Global Research Progress on Municipal Waste and Future Prospect Based on the Cross-national Comparisons

Due to the acceleration of urbanization,the municipal waste(MW)problem has transformed into a global challenge for urb-an sustainability.To elucidate historical trends,current focal points,and future directions in MW research,we conducted a bibliometric analysis and employed knowledge graph visualization to scrutinize a total of 34212 articles,which were published between 1991 and 2021 in the Web of Science(WoS)core database.The results indicated that current major research themes encompass waste classifica-tion and recycling,waste management and public behavior,waste disposal methods and technologies,as well as environmental impact and evaluation.There has been a shift in the research focus from the environmental impacts of waste incineration to sustainable manage-ment related issues.A comparison of research from six typical countries revealed the differences in research priorities and techniques advantages.Scholars from the USA and Britain initiated MW research earlier than other countries and investigated management issues in depth,such as public behavior and willingness to pay.Meanwhile,Japanese,German,and Swedish scholars conducted extensive studies on advanced waste treatment technologies,such as disposal and recycling,risk assessment,and waste-to-energy techniques.Chinese scholars placed particular emphasis on end-of-pipe treatments and their associated environmental impacts.Hotspots and poten-tial future frontiers were identified by burst detection analysis.Keywords with high value of burst index(BI)worldwide are food waste and circular economy.Chinese scholars have put great efforts on waste environmental impact and its recycling technologies,while we’re expecting to further investigating vulnerable population.Furthermore,this study contributes to bridging the regional gap of scientific research among different countries and fostering international collaboration.

Anaerobic Co-digestion Process Efficiency Estimation in Phases as an Alternative for Municipal Waste Treatment

The incorrect disposal of the waste generated in the municipalities contributes to water and soil contamination,resulting in a real concern in order to find an adequate disposal as well as obtain by-products that can be used to reduce CO2 emissions.Anaerobic digestion turns out to be the most efficient treatment,both in environmental and economic terms.The objective of this study is to evaluate the anaerobic co-digestion process in phases as an alternative for the treatment of municipal waste:sludge from water treatment plants and the biodegradable part of Municipal Solid Waste(MSW),for three HRTs(Hydraulic Retention Times).Testing results show up a max elimination of 70.68%in VS(Volatile Solids)and 74.01%in COD(Chemical Oxygen Demand).With these percentages of elimination on average,15.96 L/d of biogas was produced,for each kg of COD eliminated 0.56 m3 of biogas was produced and for each kg of SV 0.85 m3 and methane of 50.10%.

HVAC Design Strategies for Municipal Waste Incineration Power Plants

In recent years,relevant government departments have achieved the goal of reduction and harmless application through the development and implementation of municipal waste incineration power plants,in order to advocate ecological and environmental protection.At present,in order to further achieve the goal of sustainable development,municipal waste incineration power plants have actively responded to the national call and requirements as well as made overall arrangements for the energy-saving design and optimization design of their internal system.Therefore,with the concept of sustainable development,this paper studies and analyzes the problems of the HVAC design as well as suggests related strategies for municipal waste incineration power plants in order to provide relevant reference.

Model Prediction and Optimal Control of Gas Oxygen Content for A Municipal Solid Waste Incineration Process

In the municipal solid waste incineration process,it is difficult to effectively control the gas oxygen content by setting the air flow according to artificial experience.To address this problem,this paper proposes an optimization control method of gas oxygen content based on model predictive control.First,a stochastic configuration network is utilized to establish a prediction model of gas oxygen content.Second,an improved differential evolution algorithm that is based on parameter adaptive and t-distribution strategy is employed to address the set value of air flow.Finally,model predictive control is combined with the event triggering strategy to reduce the amount of computation and the controller's frequent actions.The experimental results show that the optimization control method proposed in this paper obtains a smaller degree of fluctuation in the air flow set value,which can ensure the tracking control performance of the gas oxygen content while reducing the amount of calculation.

Forecasting the Municipal Solid Waste Using GSO-XGBoost Model

Waste production rises in tandem with population growth and increased utilization.The indecorous disposal of waste paves the way for huge disaster named as climate change.The National Environment Agency(NEA)of Singapore oversees the sustainable management of waste across the country.The three main contributors to the solid waste of Singapore are paper and cardboard(P&C),plastic,and food scraps.Besides,they have a negligible rate of recycling.In this study,Machine Learning techniques were utilized to forecast the amount of garbage also known as waste audits.The waste audit would aid the authorities to plan their waste infrastructure.The applied models were k-nearest neighbors,Support Vector Regressor,ExtraTrees,CatBoost,and XGBoost.The XGBoost model with its default parameters performed better with a lower Mean Absolute Percentage Error(MAPE)of 8.3093(P&C waste),8.3217(plastic waste),and 6.9495(food waste).However,Grid Search Optimization(GSO)was used to enhance the parameters of the XGBoost model,increasing its effectiveness.Therefore,the optimized XGBoost algorithm performs the best for P&C,plastics,and food waste with MAPE of 4.9349,6.7967,and 5.9626,respectively.The proposed GSO-XGBoost model yields better results than the other employed models in predicting municipal solid waste.

Prediction of NO_(x)concentration using modular long short-term memory neural network for municipal solid waste incineration

Air pollution control poses a major problem in the implementation of municipal solid waste incineration(MSWI).Accurate prediction of nitrogen oxides(NO_(x))concentration plays an important role in efficient NO_(x)emission controlling.In this study,a modular long short-term memory(M-LSTM)network is developed to design an efficient prediction model for NO_(x)concentration.First,the fuzzy C means(FCM)algorithm is utilized to divide the task into several sub-tasks,aiming to realize the divide-and-conquer ability for complex task.Second,long short-term memory(LSTM)neural networks are applied to tackle corresponding sub-tasks,which can improve the prediction accuracy of the sub-networks.Third,a cooperative decision strategy is designed to guarantee the generalization performance during the testing or application stage.Finally,after being evaluated by a benchmark simulation,the proposed method is applied to a real MSWI process.And the experimental results demonstrate the considerable prediction ability of the M-LSTM network.

Assessing the Factors Influencing Effective Municipal Solid Waste Management System in Barishal Metropolitan Areas

Unorganized municipal solid waste (MSW) disposal system leads to stress on ecosystems and disturbs various nature cycles and human health. Solid waste management all over world is looked as a major challenge to civil bodies, especially in developing countries like Bangladesh. The proper management system of municipal solid waste depends on various factors like social, cultural, financial, political, environmental, physical and institutional and so on. The purpose of this study is to explore the leading factors that affect the solid waste management in Barishal city. For achieving this purpose, this research first has identified the socio-economic, cultural, physical and technical, institutional and environmental factors and then analyzed the factors which affect the solid waste management system in the study area. To achieve the purpose of the study, quantitative method has been used in this research. As a sample of this study, 150 household heads from total household members of the city have been selected randomly by using lottery method. A structured questionnaire has been constructed for collecting quantitative data. The quantitative data have been analyzed in this study by using SPSS Program, and Microsoft Excel. The findings of the study show that all city people know solid waste and solid waste management stakeholders present in the city and waste pickers collect all types of waste in the city and socio-economic, cultural, physical and technical, institutional factors affect the effective solid waste management in the study area where environmental factors have no influence on effective solid waste management in the study area. The study people have a bad impression of the current existing management system of the solid waste and they express their expectations where they mention that if municipal authorities improve the condition of the infrastructure, roads and vehicles;allow more budgets to manage waste;take proper strategies and planning to manage waste smartly like imposing fines, set up rules, then the municipal authorities will be able to manage solid waste properly. Finally, this research has proposed some recommendations that might be helpful for the policy-makers in the study area for making policies and further research regarding solid waste management.

Bird’s-eye view of recycled solid wastes in road engineering

Recent trends in road engineering have explored the potential of incorporating recycled solid wastes into infrastructures that including pavements,bridges,tunnels,and accessory structures.The utilization of solid wastes is expected to offer sustainable solutions to waste recycling while enhancing the performance of roads.This review provides an extensive analysis of the recycling of three main types of solid wastes for road engineering purposes:industrial solid waste,infrastructure solid waste,and municipal life solid waste.Industrial solid wastes suitable for road engineering generally include coal gangue,fly ash,blast furnace slag,silica fume,and steel slag,etc.Infrastructure solid wastes recycled in road engineering primarily consist of construction&demolition waste,reclaimed asphalt pavements,and recycled cement concrete.Furthermore,recent exploration has extended to the utilization of municipal life solid wastes,such as incinerated bottom ash,glass waste,electronics waste,plastic waste,and rubber waste in road engineering applications.These recycled solid wastes are categorized into solid waste aggregates,solid waste cements,and solid waste fillers,each playing distinct roles in road infrastructure.Roles of solid waste acting aggregates,cements,and fillers in road infrastructures were fully investigated,including their pozzolanic properties,integration effects to virgin materials,modification or enhancement solutions,engineering performances.Utilization of these materials not only addresses the challenge of waste management but also offers environmental benefits aiming carbon neutral and contributes to sustainable infrastructure development.However,challenges such as variability in material properties,environmental impact mitigation,secondary pollution to environment by leaching,and concerns regarding long-term performance need to be further addressed.Despite these challenges,the recycled solid wastes hold immense potential in revolutionizing road construction practices and fostering environmental stewardship.This review delves into a bird’seye view of the utilization of recycled solid wastes in road engineering,highlighting advances,benefits,challenges,and future prospects.

Current Situation Analysis and Suggestions for Solid Waste Management Practices among Households in Freetown

Freetown which is the capital city of Sierra Leone is facing challenges with population growth, urbanization, and industrialization, leading to an increase in municipal solid waste (MSW) generation. The study aims to evaluate MSW generation, composition, and disposal methods, as well as the impact of collection fees, policy implementation, and women’s participation in municipal solid waste management (MSWM). The study used both qualitative and quantitative methods for data collection and analysis. The study administered 393 structured questionnaires in three selected sections to collect data on variables such as family size, education, level of knowledge, etc. The study used door-to-door data collection to determine the rate of solid waste generation, composition, and disposal in 66 households from two of the selected sections and 34 households from the other section to evaluate the current situation of MSWM practices among households in Freetown. The study used a descriptive statistic to analyze the data collected using Origin-Pro9 and MS Excel software. The findings showed that with a 4.2% urban growth rate, Freetown had a population of 1,467,543 in 2023, generating 851 tons of MSW per day, with organic waste accounting for 78% of the total MSW generated. Plastic waste generation also increased from 7.6% in 2020 to 13% in 2023. The study emphasizes the need to sustain the MSWM system by prioritizing solid waste collection fees, policy enforcement, and women’s participation in the MSWM sector. It further suggests and provides recommendations for developing an efficient and sustainable MSWM system in Sierra Leone, including knowledge transfer from countries like China and the US.

A new complex plant for carbonization and composting of municipal wastes

A new complex plant for carbonization and composting of municipal wastes proposed for Gero City is introduced. The separated combustible waste and non-separated combustible waste are carbonized in two fluidized carbonization furnaces in the plant, and the coke produced is used in steelworks. The separated garbage and forest-wastes are mixed with dried septic-tank sludge to produce high quality compost for farms. This use of waste materials in the complex plant considerably lowers the amount of waste going to land-fills, and in addition, creates lower total emission of dioxins and carbon dioxide into the environment.

Release of volatile organic compounds during bio-drying of municipal solid waste

Three treatments were tested to investigate the release concentrations of volatile organic compounds （VOCs） during the bio-drying of municipal solid waste （MSW） by the aerobic and combined hydrolytic-aerobic processes.Results showed that VOCs were largely released in the first 4 days of bio-drying and the dominant components were：dimethyl disulfide,dimethyl sulfide,benzene,2-butanone,limonene and methylene chloride.Thus,the combined hydrolytic-aerobic process was suggested for MSW bio-drying due to fewer aeration quantities in this phase when compared with the aerobic process,and the treatment strategies should base on the key properties of these prominent components.Malodorous sulfur compounds and terpenes were mainly released in the early phase of bio-drying,whereas,two peaks of release concentrations appeared for aromatics and ketones during bio-drying.Notably,for the combined hydrolytic-aerobic processes there were also high concentrations of released aromatics in the shift from hydrolytic to aerobic stages.High concentrations of released chlorinateds were observed in the later phase.For the VOCs produced during MSW bio-drying,i.e.,malodorous sulfur compounds,terpenes and chlorinateds,their release concentrations were mainly determined by production rates;for the VOCs presented initially in MSW,such as aromatics,their transfer and transport in MSW mainly determined the release concentrations.

Biodrying of municipal solid waste with high water content by combined hydrolytic-aerobic technology

The high water content of municipal solid waste(MSW)will reduce the effciency of mechanical sorting,consequently unfavorable for beneficial utilization.In this study,a combined hydrolytic-aerobic biodrying technology was introduced to remove water from MSW.The total water removals were proved to depend on the ventilation frequency and the temporal span in the hydrolytic stage. The ventilation frequency of 6 times/d was preferable in the hydrolytic stage.The hydrolytic span should not be prolonged more than ...

Solidification of Municipal Solid Waste Incineration FlyAsh with Cement and Its Leaching Behaviors of Heavy Metals

The solidifying effect of cement addition on municipal solid waste incineration fly ash (MSWFA for short,collected from the gas exhaust system of MSW incinerator),the interaction of MSWFA with cement and water and the leaching of heavy metals from cement solidified MSWFA are investigated.The main results show that:(1) when MSWFA is mixed with cement and water,H 2 evolution,the formation and volume expansion of AFt will take place,the volume expansion can be reduced by ground rice husk ash addition;(2) heavy metals do leach from cement solidified MSWFA and at lower pH more leaching will occur;(3) compared with cement-solidified fly ash,the leachate of solidified MSWFA is with higher heavy metal contents;(4) with the increment of cement addition leached heavy metals are decreased;and (5) concentrations of Zn,Mn,Cu and Cd in all the leachates can meet the relevant Standards of Japan,but as the regulations for soil and groundwater protection of Japan are concerned,precautions against the leaching of Pb,Cl - and Cr 6+ and so on are needed.

Chemical speciation and mobility of heavy metals in municipal solid waste incinerator fly ash

Chemical speciation is a significant factor that governs the toxicity and mobility of heavy metals in municipal solid waste incinerator fly ash. Sequential extraction procedure is applied to fractionate heavy metals(Pb, Zn, Cd, Cu, and Cr) into five defined groups: exchangeable, carbonate, Fe-Mn oxide, organic, and residual fractions. The mobility of heavy metals is also investigated with the aid of toxicity characteristic leaching procedure. In the fly ash sample, Pb is primarily presented in the carbonate(51%) and exchangeable(20%) fractions; Cd and Zn mainly exist as the exchangeable(83% and 49% respectively); Cu is mostly contained in the last three fractions(totally 87%); and Cr is mainly contained in the residual fraction(62%). Pb, Zn and Cd showed the high mobility in the investigation, thus might be of risk to the natural environment when municipal solid waste incinerator fly ash is landfilled or reutilized.

Characteristics of gaseous product from municipal solid waste gasification with hot blast furnace slag

Possibility of combustible gas production from municipal solid waste （MSW） using hot blast furnace （BF） slag has been studied.The objective of this work is to generate combustible gas from MSW using heated BF slag.In this experiment,the thermal stability of the MSW was analyzed by thermogravimetric analysis,and effects of temperature,gasifying agent （air,N2,steam） and BF slag on the gas products were investigated at 600？900 ？C.The thermogravimetric analysis indicates that the weight loss of MSW includes four stages：evaporation of the moisture,combustion of volatile materials,burning of carbon residue and burnout of ash.The contents of the combustible gas increase with increasing temperature,and the lower calorific value （LCV） increases rapidly at 600？900 ？C.It is found that volume fraction of CO,H2 and CH4 at different atmospheres increases in the order N2〈air〈steam.It is believed that BF slag acts as the catalyst and the heat carrier,which promotes the gasification reactivity of MSW.

Environmental monitoring and fuzzy synthetic evaluation of municipal solid waste transfer stations in Beijing in 2001-2006

Transfer station(TS)is an integral part of present-day municipal solid waste(MSW)management systems.To provide information for the incorporation of waste facilities within the current integrated waste management system,the authors measured the existing environmental quality at five MSW TSs.Discharged wastewater,air,and noise were monitored and assayed at the five TSs in Beijing in 2001-2006 during rainy seasons(RSs)and dry seasons(DSs).Except Ammonia(NH_3)and hydrogen sulfide(H_2S),the analytical results of...

Influence of temperature on performance of anaerobic digestion of municipal solid waste

The influence of temperature on the performance of anaerobic reactors for treating the organic fraction of municipal sohd waste （OFMSW） was studied. Batch digestion of OFMSW was carded out for 32 d at different temperature （25℃, 35℃, 45℃ and 55℃） conditions for total solid concentrations （TS） 17% with the ratio of total organic carbon to nitrogen （C/N） being, 25：1 respectively, while keeping other parameters constant such as inoculum, start-up pH, reactor volume （2 L） and so on. Temperature can influence the methanogenic bacteria activity, accordingly inhibiting the OFMSW biodegradation and stabilization efficiency. Anaerobic reactors excelled at TS reduction, total volatile solid reduction, chemical oxygen demand reduction, increasing cumulative biogas production, whose rate was at temperature （35℃ and 55℃） conditions. Methane concentration in the biogas was above 65% in four reactors. In addition, the fluctuation of temperatures resulted in the biogas production variation. The data obtained indicated that temperature had a significant influence on anaerobic process.

Volatilization of heavy metals during incineration of municipal solid wastes

Incineration experiments with MSW, which had been impregnated with heavy metals, were presented to obtain information on the volatilization behavior of the elements cadmium(Cd), lead(Pb), and zinc(Zn) under different conditions. Experiments were carried out in a bubbling fluid bed system connected to a customized inductively coupled plasma optical emission spectroscopy(ICP-OES) for analyzing metals in the flue gas. The results indicated that the combustion temperature, the gas atmosphere, and the chlorine content in the flue gas could affect the volatilization behavior of heavy metals. In the fluidized bed combustion, a large surface area was provided by the bed sand particles, and they may act as absorbents for the gaseous ash-forming compound. Comparer with the metals Cd and Pb, the vaporization of Zn was low. The formation of stable compounds such as ZnO·Al 2O 3 could greatly decrease the metals volatilization. The presence of chlorine would enhance the volatilization of heavy metals by increasing the formation of metal chlorides. However, when the oxygen content was high, the chlorinating reaction was kinetically hindered, which heavy metals release would be delayed.

Engineering properties for high kitchen waste content municipal solid waste

Engineering properties of municipal solid waste （MSW） depend largely on the waste＇s initial compositionand degree of degradation. MSWs in developing countries usually have a high kitchen waste content（called HKWC MSW）. After comparing and analyzing the laboratory and field test results of physicalcomposition, hydraulic properties, gas generation and gas permeability, and mechanical properties forHKWC MSW and low kitchen waste content MSW （called LKWC MSW）, the following findings wereobtained： （1） HKWC MSW has a higher initial water content （IWC） than LKWC MSW, but the field capacitiesof decomposed HKWC and LKWC MSWs are similar; （2） the hydraulic conductivity and gaspermeability for HKWC MSW are both an order of magnitude smaller than those for LKWC MSW; （3）compared with LKWC MSW, HKWC MSW has a higher landfill gas （LFG） generation rate but a shorterduration and a lower potential capacity; （4） the primary compression feature for decomposed HKWCMSW is similar to that of decomposed LKWC MSW, but the compression induced by degradation ofHKWC MSW is greater than that of LKWC MSW; and （5） the shear strength of HKWC MSW changessignificantly with time and strain. Based on the differences of engineering properties between these twokinds of MSWs, the geo-environmental issues in HKWC MSW landfills were analyzed, including highleachate production, high leachate mounds, low LFG collection efficiency, large settlement and slopestability problem, and corresponding advice for the management and design of HKWC MSW landfills wasrecommended.

Minimizing N2O fluxes from full-scale municipal solid waste landfill with properly selected cover soil

Municipal solid waste landfills emit nitrous oxide （N2O） gas. Assuming that the soil cover is the primary N2O source from landfills, this study tested, during a four-year project, the hypothesis that the proper use of chosen soils with fine texture minimizes N2O emissions. A full-scale sanitary landfill, a full-scale bioreactor landfill and a cell planted with Nerium indicum or Festuca arundinacea Schreb, at the Hangzhou Tianziling landfill in Hangzhou City were the test sites. The N2O emission rates from all test sites were considerably lower than those reported in the published reports. Specifically, the N2O emission rate was dependent on soil water content and nitrate concentrations in the cover soil. The effects of leachate recirculation and irrigation were minimal. Properly chosen cover soils applied to the landfills reduced N2O flux.