

Sri Lanka's western province faces several challenges related to solid waste management due to population growth, economic development, and changing consumer habits. Composting is a popular treatment method for organic waste in the country, but issues like offensive odors and technical difficulties hinder its efficient operation. To address these problems, an aeration system was implemented as a pilot project in the Kaluthara composting plant. The goal was to enhance composting facility efficiency, reduce offensive odors, and improve waste management practices, while also setting an example for future implementation in other Sri Lankan composting plants. Various parameters such as flow volumes, air pressure, temperature, moisture content, volatile solids, and air composition were regularly monitored during a trial phase. The results showed that the aerated compost piles consistently maintained optimal oxygen levels, and the installation of the aeration system led to a significant reduction in offensive odors which contributed to improving waste management practices in the Kaluthara composting plant, demonstrating the potential for future implementation of aerated composting systems in other composting facilities in Sri Lanka.

This study focused on developing a stable compost production strategy for agricultural by-products. The research aimed to optimize microbial activity during composting through three areas of investigation: understanding the characteristics of organic waste resources, developing pretreatment methods to enhance biodegradation, and exploring the use of microbial agents and biochar to reduce odors. The analysis revealed that agricultural by-products have high organic matter content and are suitable for composting, particularly when mixed with a ratio of 60% or more of livestock meal. Chemical pretreatment, targeting the combination of hemicellulose and lignin, was found to promote organic matter decomposition by microorganisms. Furthermore, the study demonstrated the effectiveness of soil and biochar as additives in reducing NH₃ emissions during composting. The addition of Bacillus sp. React3 (OL440405) also contributed to NH₃ reduction. However, when biochar and microorganisms were combined, there was a slight increase in ammonia concentration compared to the treatment with only microorganisms. The findings of this study hold promise for the development of compost production technology, aiming to promote the recycling of organic waste such as food waste, and stimulate the rural economy. By implementing efficient composting processes tailored to the characteristics of agricultural organic waste, the study seeks to contribute to a sustainable resource recycling system that addresses waste management challenges and environmental concerns

Mexico City generates about 12,500 ton/day of municipal solid waste, 44% are food scraps and yard trimmings. Since 2012 the Bordo Poniente Composting Plant (PCBP) processes 2,500 ton/day of the organic fraction of municipal solid waste (OFMSW) in 37 ha yielding 500 ton/day of compost. The purpose was to evaluate three treatments to reduce the composting time so more OFMSW could be digested. We built three piles with OFMSW in a relationship 70:30%v/v, the weight of each one was 150 kg. The treatments were: A (30 l of leachates with a count of 10⁶ CFUg⁻¹ and ground feedstock), B (ground feedstock) and C (30 l of leachates and raw feedstock). Moisture content of the feedstock was 75%. Piles were turned twice a week. Physical, chemical and biological parameters were determined. Solvita® Compost Maturity Test was used to measure stability and maturity. Treatment A showed a significant reduction in time (p<0.05) i.e., it took less to reach the thermophilic phase and maturity of the compost was achieved at 35 days whereas treatments B and C took 75 and 55 days, respectively. Grinding of the feedstock and inoculum addition reduces the composting time 61% to the time it takes at the PCBP.

In this study, an electrokinetic method using a 6 V solar cell was applied to saturated black soil mixed with cow manure compost (compost-mixing ratio was 47%), and a cultivation test of Japanese mustard spinach was conducted to confirm changes in productivity due to the application. As a result, the effect of oxidation reaction at the anode on the plant growth was extremely low. On the other hand, it was found out that the reduction reaction at the cathode significantly affected the plant growth. Specifically, the productivity in the soil within 40 cm from the anode was increased. In addition, the productivity in the soil around 20 cm from the cathode was affected by the reduction reaction. In the future, it is necessary to verify the effect of this technology under field conditions (drainage irrigation).

The objective of this study is to establish the model of deodorization mechanism using GLASS FOAMING MATERIAL. Ammonia gas was targeted as to remove component of odorants in this study. Ammonia gas is one of the main component of odor from composting facilities. We assumed that the deodorization mechanism consists of the dissolution into water which is holding in glass foaming material and the decomposition of ammonia by microorganisms. The modeling of deodorization mechanism was attempted by using theoretical equations such as the doble boundary membrane theory, Fick's law, and Monod's equation. The model were established using COMSOL Multiphysics, a physical simulator. The validity of the model was verified by performing calculations up to 30 hours after the start of the experiment under the same conditions as in the microbiological degradation experiment. The results of the calculations showed that the model represented well the experimental values of the concentration of each substance in the holding water. In addition, calculations were performed for up to 7 days with input of the operating conditions of the deodorization equipment used in the actual composting facility to confirm the reproducibility of the model.

Currently, compost derived from waste biomass is attracting attention due to the price of chemical fertilizers and other factors. However, some farmers are concerned about the quality of compost because there are no regulations on the frequency of component analysis of compost, and fertilizer components are not stable. Therefore, this study clarifies the stability of the quality of compost produced from food waste methane fermentation facilities. We also aimed to clarify the material balance of nitrogen and phosphorus, and to examine the possibility of further utilization of the compost. The analysis was conducted at a facility that produces compost by methane fermentation of food waste, and compost and its process were sampled and analyzed over an 8-week period from November 2022 to January 2023. The results of the analysis of compost components showed that fertilizer components (nitrogen, phosphorus, and potassium) were stable, and there were no significant changes in pH, EC, moisture content, or ash content. The analysis of the samples taken at the facility showed that phosphorus was recovered as a resource as compost. But half of the nitrogen was treated at water treatment facility, suggesting the possibility of using it as a liquid fertilizer.

In this study, biochemical methane potential (BMP) and digestion inhibition phenomena were evaluated for nine samples (supplements, furikake, cookies, soft candy, BBQ sauce, processed cheese, mascarpone, palm oil, and margarine) by a 30-day mesophilic digestion batch tests. In addition, semi-continuous reactor tests (mesophilic conditions) with a residence time of 40 days and parameter fitting of ADM1 based on the results of the tests were conducted to evaluate the maximum input amounts of processed cheese and palm oil. The batch test results showed that wastes with higher lipid content tended to cause digestion inhibition and had high BMP. On the other hand, margarine with high fat content showed relatively low digestion inhibition despite its high BMP. The semi-continuous reactor tests showed no digestion inhibition when the process cheese and palm oil were mixed with 3.3% of the Plant K waste input. The methane gas production rate in the palm oil was simulated by ADM1.

Since the “Global Methane Pledge” advocated at COP26 in 2021, methane emissions control has attracted attention as an effective means of reducing greenhouse gases (GHG). The steel industry, which is responsible for the coke blast furnace method, is also thinking about responding to and contributing to this movement. Specifically, by avoiding the landfill disposal of "organic waste" generated by households, which is common in many countries overseas, we will prevent the generation of methane derived from organic matter, and carbonize and import this to Japan. , used in the steel industry as a substitute for some coal. We show that this concept has several times the GHG suppression effect of coal replacement with simple woody biomass.

In the mackerel mirin-boshi production process, a large amount of liquid waste from pre-pickled seasonings consisting of sugar, soy sauce, miso, salt, and umami seasonings is discharged, it also has a high chemical oxygen demand (COD) requiring dilution. In poultry farms, soft eggs with soft shells produced by young hens account for about 15%, and these eggs are currently discarded. In this study, food waste such as mackerel mirin-boshi waste liquid or commercial hen eggs as soft egg model were applied as the protein source for ethanol fermentation. Moreover, COD reduction of waste liquid was investigated by conversion from liquid protein source to solid protein aggregation produced in yeast proliferation. The mackerel mirin-boshi waste liquid was a suitable protein source, because ethanol fermentation was promoted by its addition. However, COD reduction was not achieved to dischargeable levels into the environment river. In case of egg, it was also suitable as protein source for yeast growth. Moreover, inhibition of lysozyme in egg white during the fermentation was reduced by heat treatment or addition of ephedra herb as fermentation promotor.

ESG evaluation has become crucial in addressing global warming caused by increasing emissions of greenhouse gases. Biogas plants have gained popularity as they capture methane from organic waste and utilize it as energy. However, a significant amount of biogas remains unused, contributing to greenhouse gas emissions. To tackle this issue, a study was conducted on generating synthesis gas from biogas and utilizing the dry reforming of methane (DRM) reaction. Ni-based catalysts, commonly used for CO₂ methanation, were found to have limitations in low-temperature activity and sinterability. The study examined the catalytic efficiency with different methane-to-carbon dioxide ratios found in biogas facilities. Fe-Ni-CeO₂-Al₂O₃ catalyst exhibited stable operation over 50 hours, although its conversion rate was slightly lower compared to Ni-CeO₂-Al₂O₃. However, higher methane-to-carbon dioxide ratios led to decreased H₂ yield due to reduced carbon deposition resistance, as observed in SEM-EDS analysis. To prevent this, additional CO₂ injection should be implemented when CH₄ inflow increases. Therefore, the optimal conditions for implementing DRM in biogas facilities involve using Fe-Ni-CeO₂-Al₂O₃ catalyst and injecting methane and carbon dioxide at a maximum ratio of 1.2 to avoid carbon deposition and sintering.

This study investigates the co-cultivation of a genetically overexpressed strain of Clostridium acetobutylicum with sludge to enhance hydrogen production. Thiamphenicol, an antibiotic, is used to assess its impact on hydrogen production. The batch tests involve inoculating the modified strain and sludge in different thiamphenicol concentrations and monitoring hydrogen production rates and yields over 24 hours. Results reveal that the highest hydrogen production occurs at 25 mg/L thiamphenicol. However, hydrogen is also produced without thiamphenicol, thanks to the presence of other hydrogen-producing microorganisms like Clostridium butyricum and Clostridium perfringens. These findings demonstrate the successful co-cultivation of the modified strain with sludge, highlighting its potential for enhanced hydrogen production. The study concludes that while thiamphenicol influences hydrogen production, sustained hydrogen production can still be achieved without its use. This suggests the possibility of improving stability and performance in biological hydrogen production systems through alternative approaches.

The bio-methanation technology is a carbon-neutral technique that utilizes hydrogen gas derived from renewable energy and recovered carbon dioxide to be supplied to anaerobic reactors, where it is converted into methane by microorganisms. The bio-methanation reaction is controlled by the gas-liquid mass transfer of hydrogen. This study focused on enhancing the gas-liquid contact area and ensuring gas residence time, particularly for high-load continuous operation, by employing a foam-type reactor to improve the efficiency of bio-methanation. The foam system was capable of stable operation at a maximum hydrogen load of 8 LH2/LV/d and maintained a methane concentration of around 94%. The hydrogen consumption rate also reached approximately 99%. By utilizing the foam state, the gas residence time in this experiment was increased by about 18 times, and the gas-liquid contact area was increased by approximately 140 times compared to the gas-stirred reactor. As a result, it is believed that hydrogen was efficiently supplied.

Waste reduction and biogas production through anaerobic digestion are recognized as effective methods for converting organic waste into renewable energy. However, maintaining stable operation and efficiency in anaerobic digestion processes can be challenging. This study aimed to investigate the effects of physiochemical indicators and microbial communities on the operation of anaerobic digesters. A 10 L digester, equivalent to the size of six laboratories, was operated under various organic load conditions (1.0-6.0 kg VS/m³). Biogas yield and digestion efficiency were monitored in relation to changes in physiochemical properties.It was found that operating the digester under high organic load conditions (3.5-6.0 kg VS/m³) resulted in unstable biogas production. The duration of operation decreased as the organic load increased, with biogas yield approaching zero. Several indicators known to inhibit digestion, such as total ammonia nitrogen (TAN) concentration, volatile fatty acid (VFA) accumulation, VFA/alkalinity ratio, and pH, were monitored. TAN concentrations under the organic load conditions ranged from 1.9 to 2.3 g/L, which aligns with levels reported to inhibit digestion. VFA concentrations increased with organic load, reaching 5.86-9.06 g/L at the end of the operation. As VFA accumulated, pH decreased to 5.37-5.83. The VFA/alkalinity ratio, an indicator of digester performance, increased with the organic load, indicating acidification. Ultimately, the digester operation was discontinued due to acidification caused by VFA accumulation and decreased pH.

Toward the realization of carbon neutrality in 2050, methanation using waste-derived biogas and CO₂ and hydrogen derived from renewable energy is being studied. In this study, the potential of biomethane and synthetic methane obtained from waste incineration plants and their environmental performance were evaluated. In the evaluation, based on a general waste incineration plant (with power generation), there are 9 cases where a biogasification plant is attached, methanation is implemented (hydrogen is produced by surplus electricity or procured externally), and CO₂ recovered from incineration exhaust gas is used. We evaluated each one. As a result, when using CO₂ in the exhaust gas, the model that produces hydrogen with surplus electricity reduces the amount of CO₂ reduction, while the model that procures hydrogen externally increases the amount of CO₂ reduction. In addition, when using CO₂ in biogas, the amount of CO₂ reduction decreases in models that produce hydrogen using surplus electricity, while the model that procures hydrogen externally increases the amount of CO₂ reduction.

A continuous operation test of an AnMBR using liquid dairy biomass, mainly dairy manure, as feedstock was conducted to investigate the effect of HRT on anaerobic digestion. The biogas yield was 0.43 m3/kg-VS for 20 days HRT and 0.40 m3/kg-VS for 10 days HRT. Biogas yield decreased when HRT was further shortened to 8 and 5 days. The increase in the percentage of suspended solids in the total solids in the digester could be attributed to the fact that the hydrolysis stage was affected by the shortened HRT. On the other hand, at HRT days 8 and 5, the methane concentration in the biogas was above 70% and COD removal was above 90%, maintaining values similar to those at HRT day 20. These results indicate that AnMBR can be used to accelerate anaerobic digestion from liquid dairy biomass.

Anaerobic digestion is an energy production system in which organic wastes such as livestock manure and food waste are decomposed by anaerobic microbial metabolism and converted to methane. One of the challenges of anaerobic digestion is ammonia inhibition. Ammonia inhibition is a phenomenon in which the accumulation of ammonia generated during fermentation inhibits the bacteria, resulting in reduced fermentation performance. Co-digestion, ammonia stripping, and acclimation of microorganisms to ammonia have been considered as methods to deal with ammonia inhibition, but their low operability is a disadvantage. Therefore, we examined the use of additives as a simpler solution. It has been reported that the use of electron-transferring substances as additives can alleviate ammonia inhibition by promoting metabolic reactions in microorganisms. In this study, biochar was added in a continuous mesophilic anaerobic digestion test under high ammonia concentration conditions, and the effect of biochar on fermentation performance, including methane yield and volatile fatty acid concentration, was evaluated.

Addition of iron-based conductive materials such as zero-valent iron (ZVI), magnetite (Fe₃O₄) and iron(III) oxide (Fe₂O₃), and carbon-based conductive materials such as granular activated carbon (GAC) has been widely studied as a method to enhance methanogenesis in methane fermentation. However, there are few examples of studies comparing the effect of methane fermentation enhancement under the same conditions. In this study, batch-type methane fermentation tests were conducted using sewage sludge as a substrate under the same conditions, and the results showed that the average methane concentration increased about 1.1 to 1.2 times and the cumulative methane production increased about 1.2 to 1.3 times under the condition with the addition of ZVI compared to the condition without conductive materials. The results showed that the methane fermentation enhancement effect was higher than that of Fe₂O₃ and GAC.

Furthermore, the results of a batch-type hydrogen generation test conducted by adding ZVI to CO₂-saturated water confirmed hydrogen generation from ZVI, suggesting that hydrogen generated by the reaction of ZVI with H₂O and bicarbonate ion (HCO₃⁻) is involved in methane fermentation enhancement.

The purpose of this study is to clarify the effect of pre-pulverization on the energy crop Miscanthus Giganteus to increase the biogas production in the biogas plant. Some pulverizers were selected to earn five different pulverization particle sizes of M x g sample. In order to clarify the relationship between each particle size of M x g and methane production potential as a pre-pulverization effect, a batch-type methane fermentation experiment was carried out in the laboratory using 200 mL vials. As a result of the experiment, it was found that the methane production potential for 30 days was increased by pulverizing to 50 µm or less. the methane production potential of over 50µm size was 200 m3-CH4/kg-VS approximately. On the other hand, the methane production potential of M x g of 50µm size and less than 10nm size was 372 m3-CH4/kg-VS and 463 m3-CH4/kg-VS, respectively. Improvement effect of the methan production potential by pre-pulverization for M x g was demonstrated in this study.

Biochar produced from biomass has recently been promoted as a soil amendment and concrete admixture with carbon sequestration effects that contribute to the reduction of CO2 emissions. The characteristics of biochar that correlate with increased methane yield have also been investigated. In this study, a method for producing biochar with high specific surface area and high ash content was found by pyrolyzing biomass in a CO2 atmosphere using biomass fly ash as a catalyst. The effects of specific surface area and ash content on the yield, rate, and delay time of biochar produced by this method were investigated. The results confirmed that in the anaerobic digestion of fats and oils in the presence of biochar, biochar with high specific surface area reduced the methane potential while shortening the time to reach sufficient methane production. In addition, high ash biochar immersed in ash leachate further enhanced the reduction in methane production time.

Demand for biodiesel fuel is increasing from the perspective of a sustainable society, but the disposal of glycerin, which is a by-product of its production, has become an issue. However, it has been reported that when a very small amount of mixed sugar and glycerin are co-administered to anaerobic fermentation flora, glycerin is rapidly decomposed to produce valuable substances such as hydrogen. Glycerin is difficult to decompose due to its high water solubility and resistance to oxidation, and is not easily decomposed by a single bacterial lawn. Therefore, it was thought that the mixed sugar caused a drastic change in the structure of the complex flora. Focusing on this change in the bacterial flora, we attempted to induce similar changes using amino acids, which are low-molecular-weight organic substances similar to mixed sugars, and confirmed changes in the bacterial flora by 16S rRNA analysis in order to compare the functional genes and diversity. The purpose of this study is to identify the core bacteria that have changes in the microbiota, and to understand the dynamics of changes in the microbiota and anaerobic fermentation and to discover indicators.

In this study, in order to concentrate ammonium nitrogen (NH₄-N) in methane fermentation digestive fluid and to recycle it as nitrogen fertilizer, we attempted to concentrate NH₄-N in the digestive fluid by vacuum distillation with reference to the literature. Since digestive fluid contains substances other than NH₄-N, diluted ammonia water (simulated digestive fluid) was used to examine the experimental conditions. Evaporated NH₄-N was absorbed in distilled water or dilute sulfuric acid, or recovered by reaction with CO₂ were attempted. Vaporized NH₄-N was absorbed in distilled water or dilute sulfuric acid, or recovery by reaction with CO₂ was attempted, and the results were used in experiments with digestive fluid. The NH₄-N concentrations before and after the experiment were measured to confirm the amount of reduction. The amount of deposit was determined gravimetrically, and the composition was estimated using an infrared spectrophotometer. In experiments with simulated digestive fluid, the NH₄-N concentration decreased by 37-44%, and when CO₂ was introduced, ammonium carbonate was deposited by the reaction with vaporized ammonia. In experiments with digestive fluid, the NH₄-N concentration decreased by 37% at maximum, and ammonium carbonate was deposited even without the introduction of CO₂, and NH₄-N was concentrated and recovered as a solid.

Osaka Metropolitan University has been operating a biogas fermentation plant on campus for nearly 20 years. Although, its fermentation behavior had been verified by batch tests using minivials. It is difficult to screen various conditions with commercial-scale continuous facilities, and conversely, verification of continuous processing is difficult only with minivials. The purpose of the research was to compare the data of both methods and construct an experimental technique that can be easily scaled up for verification. Scale-up was evaluated by correlating hydraulic retention time (HRT) and inoculation rate of the batch test by artificially generating rancidity.

Methane fermentation has been attracting attention in recent years for the purpose of biomass volume reduction and energy recovery from biogas under anaerobic conditions, and can be classified into wet and dry types depending on the concentration of solids in the methane fermentation tank. Dry methane fermentation has advantages over wet methane fermentation, such as the ability to decompose waste without dilution, and vertical dry methane fermentation systems in particular have the advantage of being able to process a variety of waste-based biomass, including persistent waste such as waste paper. Vertical dry methane fermentation systems have not been widely used due to a lack of social implementation examples and data. Based on this background, Fuji Clean Co., Ltd. implemented Japan's first commercial-scale vertical dry methane fermentation system (manufactured by Kurita Water Industries Ltd.) in 2018, which is attached to an existing incineration facility. This study is a pioneering effort aimed at promoting the widespread use of vertical dry methane systems and evaluated the state of methane fermentation based on data obtained over a period of about three years starting in 2018.

In this study, anaerobic digestate pellets that slowly release nutrients into the sea were prepared for the purpose of fertilization of oligotrophic seas and utilization of anaerobic digestate. Three types of digestate (food, sewage, and livestock) and blast furnace cement were used as experimental materials to evaluate the nutrient release function of the digestate pellets and their effect on the growth of microalgae, which are primary producers in the sea. The results of nutrient leaching tests to artificial seawater showed that ammonium and phosphate ions were leached in large amounts from the digestate pellets in the sewage and livestock systems. Microalgae culture tests showed that the addition of digestate pellets from the sewage and livestock systems promoted the growth of the floating microalgae Nannochloropsis.oculata and the attached microalgae Nitzschia sp. These results suggest that digestate pellets may contribute to the fertility of oligotrophic waters.

Research was conducted on methods to improve the methane production efficiency for accelerting the implementation of anaerobic digestion systems. Accelerators are additives or carriers that improve the efficiency of methane production, such as fermentation aids and activated carbon. In recent years, it has been confirmed that biomethanation is promoted by applying voltage to anaerobic digesters, and the methane concentration in biogas is increased. Although studies have been conducted to confirm the improvement of methane production efficiency and to elucidate the mechanism by using each accelerator and voltage application alone, there has been no research to maximize the efficiency of anaerobic digestion by combining these accelerators and voltage applications. Therefore, this study aimed to maximize the fermentation efficiency of anaerobic digestion by combining each accelerator and voltage application, and to confirm the effect on methane production efficiency in anaerobic digestion system.

Food waste is an environmental problem. It is reported that food waste is a major component of urban solid waste. The amount of methane produced from food waste is higher than that of other substrates in terms of methane fermentation treatment methods. In methane fermentation, parameters are physicochemical and microbiological indicators to predict the state of the bioreactor. In this study, a high organic load shock was applied to a methane fermentation system using food waste as a substrate. By raising the organic load twice (twice as much each time), each parameter was continuously measured and recorded. Parameters include pH, ORP, VFA, arammoni concentration and biogas. Monitoring the parameter period 48h the changes of the parameters over time were observed and the relationship between the parameters was analyzed. Studies have shown that high organic loads increase the yield and rate of production of organic acids and change other parameters. This change has periodic laws and correlations between parameters.

The production of wastewater sludge on a global scale has seen a significant rise in recent years. As a result, there is an increasing focus on the development of efficient technologies for treating sludge. However, the treatment of biological organic waste presents challenges due to the complex nature of the waste and its constantly changing characteristics. To address these operational difficulties and enhance process control, the use of forecasting tools becomes essential. One effective tool that has emerged for modeling the entire waste treatment process is Artificial Neural Networks (ANNs). This study focused on a laboratory-scale continuous anaerobic digestion system to investigate methane production. To improve the prediction of methane production rate (MPR), Artificial Neural Networks (ANNs) were employed. The experiments were conducted in the lab-scale anaerobic digestion process and ANN modeling was utilized to forecast the MPR based on various influencing factors. These factors included influent concentration, Organic Loading Rate (OLR), pH, FOS (Fat, Oil, and Grease) content, and Total Alkalinity Concentration (TAC). The implemented ANN model successfully replicated the experimental data and accurately depicted the performance trends of the reactor, as demonstrated by its high R-value.

One of the manure treatment methods is anaerobic fermentation. This study investigated the selection of utilization methods for the biogas from the anaerobic fermentation in Kushiro, Hokkaido. Biomethane, hydrogen, and LPG were compared regarding the energy balance, value in the market, existing infrastructure, etc. As a result, LPG is preferred because the value in the market is relatively high, and the existing supply chain is available.

One method of utilizing digestate, a byproduct of methane fermentation, is to culture microalgae. The stage of collecting microalgae dispersed in the culture medium requires a lot of labor and energy. In this study, we focused on dialysis bags (bags made of dialysis membrane) to reduce the amount of culture solution to be processed, and decided to examine the possibility of culturing and recovering microalgae using dialysis bags.

Hydrogen sulfide is a toxic substance that is generated when organic matter containing sulfur decomposes. Landfills, which are waste management facilities, are a representative source of hydrogen sulfide emissions. Landfills emit high concentrations of hydrogen sulfide, which not only causes odor but also has corrosive properties, requiring control measures. However, since the sulfur (S) component within hydrogen sulfide molecules can be extracted and utilized as a high-value material, this study optimized the synthesis of a selective oxidation catalyst capable of extracting sulfur (S) component through selective oxidation of hydrogen sulfide. The study also examined the optimal coating method for scaling up the synthesized catalyst. Additionally, the study explored methods to improve the durability of the catalyst and achieve efficient extraction of sulfur. Through these efforts, the potential for controlling hydrogen sulfide and valorizing it was confirmed.

As a new recycling way for MAP (magnesium ammonium phosphate) recovered from sewage, effects of MAP fertilization on raising seedlings of eelgrass (Zostera marina) were studied for reproducing the seagrass bed as a hotspot of high bioproduction and biodiversity. In a biodegradable pot, 80 mL of silica sand and 10 seeds of eelgrass were placed and 0-200 mg of MAP was applied at 3-cm depth. As a closed circulation system, a 1.3-L plastic bottle contained these two sets, 1 L of artificial seawater, and a small pump. Germination ratio, leaf number, plant height, root length of eelgrass, nutrient concentrations of seawater, and oxidation-reduction potential (ORP) of sediment were measured for 100 days. As a result, the MAP application improved the germination ratio with a decrease in ORP, and nutrients eluted from MAP promoted the growth of eelgrass leaves. However, MAP application of >100 mg inhibited the eelgrass growth. It was supposed that the optimum MAP application for seedling eelgrass is 50 mg for 80 mL of silica sand.

There is an urgent need to promote the utilization of sewage sludge incineration ash as a phosphorus resource, because it contains P₂O₅ equivalent to phosphorus ore. Numerous tests have been conducted to utilize sewage sludge incineration ash as a phosphorus ore substitute in the current wet phosphoric acid refining processes. However, sewage sludge incineration ash contains more heavy metals (Cu, Zn, Pb, etc.) than phosphorus ore. The amount of sewage sludge incinerated ash that can be mixed is limited, because current wet phosphoric acid refining processes do not have a process to remove these impurities. The authors have proposed a method to selectively change certain oxide components into easily soluble or low-boiling salts and separate them by applying NH₄Cl to steelmaking slag and electric furnace dust generated in steel smelting. Based on these findings, we devised a method to reduce impurities (Cu, Zn, Pb, etc.) in sewage sludge incineration ash. In this presentation, the effects of ash/NH₄Cl ratio, temperature, and time were investigated according to the devised process to verify the possibility.

In order to clarify the mechanism by which the addition of a drying accelerator improves the drying rate of organic sludge, changes in the physical properties of sludge with the drying accelerator during drying is investigated. Since the drying rate of sludge increased most significantly during the reduced-rate drying period, changes in capillary attraction, which has the greatest influence on drying during the reduced-rate drying period, and evaluated the contact angle, which is a factor in the capillary attraction are focused on. In the experiment, 0.8 wt% of a drying accelerator was added to organic sludge, and the contact angles of the dried sludge samples were measured from mid-drying to complete drying. The contact angle of the sludge differed greatly depending on the type of drying accelerator. The contact angle of the sludge dried with the drying accelerator that promoted drying became larger, while the contact angle of the sludge dried with the drying inhibitor became smaller. Therefore, it was found that the drying promotion mechanism is likely that the larger contact angle reduces capillary attraction and weakens the ability to hold water inside the sludge, thereby preventing a significant decrease in the rate of water movement inside the sludge.

The non-ferrous smelting industry is accelerating its efforts to expand the processing of recycled materials in order to achieve carbon neutrality, but Top Submerged Lance (TSL) furnace, which play an important role as metal recycling furnace, consume large amounts of coal, which has high CO₂ emissions per unit of heat. The study examined waste circuit boards, waste plastics, waste tyres and biomass fuels as candidates for alternative fuels, and confirmed whether torrefaction of biomass fuels with low calorific value could produce the same calorific value as the fuel used, fuel coal. Sample properties and calorific value after torrefaction of six biomass fuels were compared with fuel coals, showed that all samples had a higher volatile content and a lower fixed carbon content than fuel coal, but the ash content differed from sample to sample. In addition, the torrefaction of both samples significantly increased the calorific value.

To stabilize the climate crisis, greenhouse gas(GHG) emissions should reach net-zero within decades. Achieving this requires the removal of atmospheric CO2 to offset the emissions that are difficult to eliminate. Among the various methods of carbon removal(biological, chemical, and geochemical), a large-scale land-based biological CO2 removal practice, such as carbon sequestration through biochar, is necessary. For this purpose, the quality standard for biochar should be first established by the government. Europe developed the European Biochar Certificate(use: soil carbon sequestration and material·products), a voluntary biochar industrial standard, and the United States formed the International Biochar Initiative, which is used internationally. For regulation, biochar is classified according to its use as general(organic carbon content and H/Corg ratio) and toxic(heavy metals etc.). The standard for each type needs to be established by the government, and only materials meeting the standard should be recognized as a GHG sink as per the GHG inventory of the Intergovernmental Panel on Climate Change. In a carbon market with further possibility for growth, only biochar that satisfies such certification standards must be exchanged during emission trading. Under these circumstances, the European Commission established a Carbon Removal Certification Regulation and proposed four certification criteria(quantification, additionality, long-term storage, and sustainability). In conclusion, a certification standard must be first set by the government before quantitatively identifying the contribution of biochar to carbon removal.

In two-phase anaerobic fermentation system, organic matter is used by hydrolytic bacteria in the first stage to produce VFAs and hydrogen, and methanogens in the second stage uses VFAs generated in the first stage and residual organic matter to produce methane. However, the activity of hydrolytic bacteria in the first stage is always inhibited due to the low pH value caused by the accumulation of VFAs without pH controlling. In this study, in order to make the system become stable by itself, the sludge in methane fermentation tank was recirculated into hydrogen fermentation tank which aimed to dilute substrate, provide alkalinity and microorganisms for hydrogen fermentation tank. By conducting two comparative experiments on whether sludge recirculation was added or not, it aimed to research the effect of sludge recirculation on gas generation capacity and organic matter degradation rate in each stage, and organic matter degradation efficiency of the whole system. Finally, the results showed that adding recirculation as the ratio of 1:1 could make system become stable by itself, improve generation rate (increased by 5.93% and 11.18% respectively) and yield (increased by 15.47% and 20.56% respectively) of hydrogen and methane and increase degradation efficiency of organic matter by 4%.