Optimal planning for the sustainable utilization of municipal solid waste

The increasing generation of municipal solid waste (MSW) is a major problem particularly for large urban areas with insufficient landfill capacities and inefficient waste management systems. Several options associated to the supply chain for implementing a MSW management system are available, however to determine the optimal solution several technical, economic, environmental and social aspects must be considered. Therefore, this paper proposes a mathematical programming model for the optimal planning of the supply chain associated to the MSW management system to maximize the economic benefit while accounting for technical and environmental issues. The optimization model simultaneously selects the processing technologies and their location, the distribution of wastes from cities as well as the distribution of products to markets. The problem was formulated as a multi-objective mixed-integer linear programing problem to maximize the profit of the supply chain and the amount of recycled wastes, where the results are showed through Pareto curves that tradeoff economic and environmental aspects. The proposed approach is applied to a case study for the west-central part of Mexico to consider the integration of MSW from several cities to yield useful products. The results show that an integrated utilization of MSW can provide economic, environmental and social benefits.     

Eco-efficiency for greenhouse gas emissions mitigation of municipal solid waste management: a case study of Tianjin, China

The issue of municipal solid waste (MSW) management has been highlighted in China due to the continually increasing MSW volumes being generated and the limited capacity of waste treatment facilities. This article presents a quantitative eco-efficiency (E/E) analysis on MSW management in terms of greenhouse gas (GHG) mitigation. A methodology for E/E analysis has been proposed, with an emphasis on the consistent integration of life cycle assessment (LCA) and life cycle costing (LCC). The environmental and economic impacts derived from LCA and LCC have been normalized and defined as a quantitative E/E indicator. The proposed method was applied in a case study of Tianjin, China. The study assessed the current MSW management system, as well as a set of alternative scenarios, to investigate trade-offs between economy and GHG emissions mitigation. Additionally, contribution analysis was conducted on both LCA and LCC to identify key issues driving environmental and economic impacts. The results show that the current Tianjin’s MSW management system emits the highest GHG and costs the least, whereas the situation reverses in the integrated scenario. The key issues identified by the contribution analysis show no linear relationship between the global warming impact and the cost impact in MSW management system. The landfill gas utilization scenario is indicated as a potential optimum scenario by the proposed E/E analysis, given the characteristics of MSW, technology levels, and chosen methodologies. The E/E analysis provides an attractive direction towards sustainable waste management, though some questions with respect to uncertainty need to be discussed further.     

Multi-objective optimization of solid waste flows: environmentally sustainable strategies for municipalities

An approach to sustainable municipal solid waste (MSW) management is presented, with the aim of supporting the decision on the optimal flows of solid waste sent to landfill, recycling and different types of treatment plants, whose sizes are also decision variables. This problem is modeled with a non-linear, multi-objective formulation. Specifically, four objectives to be minimized have been taken into account, which are related to economic costs, unrecycled waste, sanitary landfill disposal and environmental impact (incinerator emissions). An interactive reference point procedure has been developed to support decision making; these methods are considered appropriate for multi-objective decision problems in environmental applications. In addition, interactive methods are generally preferred by decision makers as they can be directly involved in the various steps of the decision process. Some results deriving from the application of the proposed procedure are presented. The application of the procedure is exemplified by considering the interaction with two different decision makers who are assumed to be in charge of planning the MSW system in the municipality of Genova (Italy).     

A multi-objective approach to solid waste management

The issue addressed in this paper consists in the localization and dimensioning of transfer stations, which constitute a necessary intermediate level in the logistic chain of the solid waste stream, from municipalities to the incinerator. Contextually, the determination of the number and type of vehicles involved is carried out in an integrated optimization approach. The model considers both initial investment and operative costs related to transportation and transfer stations. Two conflicting objectives are evaluated, the minimization of total cost and the minimization of environmental impact, measured by pollution. The design of the integrated waste management system is hence approached in a multi-objective optimization framework. To determine the best means of compromise, goal programming, weighted sum and fuzzy multi-objective techniques have been employed. The proposed analysis highlights how different attitudes of the decision maker towards the logic and structure of the problem result in the employment of different methodologies and the obtaining of different results. The novel aspect of the paper lies in the proposal of an effective decision support system for operative waste management, rather than a further contribution to the transportation problem. The model was applied to the waste management of optimal territorial ambit (OTA) of Palermo (Italy).     

Development of a purpose built landfill system for the control of methane emissions from municipal solid waste

In the present paper, a new system of purpose built landfill (PBLF) has been proposed for the control of methane emissions from municipal solid waste (MSW), by considering all favourable conditions for improved methane generation in tropical climates. Based on certain theoretical considerations multivariate functional models (MFMs) are developed to estimate methane mitigation and energy generating potential of the proposed system. Comparison was made between the existing waste management system and proposed PBLF system. It has been found that the proposed methodology not only controlled methane emissions to the atmosphere but also could yield considerable energy in terms of landfill gas (LFG). Economic feasibility of the proposed system has been tested by comparing unit cost of waste disposal in conventional as well as PBLF systems. In a case study of MSW management in Mumbai (INDIA), it was found that the unit cost of waste disposal with PBLF system is seven times lesser than that of the conventional waste management system. The proposed system showed promising energy generation potential with production of methane worth of Rs. 244 millions/y ($5.2 million/y). Thus, the new waste management methodology could give an adaptable solution for the conflict between development, environmental degradation and natural resources depletion.     

Proposal for the integration of decentralised composting of the organic fraction of municipal solid waste into the waste management system of Cuba

Municipal solid waste (MSW) generation and management in Cuba was studied with a view to integrating composting of the organic fractions of MSW into the system. Composting is already included as part of the environmental strategy of the country as an appropriate waste management solution. However, no programme for area-wide implementation yet exists. The evaluation of studies carried out by some Cuban and international organisations showed that organic matter comprises approximately 60-70% of the MSW, with households being the main source. If all organic waste fractions were considered, the theoretical amount of organic waste produced would be approximately 1 Mio. Mg/a, leading to the production of approximately 0.5 Mio. Mg/a of compost. Composting could, therefore, be a suitable solution for treating the organic waste fractions of the MSW. Composting would best be carried out in decentralised systems, since transportation is a problem in Cuba. Furthermore, low technology and low budget composting options should be considered due to the problematic local economic situation. The location for such decentralised composting units would optimally be located at urban agricultural farms, which can be found all over Cuba. These farms are a unique model for sustainable farming in the world, and have a high demand for organic fertiliser. In this paper, options for the collection and impurity-separation in urban areas are discussed, and a stepwise introduction of source-separation, starting with hotel and restaurant waste, is suggested. For rural areas, the implementation of home composting is recommended.     

Research on solid waste management system: to improve existing situation in Corlu Town of Turkey

Over the past decades, uncontrolled population growth and rapid urbanization and industrialization have resulted in environmental problems in Corlu Town, Turkey. One of the most important problems is solid waste due to inadequate management practices. Nowadays, increasing public awareness of the environment compels local authorities to define and to adopt new solutions for waste management. This paper presents a general overview of current solid waste management practices in Corlu Town and principles of the recommended municipal solid waste (MSW) management system. In Corlu, 170 tonnes of municipal solid waste are generated each day, or 1.150 kg per capita per day. Approximately one-half of the municipal solid waste generated is organic material and 30% of the MSW consists of recyclable materials. The recommended system deals with maximizing recycling and minimizing landfilling of municipal solid waste, and consists of separation at source, collection, sorting, recycling, composting and sanitary landfilling. This study also analyzed the recommended system with respect to feasibility and economics. To evaluate whether the suggested system is cost effective or not, the operating cost of the recommended system and market prices of recyclable materials were compared, and the results show that the recommended system will reduce required landfill volume up to 27% of compared to the present situation. The profit of the recommended system is estimated to be about 80 million US dollars.     

Comparison of old and new municipal solid waste management systems in Denizli, Turkey

Rapid economic growth, increasing population and change in living standards contribute to increasing the generation rate of municipal solid waste (MSW) in Denizli city, like other Turkish cities. The improper and poor MSW management system (old system) in Denizli caused environmental problems originating from the uncontrolled release of methane and leachate. In addition, the disposal of recyclable materials in unsanitary landfills is responsible for the consumption and destruction of natural sources. This paper presents a general overview of old and new MSW management practices in Denizli. Detailed data on MSW management practices including collection, transportation, disposal and recycling have been presented. The amount of solid waste generated in Denizli over the last decade has increased steadily over the years, from 108,500 tons in 1995 to 179,495 tons in 2006. The average MSW generation rate was found to be 1.23kg/day per capita. The major constituent of MSW in Denizli is food waste, but the percentage of recyclable waste has increased significantly recently. Except for metal wastes, the percentages of recyclable waste materials in Denizli are higher than in all neighborhood cities. The objective of this study is to compare the old and new MSW management systems in Denizli city. The MSW management system has been changed entirely last five years. A dumpsite was closed and a sanitary landfill with a composting facility was constructed. In addition, source separated collection has been carried out since 2002. The quantity of recyclable waste collected increased from 195 to 1549 tons. The amount of recyclable waste will continue to be increased by expanding the source separation collection system to all the districts of the city and preventing scavenging. Thus, revenue from recyclable waste ($7227 in 2006) is expected to increase. In addition, the capacity of the composting facility will be increased. Most importantly, information to increase public participation and awareness in municipal recovery programs has to be provided.     

Life-cycle assessment of municipal solid waste management alternatives with consideration of uncertainty: SIWMS development and application

This paper describes the development and application of the Stochastic Integrated Waste Management Simulator (SIWMS) model. SIWMS provides a detailed view of the environmental impacts and associated costs of municipal solid waste (MSW) management alternatives under conditions of uncertainty. The model follows a life-cycle inventory approach extended with compensatory systems to provide more equitable bases for comparing different alternatives. Economic performance is measured by the net present value. The model is verified against four publicly available models under deterministic conditions and then used to study the impact of uncertainty on Sydney’s MSW management ‘best practices’. Uncertainty has a significant effect on all impact categories. The greatest effect is observed in the global warming category where a reversal of impact direction is predicted. The reliability of the system is most sensitive to uncertainties in the waste processing and disposal. The results highlight the importance of incorporating uncertainty at all stages to better understand the behaviour of the MSW system.     

An environmentally sustainable decision model for urban solid waste management

The aim of this work is to present the structure and the application of a decision support system (DSS) designed to help decision makers of a municipality in the development of incineration, disposal, treatment and recycling integrated programs. Specifically, within a MSW management system, several treatment plants and facilities can generally be found: separators, plants for production of refuse derived fuel (RDF), incinerators with energy recovery, plants for treatment of organic material, and sanitary landfills. The main goal of the DSS is to plan the MSW management, defining the refuse flows that have to be sent to recycling or to different treatment or disposal plants, and suggesting the optimal number, the kinds, and the localization of the plants that have to be active. The DSS is based on a decision model that requires the solution of a constrained non-linear optimization problem, where some decision variables are binary and other ones are continuous. The objective function takes into account all possible economic costs, whereas constraints arise from technical, normative, and environmental issues. Specifically, pollution and impacts, induced by the overall solid waste management system, are considered through the formalization of constraints on incineration emissions and on negative effects produced by disposal or other particular treatments.     

SLFP: a stochastic linear fractional programming approach for sustainable waste management

A stochastic linear fractional programming (SLFP) approach is developed for supporting sustainable municipal solid waste management under uncertainty. The SLFP method can solve ratio optimization problems associated with random information, where chance-constrained programming is integrated into a linear fractional programming framework. It has advantages in: (1) comparing objectives of two aspects, (2) reflecting system efficiency, (3) dealing with uncertainty expressed as probability distributions, and (4) providing optimal-ratio solutions under different system-reliability conditions. The method is applied to a case study of waste flow allocation within a municipal solid waste (MSW) management system. The obtained solutions are useful for identifying sustainable MSW management schemes with maximized system efficiency under various constraint-violation risks. The results indicate that SLFP can support in-depth analysis of the interrelationships among system efficiency, system cost and system-failure risk.     

A hybrid procedure for MSW generation forecasting at multiple time scales in Xiamen City,China

Accurate forecasting of municipal solid waste (MSW) generation is crucial and fundamental for the planning, operation and optimization of any MSW management system. Comprehensive information on waste generation for month-scale, medium-term and long-term time scales is especially needed, considering the necessity of MSW management upgrade facing many developing countries. Several existing models are available but of little use in forecasting MSW generation at multiple time scales. The goal of this study is to propose a hybrid model that combines the seasonal autoregressive integrated moving average (SARIMA) model and grey system theory to forecast MSW generation at multiple time scales without needing to consider other variables such as demographics and socioeconomic factors. To demonstrate its applicability, a case study of Xiamen City, China was performed. Results show that the model is robust enough to fit and forecast seasonal and annual dynamics of MSW generation at month-scale, medium- and long-term time scales with the desired accuracy. In the month-scale, MSW generation in Xiamen City will peak at 132.2 thousand tonnes in July 2015 – 1.5 times the volume in July 2010. In the medium term, annual MSW generation will increase to 1518.1 thousand tonnes by 2015 at an average growth rate of 10%. In the long term, a large volume of MSW will be output annually and will increase to 2486.3 thousand tonnes by 2020 – 2.5 times the value for 2010. The hybrid model proposed in this paper can enable decision makers to develop integrated policies and measures for waste management over the long term.     

Logistical management and private sector involvement in reducing the cost of municipal solid waste collection service in the Tubas area of the West Bank

This paper addresses the problems of the municipal solid waste (MSW) collection system in the Tubas district of Palestine. More specifically, it addresses the often-voiced concerns pertaining to low efficiency as well as environmental problems. This was carried out through a systematic methodological approach. The paper illustrates how a private company applied a logistical management strategy, by rescheduling the MSW collection system, reallocating street solid waste containers and minimizing vehicle routing. The way in which the MSW collection timetable was rescheduled decreased the operating expenses and thus reduced MSW collection costs. All data needed to reschedule the collection timetable and optimize vehicle routing were based on actual field measurements. The new MSW collection timetable introduced by a private company was monitored for a period of a month. The new system resulted in an improvement in the MSW collection system by reducing the collection cost to a level that is socially acceptable (US dollars 3.75/family/month), as well as economically and environmentally sound.     

The current situation of solid waste management in China

With economic development, the quantity of solid waste is increasing rapidly in China; the total quantities of municipal solid waste (MSW), industrial solid waste (ISW), and hazardous waste (HW) in 2002 were 136.5 million tons, 945 million tons, and 10 million tons, respectively. In 2002, the quantity of MSW disposed of was 74.04 million tons, 89.30% of which was landfilled, 3.72% was incinerated, and 6.98% was composted. There are currently 651 disposal facilities for MSW in China. Mining gangue is the largest component of ISW, making up 27.5% of the total. In the Chinese industrial sector, the coal mining and processing industry contributed most to the total quantity of ISW, with 16.0% of the total quantity of ISW generated by this sector. In total, 44% of HW was recycled, 27% was stored, 13.5% was disposed of, and 15.4% was discharged. Of the total HW generated, 40% was produced by the chemical materials and chemical products industry. Five categories of HW, i.e., waste alkali, waste acid, inorganic fluoride waste, copper waste, and inorganic cyanide waste, made up 57.8% of the total HW generated. Solid waste pollution has become a huge challenge faced by those involved in Chinese environmental management, but this can be seen as an opportunity to improve environmental quality. This article introduces the strategies taken to improve solid waste management in China.     

Examining the effectiveness of municipal solid waste management systems: an integrated cost-benefit analysis perspective with a financial cost modeling in Taiwan

In order to develop a sound material-cycle society, cost-effective municipal solid waste (MSW) management systems are required for the municipalities in the context of the integrated accounting system for MSW management. Firstly, this paper attempts to establish an integrated cost-benefit analysis (CBA) framework for evaluating the effectiveness of MSW management systems. In this paper, detailed cost/benefit items due to waste problems are particularly clarified. The stakeholders of MSW management systems, including the decision-makers of the municipalities and the citizens, are expected to reconsider the waste problems in depth and thus take wise actions with the aid of the proposed CBA framework. Secondly, focusing on the financial cost, this study develops a generalized methodology to evaluate the financial cost-effectiveness of MSW management systems, simultaneously considering the treatment technological levels and policy effects. The impacts of the influencing factors on the annual total and average financial MSW operation and maintenance (O&M) costs are analyzed in the Taiwanese case study with a demonstrative short-term future projection of the financial costs under scenario analysis. The established methodology would contribute to the evaluation of the current policy measures and to the modification of the policy design for the municipalities.     

An interval-parameter stochastic robust optimization model for supporting municipal solid waste management under uncertainty

A stochastic robust interval linear programming model (IPRO) was developed for supporting municipal solid waste management under uncertainty. The model improves upon the existing stochastic robust optimization (SRO) and interval linear programming (ILP) methods by allowing evaluations of trade-offs among expected costs, cost variability, and risk of violating relax constraints simultaneously, as well as reflections of complex uncertainties through both interval and stochastic theories. A long-term waste management problem was used to demonstrate the applicability of IPRO model. The results indicated that IPRO normally led to interval solutions, where waste-management alternatives could be generated by adjusting the decision-variable values within their intervals. The model could also help waste managers to identify desired policies that under various environmental, economic, system-feasibility and system-reliability constraints.     

Conceptual modeling to optimize the haul and transfer of municipal solid waste

Two conceptual mixed integer linear optimization models were developed to optimize the haul and transfer of municipal solid waste (MSW) prior to landfilling. One model is based on minimizing time (h/d), whilst the second model is based on minimizing total cost (euro/d). Both models aim to calculate the optimum pathway to haul MSW from source nodes (waste production nodes, such as urban centers or municipalities) to sink nodes (landfills) via intermediate nodes (waste transfer stations). The models are applicable provided that the locations of the source, intermediate and sink nodes are fixed. The basic input data are distances among nodes, average vehicle speeds, haul cost coefficients (in euro/ton km), equipment and facilities' operating and investment cost, labor cost and tipping fees. The time based optimization model is easier to develop, since it is based on readily available data (distances among nodes). It can be used in cases in which no transfer stations are included in the system. The cost optimization model is more reliable compared to the time model provided that accurate cost data are available. The cost optimization model can be a useful tool to optimally allocate waste transfer stations in a region and can aid a community to investigate the threshold distance to a landfill above which the construction of a transfer station becomes financially beneficial. A sensitivity analysis reveals that queue times at the landfill or at the waste transfer station are key input variables. In addition, the waste transfer station ownership and the initial cost data affect the optimum path. A case study at the Municipality of Athens is used to illustrate the presented models.     

Municipal solid waste management challenges in developing countries--Kenyan case study

This paper provides an overview of the state of municipal solid waste management (MSWM) by local authorities in Kenya as a case study of a low-income developing country. Approaches of possible solutions that can be undertaken to improve municipal solid waste (MSW) services are discussed. Poor economic growth (1.1% in 1993) has resulted in an increase in the poverty level which presently stands at 56%. Migration from the rural areas to the urban areas has resulted in unplanned settlements in suburban areas accommodating about 60% of the urban population on only 5% urban land area. Political interference also hampers smooth running of local authorities. Vulnerability of pollution of surface and groundwater is high because local authorities rarely considered environmental impact in siting MSW disposal sites. Illegal dumping of MSW on the river banks or on the roadside poses environmental and economic threats on nearby properties. Poor servicing of MSW collection vehicles, poor state of infrastructure and the lack of adequate funding militate against optimization of MSW disposal service. The rural economy needs to be improved if rural-urban migration is to be managed. Involvement of stakeholders is important to achieve any meaningful and sustainable MSWM. The role of the informal sector through community-based organizations (CBOs), Non-Governmental Organizations (NGOs) and the private sector in offering solutions towards improvement of MSWM also is explored.     

Municipal solid waste management in Lahore City District,Pakistan

This study deals with generation, composition, collection, transportation, and disposal, as well as the present cost of the waste management on the basis of 60% collection of the total waste and the cost of proposed improved system of management on the basis of 100% waste collection using the IWM-2 LCI model. A GIS map of Data Ganj Bakhsh Town (DGBT) of Lahore City District showing communal storage facilities is also provided. DGBT has a population of 1,624,169 living in 232,024 dwellings. The total waste generated per year is 500,000 tons, or 0.84/kg/cap/day. Presently 60% of the MSW is collected and disposed in open dumps, while 40% is not collected and lies along roadsides, streets railway lines, depressions, vacant plots, drains, storm drains and open sewers. In DGBT, 129 containers of 5-m³ capacity, 120 containers of 10-m³ capacity and 380 skips of 2.5-m³ capacity are placed for waste collection. The overall collection and disposal cost of the MSW of DGBT is $3,177,900/yr, which is $10.29/ton. Modeling was conducted using the IWM-2 model for improved collection and disposal on the basis of 100% service, compared to the current 60% service. The modelled cost is $8.3/per ton, which is 20% less than the present cost, but the overall cost of 100% collection and disposal increases to $4,155,737/yr.     

A multi-objective programming model for assessment the GHG emissions in MSW management

In this study a multi-objective mathematical programming model is developed for taking into account GHG emissions for Municipal Solid Waste (MSW) management. Mathematical programming models are often used for structure, design and operational optimization of various systems (energy, supply chain, processes, etc.). The last twenty years they are used all the more often in Municipal Solid Waste (MSW) management in order to provide optimal solutions with the cost objective being the usual driver of the optimization. In our work we consider the GHG emissions as an additional criterion, aiming at a multi-objective approach. The Pareto front (Cost vs. GHG emissions) of the system is generated using an appropriate multi-objective method. This information is essential to the decision maker because he can explore the trade-offs in the Pareto curve and select his most preferred among the Pareto optimal solutions. In the present work a detailed multi-objective, multi-period mathematical programming model is developed in order to describe the waste management problem. Apart from the bi-objective approach, the major innovations of the model are (1) the detailed modeling considering 34 materials and 42 technologies, (2) the detailed calculation of the energy content of the various streams based on the detailed material balances, and (3) the incorporation of the IPCC guidelines for the CH₄ generated in the landfills (first order decay model). The equations of the model are described in full detail. Finally, the whole approach is illustrated with a case study referring to the application of the model in a Greek region.