Faculty Profiles - FUJIWARA Takeshi

Papers - FUJIWARA Takeshi

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Assessment of solid waste collection system-A case study in Hai Chau district, Danang city, Vietnam Reviewed

Cuong Le Dinh, Song Toan Pham Phu, Takeshi Fujiwara, Tra Qui Phan

2022 7th International Scientific Conference on Applying New Technology in Green Buildings, ATiGB 2022 37 - 42 2022

Authorship：Last author Publishing type：Research paper (international conference proceedings)

Over the last decade, urgent problems related to the waste management system of Da Nang city have been recognized. Therefore, research on the current status of solid waste management system and solid waste collection system is gradually becoming paramount. This study applied Geographic Information System (GIS) and Global Positioning System (GPS) to study the current status of the waste collection system in Hai Chau district, Danang city. The GPS devices were utilized and in-depth interviews were also performed to collect information and data about the waste collection system. Data were synthesized, processed, and analyzed by QGIS 3.4 and Excel 2016. Four teams were in charge of solid waste collection in the entire Hai Chau district. The average daily amounts of solid waste collected were 56t (Team 1), 42.4t (Team 2), 42.6t (Team 3), and 61.1t (Team 4). The coverage ratios and physical duplication ratios of the three teams were 36.5% and 51.1% (Team 1), 55.6% and 47.1% (Team 2), 51.4% and 34.4% (Team 3). The compaction truck of Team 4 only transferred solid waste from transfer station to Khanh Son landfill. The problems and challenges of the solid waste collection system were also highlighted with recommendations for the outcomes.

DOI： 10.1109/ATiGB56486.2022.9984120

A Structure Analysis of Waste Classification Consciousness in Fu Yang, CHINA

DU Yuxin, TSUJII Hiroyuki, - Habuer, FUJIWARA Takeshi

Proceedings of the Annual Conference of Japan Society of Material Cycles and Waste Management 33 499 2022

Language：Japanese Publisher：Japan Society of Material Cycles and Waste Management

During the rapid socio-economic development of China, the amount of domestic waste has increased dramatically. Most areas collect domestic waste through mixed collection systems. The large number of informal landfill practices also results in significant loss of land resources, and they often lack adequate drainage management and are likely to contaminate soil and groundwater. One way to reduce informal landfill activities is to separate household waste. The purpose of this study was to determine the factors that determine residents' cooperation and intention to separate household waste. Based on the theory of planned behavior, a questionnaire survey was conducted among residents of Fuyang City, China, by collecting and analyzing existing studies and literature in the field of domestic waste sorting. The assumption put forward is that attitudes (A), subjective norms (SN), environmental perceptions (C), policy and publicity (PP), and perceived behavioral control (PBC), enhanced the behavioral intentions (I) of Fuyang residents toward domestic waste sorting. To assess this hypothesis, we analyzed the questionnaire data using SPSS AMOS 27, and the results showed that policy and publicity, environmental cognition, attitudes, and perceived behavior control were shown to positively influence the behavior intentions of the residents of Fu Yang city toward household waste classification.

DOI： 10.14912/jsmcwm.33.0_499

Home-Composting – A Study on the Simplicity of the System in the Application toward the Effectiveness and Feasibility in Spreading in Vietnam Reviewed

Pham Phu, Song Toan, Fujiwara, Takeshi, Nguyen, Duy Bao Dinh, Cuong Le

Chemical Engineering Transactions 89 505 - 510 2021.12

Authorship：Last author Language：English Publishing type：Research paper (scientific journal)

In 2018, the landfill in Danang city (DNC) received a significant amount of 1,073 t/d of waste, of which 54 % are bio-degradable waste, this lead to the overloaded of DNC landfill. It also shows the huge potential of composting using organic waste is being overlooked. This study aims at introducing a biowaste treatment with a conventional aerobic composting method, the T-COM V2.0 system. The model is a horizontal rotary drum with the same operating principle as the in-vessel composting system, with a capacity of 200 L, equivalent to 10 kg/d. Four models are alternately operated at DNC primary school for kitchen waste treatment, with the combination of effective microorganisms to improve decomposition efficiency and reduce odor. The Compost showed positive results with organic matter 2.5 times higher than the Vietnamese standard on organic fertilizer, odorless, non-contaminated by heavy metal, and can be applied for cultivation or improving soil condition. Within three months of operation, the system had shown efficiency impact with more than 1 t of organic waste treated and is possible to replicate at households, restaurants, hotels with outstanding features like technical assurance, economic optimization, operational simplification, and ease of application. Thus, this system can benefit the DNC waste management system by reducing the quantity of organic waste generation at source.

DOI： 10.3303/CET2189085

The response of anthropogenic mercury release in China to the Minamata Convention on Mercury: A hypothetical expectation Reviewed

Habuer, Takeshi Fujiwara, Masaki Takaoka

Journal of Cleaner Production 323 2021.11

Authorship：Last author Language：English Publishing type：Research paper (scientific journal)

The combination of anthropogenic activities and long-term atmospheric transport has resulted in a sustained increase in global mercury concentrations in air, in water and on land. The Minamata Convention on Mercury (MCM), is a global treaty with the goal of protecting human health and the environment from anthropogenic releases of mercury. This study aimed to quantify the mercury inputs and outputs in China in 2016–2019 according to five source categories and investigate the effect of an accelerated scenario/technology transformation required by the MCM on the subsequent distribution of mercury among environmental and intermediate reservoirs. Mercury releases to natural environment decreased dramatically after the MCM, such that around 840 t of mercury was released to those reservoirs in 2019, which is less than 21% of that in 2016 (1,063 t) when an accelerated scenario/technology transformation (STranf) was taken into consideration. Applying the accelerated STranf can hardly change the total release amount to the natural environment, also can reduce 53 t and 58 t of atmospheric emission in 2018 and 2019 respectively. Atmospheric emission was most sensitive to STranf, followed by emissions to land and water. This is the first attempt to provide a systematic evaluation of the effectiveness of the MCM based on the hypothetical expectations. As the MCM moves into the implementation phase, further information from scientific data and studies is critically needed to support decision-making and management. The results of this study can provide such information, facilitating the creation of strategic management policies for mercury as the MCM is implemented in China.

DOI： 10.1016/j.jclepro.2021.129089

The recyclable waste recycling potential towards zero waste cities - A comparison of three cities in China Reviewed

Binxian Gu, Xinyi Tang, Lingxuan Liu, Yuanyuan Li, Takeshi Fujiwara, Haohui Sun, Aijun Gu, Yanbing Yao, Ruiyang Duan, Jie Song, Renfu Jia

Journal of Cleaner Production 295 2021.5

Language：English Publishing type：Research paper (scientific journal)

Recycling is an essential practice for the successful operation of zero waste cities. It is essential to understand the recyclable waste recycling potential (RWRP). This study quantifies the RWRP of different cities in China. Suzhou, Yangzhou, and Suqian represent high-, middle- and low-income cities, respectively. The RWRP statistics are based on systematic multiple longitudinal tracking field surveys conducted between 2016 and 2019. Obvious RWRP spatio-temporal disparities were observed between inter-city and intra-city. For instance, Suzhou showed a slight increase in high resource value paper; Yangzhou had a slight increase in low resource value paper; and Suqian had a huge increase in no resource value paper and plastic. Additionally, more recyclable organics were generated in the old districts of Suzhou, and they were also predominant in the new districts of Yangzhou. No significant difference was observed in recyclable organics and recyclable material in Suqian. However, recyclable organics is a constant, while recyclable material fluctuates in the case cities. Household consumption structure has a major impact on RWRP. Other factors, such as economic development, urban resident population, consumption preferences, local customs and culture, as well as residential lifestyles also affect RWRP. This study proposes three policies: 1) to establish flexible and carefully planned recycling strategies, 2) to develop the distribution market of composting products, and 3) to incorporate economic and demographic initiatives to develop a workable recycling policy that can lead to zero waste implementation in the future. The zero waste concept was further assessed by the authors’ review of 69 cities worldwide based on previous research. We compared past results with the three featured cities in this study and 35 other Chinese cities, thereby presenting a world view of zero waste potential. It is anticipated that representative cities’ RWRP quantification and policy implementations can be a model for municipal solid waste management and recycling policies in other Chinese cities, which will help them transition to zero waste cities and probably provide a model for cities worldwide.

DOI： 10.1016/j.jclepro.2021.126358

Solid waste collection system in tourism destination – the status, problems and challenges Reviewed

Cuong Le Dinh, Takeshi Fujiwara, Misuzu Asari, Song Toan Pham Phu

Chemical Engineering Transactions 83 43 - 48 2021.2

Authorship：Last author Language：English Publishing type：Research paper (scientific journal)

Solid waste collection system (SWCS) plays an extremely important role in solid waste management system (SWMS). Optimization on SWCS have always been a primary mission of SWM towards sustainability. Hoi An city (HAC) is a tourist attraction in the central of Vietnam with omnipresence of tourism activities especially in tourism destination (TD). As a result, optimization of SWCS towards sustainability is crucial for TD of HAC. This study aimed to offer understandings on the current SWCS. This study was conducted with GPS (Global Positioning System) logger and QGIS 3.4 to collect and analyze data of existing SWCS. Results showed that, four modes of transportation were used for solid waste collection activities (SWCA) with almost all of sources of WG in the morning. Largest figures for total number of route (29) and amount of waste collected by carts (19.6m3) were illustrated in the morning shift (MS). Illegal solid waste collection (SWC) accounted for about 10 % of total amount of waste collected by carts. Forklift trucks were the final disposal of all SWCA in TD. Current waste gathering (WG) practices indirectly damaged the tourism activities while the improper implementation of selective waste collection at source hindered the efficiency of SWCS in TD. This study made a contribution as a scientific base for optimization and administration of SWCS.

DOI： 10.3303/CET2183008

Development of Disaster Waste Quantification Method using Mobile Mapping System Reviewed

吉川慶, 西山哲, 藤原健史

EICA 26 ( 2/3 ) 91 2021

Oyster shell as pH control substitute for two stage anaerobic co-digestion system Reviewed

Peni Astrini Notodarmojo, Takeshi Fujiwara, Habuer

Chemical Engineering Transactions 83 481 - 486 2021

Authorship：Last author Language：English Publishing type：Research paper (scientific journal)

Alkali substitute for two-stage anaerobic co-digestion system using kitchen waste, agriculture waste, and horse dung was compared with the standard alkali chemical used for pH control. The substitute used in this experiment is oyster shell waste. The study aims to investigate and evaluate the performance of oyster shells to overcome problems such as pH drops in the hydrolysis stage, greenhouse gas emission from chemical use, and methanogenesis stage performance such as methane gas yield and quality of biogas production. The result shows hydrolysate from control treatment using alkali has the highest volatile solid (VS) (1.18 %) and chemical oxygen demand (COD) (27.7 g/L). Oyster shell treatment has lower VS (1.14 %) and COD (25.01 g/L), but not significantly different from control. One-time oyster shell application can maintain reactor pH throughout the acid phase. Alkali treatment needs multiple doses to maintain the reactor in the intended pH range. At the end of the first stage, liquid hydrolysate pH value from alkali, oyster shell and no pH control treatment are 6.5, 5.29 and 3.8. As a result of comparing greenhouse gases emission in the cases of using NaOH as alkali, and oyster shell by Life Cycle Assessment (LCA) method, equivalent weight of CO2 emission from the oyster shell is lower by 0.0504 kg-CO2/kg-waste than that from alkali or only 0.15 times. In methanogenesis stage, alkali treatment produced 31 % higher methane gas yield (429.82 mL CH4/g VS in 1.64 g VS/L/d) compared to oyster shell treatment (321.32 mL CH4/g VS in 2.8 g VS/L/d). Methane gas yields of oyster treatment are stable through the different range of organic loading rate (OLR) while in alkali treatment the gas yield tends to increase in proportion with higher OLR. Highest methane gas percentage in biogas produced from alkali treatment (77.53 %), while in oyster shell treatment highest methane gas percentage is 71.11 %. Alkali treatment performs better in methane gas production using two stage anaerobic digesters, but oyster shells offer advantages in terms of practicality, stability and environmental impact.

DOI： 10.3303/CET2183081

Anthropogenic mercury release flow in China Reviewed

Habuer, Takeshi Fujiwara, Masaki Takaoka

Chemical Engineering Transactions 83 7 - 12 2021

Authorship：Last author Language：English Publishing type：Research paper (scientific journal)

China is the largest emitter of anthropogenic mercury worldwide. Implementation of the Minamata Convention on Mercury will significantly impact the development, use, and management of mercury resources. Chinese mercury management policies require significant adjustment. There is an urgent need to develop a current national mercury inventory to estimate mercury inputs and outputs by source category, and to clarify the distributions to various environmental scenarios. Here, the mercury releases are quantitatively analysed to facilitate the implementation of strategic mercury management policies in China. First, the mercury inputs and outputs by source categories in 2016 are quantified and then the mercury distributions to various environmental and intermediate sinks are estimated. The total mercury input was 5,116 t in 2016, of which 77 % was attributable to mineral production. In total, 3,083 t were released into various environmental and intermediate reservoirs. Of this total, 53.8 % was intentional uses, followed by extraction and combustion (26.5 %), and mineral production (19.6 %); 1,501 t were released into air, water, and land, of which extraction and combustion accounted for 48.6 % followed by mineral production (25.7 %) and intentional uses (25.6 %).

DOI： 10.3303/CET2183002

Analyzing the characterization of municipal solid waste in Da Nang City, Vietnam Reviewed

Song Toan Pham Phu, Takeshi Fujiwara, Naoya Akasaki, Dinh Cuong Le, Hoang Minh Giang, Pham van Dinh

Chemical Engineering Transactions 83 241 - 246 2021

Authorship：Last author Language：English Publishing type：Research paper (scientific journal)

Recently, most cities in Vietnam are facing waste problems that are mainly caused by the rapid increase of municipal solid waste (MSW) amount and the limitations of the MSW management system. This study aims to characterise the waste generation, composition and characteristics of MSW in Da Nang city, which is one of the five biggest cities in Vietnam. The current problems and challenges of MSW system are also analysed. The sampling survey was conducted in the dry and wet seasons in August and November 2018. The MSW was taken directly from trucks at the landfill site with the sample size by 500 kg/waste sources. This study shows that the simultaneous development of production, trade and service activities in the last decade has led to the speedy growth of waste by 9 %/y, and reached 1,073 t/d in 2018. In which, waste generated from industry and the hospitals account inconsiderable proportions by 3.9 % and 1.4 %. This study also indicated that the MSW generation rate from the urban areas is more than that of the coastal and industrial areas. For the composition of MSW, biodegradable waste and recyclables are the main components with the proportion of 54 % and 27 % of the total waste. While the waste composition almost do not differ considerably by seasons, the difference in the characteristics of waste is a consideration for the processing. The current problems and solutions to improve the MSW system toward sustainability are also discussed and suggested.

DOI： 10.3303/CET2183041

Life Cycle Impact Analysis of Anthropogenic Mercury Release in Malaysia Reviewed

Habuer, Muhamad Nabil Fikri Bin Abdul Hamid, Takeshi Fujiwara

Chemical Engineering Transactions 89 265 - 270 2021

Authorship：Last author Language：English Publishing type：Research paper (scientific journal)

Anthropogenic activities have aroused great concern in terms of the negative impact on ecosystems and human health. With rapid industrial development, Malaysia has experienced problems with regard to mercury pollution. Knowledge of the mercury emission and release inventory, and the main factors that ameliorate the environmental impact of anthropogenic activities, will contribute to environmentally sound mercury management, which is becoming increasingly urgent in Malaysia. In this study, inventories for total mercury emission and release in 2019 were devised to understand pollution sources. A life cycle impact assessment was used to identify the major factors contributing to the overall environmental burden. The environmental impact of anthropogenic mercury releases was compared between (sub)source categories. The total mercury input in 2019 was 36.4 t, of which 30.4 t were released to the natural environment under the output scenario of mercury release with no emission control. The respective amounts of 12.7, 1.8, and 15.9 t of mercury were released to air, water, and land. The environmental burden to terrestrial ecosystem imposed by mercury release was higher than that to freshwater and marine ecosystems. The harm to human health was 4,785 DALY, and harm to ecosystem was 0.85 species/y. The category of coal combustion was the largest contributor to the harms of human health (44 % of total impact), followed by cement production (11 % of total impact), and natural gas extraction and combustion (11 % of total impact). The category of gold mining (no amalgamation) was the largest contributor to the harms to ecosystems (76 % of total impact), followed by coal combustion (11 % of total impact). The result of this study can provide a scientific information to policymaker for strategic management of mercury in Malaysia.

DOI： 10.3303/CET2189045

Performance of Oyster Shell Powder Size on Methane Gas Generation in Two-Stage Anaerobic Digestion System Reviewed

Peni Astrini Notodarmojo, Takeshi Fujiwara, Habuer, Mochammad Chaerul

Chemical Engineering Transactions 89 373 - 378 2021

Authorship：Last author Language：English Publishing type：Research paper (scientific journal)

An anaerobic digester system is a sequence of process to digest biodegradable waste into biogas in the absence of oxygen. In two-stage anaerobic digestion system acid-forming steps or hydrolysis stage are separated from the methane forming steps. Although hydrolysis stage tends to get too acidic, addition of alkali substance can prevent pH from dropping too low so as to maintain good decomposition condition for microorganism. Oyster shell powder is a useful pH control additive containing CaCO3 at high percentage that can neutralize acid. In this study, the performances between industry-made fine oyster shell (IOS) powder (size 10.5 μm) and manually ground oyster shell (OS) powder (size < 1 mm) in methane generation yield were compared. NaOH, which is an alkali reagent for controlling pH, also used in comparison. The result showed that at the end of the hydrolysis stage, IOS powder increased pH up to 6.63, NaOH did almost the same (6.72), and OS powder was the lowest (6.1). In liquid residue, ratio of inorganic ash content with IOS treatment was the highest (2.1 %), but OS was the lowest (1.4 %). In the methanogenesis stage, CH4 concentration with NaOH treatment was the highest (80 %) compared to oyster shell powders: 74.33 % in IOS and 74.24 % in OS. Average methane yield over observation period of IOS treatment was the highest (533.9 mL/gVS), followed by alkali (487.3 mL/gVS) and OS (413.7 mL/gVS). Total CH4 from IOS treatment was 37 % and 8 % higher than OS and alkali treatment. Powder size of oyster shell greatly affected pH control, methane yield, and solid-liquid separation, but not methane concentration. Using IOS powder as pH control in hydrolysis of two-stage anaerobic system resulted in 78 % less cost than using NaOH.

DOI： 10.3303/CET2189063

Waste Segregation at Source and Separately Collection - The Inadequacy in Implementation in Vietnam Reviewed

Cuong Le Dinh, Takeshi Fujiwara, Song Toan Pham Phu

Chemical Engineering Transactions 89 499 - 504 2021

Authorship：Last author Publishing type：Research paper (scientific journal)

Hoi An city is a dynamic tourism city in Vietnam which had received the certificate of World Heritage Site by UNESCO. The boom in tourism activities led to problems for the solid waste management system. Solid waste collection activities account for the largest proportion of expenses on solid waste management. Optimization of the present solid waste collection system of Hoi An city is an urgent mission. This research is an effort to describe the current solid waste collection system of Hoi An city with the support of GIS and GPS. The results denoted Thursday, Friday, and Saturday accounted for the most enormous workload with 36, 34, and 40 trips. The total working time for these days were 103.86, 96.12, and 109.6 h while the total traveled distances were 733.76, 719.21, and 848.12 km. The complexity of solid waste collection routes, frequencies of solid waste collection, and coverage of solid waste collection activities decreased from urban areas to rural areas. Collection of waste accounted for the largest amount of time in solid waste collection activities. The low rate of waste separation at source, illegal solid waste collection, extreme weather, misbehaviours of drivers and workers, as well as the limitation in waste treatment facilities were the problems and challenges of the solid waste collection system in Hoi An city.

DOI： 10.3303/CET2189084

Environmental Impact of Anthropogenic Mercury Release in China Reviewed

Habuer, Takeshi Fujiwara, Masaki Takaoka

Chemical Engineering Transactions 89 301 - 306 2021

Authorship：Last author Language：English Publishing type：Research paper (scientific journal)

There is increasing public concern regarding the potential risks posed by mercury and mercury compounds. Knowledge of the mercury emission and release inventory, and determination of the main factors that ameliorate the environmental impact of anthropogenic activities, will contribute to environmentally sound mercury management. This study used a life cycle impact assessment to identify the major factors contributing to the overall environmental burden imposed by elemental mercury releases. The environmental impact of the business-as-usual scenario (total impacts = 5.13 GPt) was greater than that of the accelerated technology transformation (ACR) scenario (total impacts = 4.51 GPt), especially in terms of the impact on human health (HH). ACR mainly reduces mercury emissions to air, which affects HH. Compared to its effects on HH, mercury release to the environment has less impact on ecosystem diversity (ED). Mercury release to land had the largest impact on ED, followed by mercury emissions to air and discharge to water. ACR can reduce the harm to HH and marine ecosystems by 12 %. This study provides quantitative information on the environmental impact of mercury release, facilitating strategic management of mercury emissions in line with the Minamata Convention on Mercury (implemented in China in 2017).

DOI： 10.3303/CET2189051

Comparison Between Single and Two-Stage Anaerobic Digestion of Vegetable Waste: Kinetics of Methanogenesis and Carbon Flow Reviewed

Dinh Pham Van, Fujiwara Takeshi, Giang Hoang Minh, Song Toan Pham Phu

Waste and Biomass Valorization 11 ( 11 ) 6095 - 6103 2020.11

Language：English Publishing type：Research paper (scientific journal)

Abstract: This study aims to compare the performance and kinetics between the single-stage anaerobic digestion (SAD) and the two-stage anaerobic digestion (TAD) of vegetable waste (VW). The SAD was performed using continuously stirred tank reactors. Meanwhile, the TAD experiment was set up using a combined system involving a continuously stirred tank for hydrolysis/acidogenesis and an upflow reactor for methanogenesis. The hydrolytic reactor operated as a batch process with a retention time (RT) of 9 days, while the methane reactor was a continuous process operation with RT of 20 days. Both TAD and SAD were controlled at a temperature of 36 °C. The SAD experiments lasted for 143 days, and were characterised by the kinetic rate constant k = 0.02 day−1 which was much lower than that for the TAD (k = 0.66 − 2.16 day−1). The SAD seemed to be inhibited by high concentration of free ammonia and low inoculum to substrate ratio; herein, only 17.8–22.3% of the initial carbon could be converted into biogas (equivalent to 91–110 Nml/g-VSadded) with low methane content (44.1–48.7%). Meanwhile, TAD converted 41.67% initial carbon to biogas (equivalent to 299.0–374.6 Nml/g-VSadded) with high methane content (71.68–81.0%). Moreover, methanogenesis in the TAD was highly stable which enabled the digestion process to return to normal state within a few days, even though the concentrations of the influent increased to double (6.5–24.5 g-COD/l). As per these results, the TAD was much more stable, faster, and stronger than the SAD. Graphic Abstract: [Figure not available: see fulltext.]

DOI： 10.1007/s12649-019-00861-0

Enhancing waste management practice - The appropriate strategy for improving solid waste management system in Vietnam towards sustainability Reviewed

Song Toan Pham Phu, Takeshi Fujiwara, Giang Minh Hoang, Dinh Van Pham, Hoa Kieu Thi, Yen Anh Tran Thi, Cuong Dinh Le

Chemical Engineering Transactions 78 319 - 324 2020.2

Language：English Publishing type：Research paper (scientific journal)

This study aims to build the appropriate model of waste management practice (WMP) towards sustainable municipal solid waste (MSW) system in a city of developing country like Vietnam. A waste audit was performed and material flow analysis method was simulated to describe and analyse the current status of MSW system and its assumpted models. Four WMP models were built based on the feature of the region, the intention and optimisation of WMP, and the consensus of the government. This study shows that the improvement of the SWM system can reduce a significant amount of waste to landfill. Notably, the waste reduction performance is 5.0, 7.8, 11.11 and 29.3 % in S1, S2, S3 and S4, respectively. Also, the recovery performance of recyclables changes in proportional to the level of SWM practice and reach at 3.78, 5.843, 4.593, and 7.120 t/d, respectively. This study reveals that the improvement of SWM practice at source from intentional to optimal rate is the sustainable strategy for developing an SWM system in Hoi An City.

DOI： 10.3303/CET2078054

A review of anaerobic digestion systems for biodegradable waste: Configurations, operating parameters, and current trends Reviewed

Dinh Pham Van, Takeshi Fujiwara, Bach Leu Tho, Pham Phu Song Toan, Giang Hoang Minh

Environmental Engineering Research 25 ( 1 ) 1 - 17 2020.2

Language：English

With benefits to the human health, environment, economy, and energy, anaerobic digestion (AD) systems have attracted remarkable attention within the scientific community. Anaerobic digestion system is created from (bio)reactors to perform a series of bi-metabolism steps including hydrolysis/acidogenesis, acetogenesis, and methanogenesis. By considering the physical separation of the digestion steps above, AD systems can be classified into single-stage (all digestion steps in one reactor) and multi-stage (digestion steps in various reactors). Operation of the AD systems does not only depend on the type of digestion system but also relies on the interaction among growth factors (temperature, pH, and nutrients), the type of reactor, and operating parameters (retention time, organic loading rate). However, these interactions were often reviewed inadequately for the single-stage digestion systems. Therefore, this paper aims to provide a comprehensive review of both single-stage and multi-stage systems as well as the influence of the growth factors, operating conditions, and the type of reactor on them. From those points, the advantages, disadvantages, and application range of each system are well understood.

DOI： 10.4491/eer.2018.334

Waste-to-landfill reduction: Assessment of cost-effective solutions using an optimisation model Reviewed

Giang Minh Hoang, Song Toan Pham Phu, Takeshi Fujiwara, Dinh Van Pham

Chemical Engineering Transactions 78 511 - 516 2020

Language：English Publishing type：Research paper (scientific journal)

Significant increases in solid waste generation and inappropriate waste management system leads to overloaded landfills, which have negative impacts on the environment and human health. Reducing waste sent to landfill has become an emerging mission in Vietnam. This study aims at assessing cost-effective solutions to reduce waste-to-landfill amount using system analysis approach. A single-objective optimisation model is formulated to minimise the cost of the system in association with different landfill waste reduction targets and values of waste separation efficiency for Hoi An city. As a result, the landfill target is directly proportional to the cost. It means the higher landfill reduction target leads to the higher cost of the system. Meanwhile, the separation efficiency is inversely proportional to the system cost. The result showed that twenty-five percent of municipal waste treated in landfills is achievable target based on the current condition of the city. Also, ten percent of municipal waste sent to landfill is an infeasible mission if the waste separation rate is too low. If waste is wholly separated at source, incineration, composting and landfill can be applied as main treatment alternatives to reduce seventy-five percent of municipal waste sent to landfill with the cost of about 1,800 USD/d.

DOI： 10.3303/CET2078086

Solid waste management practice in a tourism destination – The status and challenges: A case study in Hoi An City, Vietnam Reviewed

Song Toan Pham Phu, Takeshi Fujiwara, Giang Hoang Minh, Dinh Pham Van

Waste Management and Research 37 ( 11 ) 1077 - 1088 2019.11

Authorship：Last author Publishing type：Research paper (scientific journal)

This study aims to present waste characterisation, solid waste management practice and analyse the challenges in the solid waste management system in the tourism destination of Hoi An City, Vietnam. The sampling and questionnaire surveys were conducted for measuring characterisation and management practice of solid waste. A material flow analysis method was used for analysing the waste flow. The results show that the tourism destination generated daily around 15080 kg t of waste, in which the significant proportions come from restaurants (46%), hotels (22%) and households (13%). The feature of the waste composition is high rates of kitchen waste (46.8%), tissue (11.54%) and recyclable materials (12.58%), which result in high moisture (46.79%) and a low heating value (16,866 kJ kg-1) of waste. Also, solid waste management practices were evasively implemented by stakeholders with low rates and efficiency. Furthermore, a substantial gap of the solid waste management system is the confusion in waste collection activities, which is shown by the overload of waste in street bins and the financial loss for the solid waste management system owing to the non-compliance with collection regulation of stakeholders. Also, the mixing of waste by collection crews after separation at sources, the in-appropriation of collection time and manner are the dark points of the solid waste management system that may be causes of the non-cooperation of stakeholders. These gaps and confusion in the solid waste management system are the significant challenges in the improvement of the solid waste management system in the tourism destination toward sustainability.

DOI： 10.1177/0734242X19862042

Sustainable solid waste management system using multi-objective decision-making model: a method for maximizing social acceptance in Hoi An city, Vietnam Reviewed

Giang Minh Hoang, Takeshi Fujiwara, Toan Song Pham Phu, Luong Duc Nguyen

Environmental Science and Pollution Research 26 ( 33 ) 34137 - 34147 2019.11

Publishing type：Research paper (scientific journal)

The main aim of this study was to develop a decision support system for sustainable municipal solid waste management (MSWM) in Hoi An city (HAC), Vietnam. A face-to-face interview was conducted with local experts including authorities, citizens, waste collection contractors and recyclers to identify main objectives of waste management system and appropriate treatment methods. A multi-objective optimization model was proposed using non-linear programming approach. An interactive method known as reference point method (RPM) was applied for solving the problem with three objectives including cost minimization, landfill minimization and emission minimization. As a result, the efficient waste-flow-allocation and the optimal capacity of disposal facilities were determined by intense discussion and agreement among decision-makers. Waste incineration, anaerobic digestion, sanitary landfill and current recycling activities should be applied with a cost of about 2300 US$ daily. Also, the daily emission of various pollutants was about 35 metric tons, and the greenhouse gas (GHG) is 313 tons CO2-eq.

DOI： 10.1007/s11356-018-3498-5

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