The application of a vehicle routing model to a waste-collection problem: two case studies

In this paper we suggest a unique model for estimating the operating cost of each of three waste-collection systems. Under the traditional system, which is widely used, waste is typically collected in plastic bags and a three-man crew is needed on each vehicle. The other two systems require a one-man crew for vehicle collecting street containers. The side-loader system with fixed body automatically empties street containers into the vehicle body and empties the load at the disposal site. The side-loader system with demountable body allows the separation of the waste collection phase from transport to the disposal site, since the vehicle body can be demounted. We also present two case studies and show how the estimation of operating costs is a critical issue in decisions regarding the type of system to be used for waste collection.     

A multi-methodological approach to the development of a regional solid waste management system

The management of solid waste at regional level has received considerable attention over the last years. Increased consumption levels are causing an exacerbation of the problem, whereas the sensitivity of the public over environmental issues makes its solution harder. Although the main difficulties in resolving the different occurrences of the problem belong to the realm of policy making, so far the employment of operational research and systems methods seems to adopt a purely technocratic stance, concentrating on the content and understating the solution process. In the different formulations of the problem as static optimization relating to the economics of the location of the treatment facilities and the methods and routes of waste transportation, the dynamics of the issue and the intervention activities are neglected, whereas cognitive and social perspectives of the solution process are objectified and over-rationalized. This paper aims at demonstrating how the solid waste management (SWM) problem and its solution process can be addressed in a more holistic way by adopting a multi-methodological point of view. Towards this end, we present the combined application of soft systems methodology, system dynamics and multi-objective optimization in an action research project for the development of an SWM system for a specific region in Greece.     

Modelling and optimisation of electricity,steam and district heating production for a local Swedish utility

District heating may help reduce environmental impact and energy costs, but policy instruments and waste management may influence operations. The energy system optimisation model MODEST has been used for 50 towns, regions and a nation. Investments and operation that satisfy energy demand at minimum cost are found through linear programming. This paper describes the application of MODEST to a municipal utility, which uses several fuels and cogeneration plants. The model reflects diurnal and monthly demand fluctuations.Several studies of the Linköping utility are reviewed. These indicate that the marginal heat cost is lower in summer; a new waste or wood fired cogeneration plant is more profitable than a natural-gas-fired combined cycle; material recycling of paper and hard plastics is preferable to waste incineration from an energy-efficiency viewpoint; and considering external costs enhances wood fuel use. Here, an emission limit is used to show how fossil-fuel cogeneration displaces CO₂ from coal-condensing plants.     

A fuzzy-robust stochastic multiobjective programming approach for petroleum waste management planning

This paper proposes a fuzzy-robust stochastic multiobjective programming (FRSMOP) approach, which integrates fuzzy-robust linear programming and stochastic linear programming into a general multiobjective programming framework. A chosen number of noninferior solutions can be generated for reflecting the decision-makers’ preferences and subjectivity. The FRSMOP method can effectively deal with the uncertainties in the parameters expressed as fuzzy membership functions and probability distribution. The robustness of the optimization processes and solutions can be significantly enhanced through dimensional enlargement of the fuzzy constraints. The developed FRSMOP was then applied to a case study of planning petroleum waste-flow-allocation options and managing the related activities in an integrated petroleum waste management system under uncertainty. Two objectives are considered: minimization of system cost and minimization of waste flows directly to landfill. Lower waste flows directly to landfill would lead to higher system costs due to high transportation and operational costs for recycling and incinerating facilities, while higher waste flows directly to landfill corresponding to lower system costs could not meet waste diversion objective environmentally. The results indicate that uncertainties and complexities can be effectively reflected, and useful information can be generated for providing decision support.     

WASAN: The development of a facilitated methodology for structuring a waste minimisation problem

This paper contributes a new methodology called Waste And Source-matter ANalyses (WASAN) which supports a group in building agreeable actions for safely minimising avoidable waste. WASAN integrates influences from the Operational Research (OR) methodologies/philosophies of Problem Structuring Methods, Systems Thinking, simulation modelling and sensitivity analysis as well as industry approaches of Waste Management Hierarchy, Hazard Operability (HAZOP) Studies and As Low As Reasonably Practicable (ALARP). The paper shows how these influences are compiled into facilitative structures that support managers in developing recommendations on how to reduce avoidable waste production. WASAN is being designed as Health and Safety Executive Guidance on what constitutes good decision making practice for the companies that manage nuclear sites. In this paper we report and reflect on its use in two soft OR/problem structuring workshops conducted on radioactive waste in the nuclear industry.     

A decision support system for urban waste management

This paper describes a decision support system, for urban waste management in a regional area, to be used for evaluating general policies for service organisation of the collection and for identifying areas suitable for locating waste treatment and disposal plants. The Decision Support System (DSS) is applied to a selected provinces in Sicily. The decision support system allows the generation and evaluation of suitable alternatives with respect to salient features of the problem, especially environmental consequences. The paper describes the identification and collection of relevant information, the structuring of a database, the design of combinatorial optimisation algorithms for solving the core location problem, the study of models for evaluating the different alternatives and their framing in a complete multicriteria decision model. Finally, the solution of the case study, by means of the DSS, is described.     

Radial basis neural tree model for improving waste recovery process in a paper industry

In this article, we propose a novel hybridization of regression trees (RTs) and radial basis function networks, namely, radial basis neural tree model, for waste recovery process (WRP) improvement in a paper industry. As a by‐product of the paper manufacturing process, a lot of waste along with valuable fibers and fillers come out from the paper machine. The WRP involves separating the unwanted materials from the valuable ones so that the recovered fibers and fillers can be further reused in the production process. This job is done by fiber‐filler recovery equipment (FFRE). The efficiency of FFRE depends on several crucial process parameters, and monitoring them is a difficult proposition. The proposed model can be useful to find the essential parameters from the set of available data and to perform prediction task to improve WRP efficiency. An idea of parameter optimization along with regularity conditions for the universal consistency of the proposed model is given. The proposed model has the advantages of easy interpretability and excellent performance when applied to the FFRE efficiency improvement problem. Improved waste recovery will help the industry to become environmentally friendly with less ecological damage apart from being cost‐effective.     

Time of complete displacement of an immiscible compressible fluid by water in porous media: Application to gas migration in a deep nuclear waste repository

A system of evolutionary partial differential equations (PDEs) describing the two-phase flow of immiscible fluids, such as water–gas, through porous media is studied. In this formulation, the wetting and nonwetting phases are treated to be incompressible and compressible, respectively. This treatment is indeed necessary when a compressible nonwetting phase is subjected to compression during confinement. The system of PDEs consists of an evolution equation for the wetting-phase saturation and an evolution equation for the pressure in the nonwetting phase. This system is applied to the problem of unsaturated flows to assess gas migration and two-phase flow through engineered and geological barriers for a deep repository for radioactive waste. This paper is primarily concerned with the large time behavior of solutions of this system. Under some realistic assumptions on the data, we derive estimates of the speed of propagation of the gas by water in porous media. Namely, we establish estimates of time stabilization for the water saturation to a constant limit profile. The analysis is based on the energy methods whose main idea involves deriving and studying suitable ordinary differential inequalities. We show that the time of complete displacement of a gas by water may be at most infinite or finite depending essentially on the power parameters defining the capillary pressure and the relative permeabilities. This result is then illustrated with two examples in the context of gas migration in a deep nuclear waste repository. We consider Van Genuchten’s and Brooks–Corey’s models for a two-phase water–gas system.     

A Planning Model for the Development of Waste Material Recycling Programmes

Material recycling is quickly becoming the most visible component of municipal solid waste management systems, and optimization models could play a prominent role in the long-term cost-effective planning of these systems. In this paper, we develop a mixed integer programming model for the recycling of various by-product materials within the overall waste system. This model is solvable on a microcomputer for reasonable problem dimensions, and the planning methodology is applied to a hypothetical municipality to illustrate the potential utility of the developed modelling approach.     

Designing an optimal resource recovery facility

With the ever expanding consuming societies all over the world, communities are producing increasing amounts of solid waste. A proper disposal of the waste has always been considered a matter of public interest and a basic service to the residents. Since this service requires a vast amount of economic resources and land sites, which are becoming scarce, many communities, particularly in the United States. are facing a difficult problem of how to continue to provide a cost-effective solid waste disposal service to their residents.A search for suitable land for siting a landfill is both difficult and costly. Further, the sensitivity in recent years to the quality of environment has measurably heightened the cost of developing and operating a landfill site. Consequently, more and more communities have been studying alternative disposal programs to alleviate the problem. One such system, which has recently come into focus, is the resource recovery alternative. The combustion of solid waste in specially designed incinerators and simultaneous recovery of the heat energy are the underlying principles this system is built on.This paper suggests a model for optimizing the size and configuration of resource recovery facility to suit the present and anticipated disposal needs of a community. The model discussed requires a minimal computational effort.     

带有加压泵站的污水管网系统的优化计算

本对带有加压泵站污水管网系统的优化问题进行了研究，建立了优化计算的数学模型，根据模型提出了有效的优化方法编制了相应程序，最后通过实际案例计算，比较表明，效果令人满意。     

Optimal batch sizing in a multi-stage production system with rework consideration

In a production system, rework process plays an important role in eliminating waste and effectively controlling the cost of manufacturing. Determining the optimal batch size in a system that allows for rework is, therefore, a worthwhile objective to minimize the inventory cost of work-in-processes and the finished goods. In this paper, models for the optimum batch quantity in a multi-stage system with rework process have been developed for two different operational policies. Policy 1 deals with the rework within the same cycle with no shortage and policy 2 deals with the rework done after N cycles, incurring shortages in each cycle. The major components that play a role in minimizing this cost of the system are manufacturing setups, work-in-processes, storage of finished goods, rework processing, waiting-time, and penalty costs to discourage the generation of defectives. The mathematical structure of this rework processing model falls under a nonlinear convex programming problems for which a closed-form solution has been proposed and results are demonstrated through numerical examples, followed by sensitivity analyses of different important parameters. It is concluded that the total cost in policy 2 tends to be smaller than that in policy 1 at lower proportion of defectives if the in-process carrying cost is low. Policy 2 may be preferred when the work-in-process carrying cost is low and the penalty cost is negligible.     

Environmental site evaluation of waste management facilities embedded into EUGÈNE model: A multicriteria approach

EUGÈNE is a sophisticated mixed integer linear programming model developed to help regional decision makers on long-term planning for solid waste management activities. The model removes almost every limitations encountered in other waste management models and contains a large quantity of variables and constraints. The method used to embed waste management environmental parameters in the EUGÈNE model consists in building global impact index (GII) for all site/facility combinations. First, an environmental and spatial evaluation of waste management facilities over sites is based on qualitative and quantitative criteria measuring biophysical and social impacts. Spatial analysis is carried out by geographical information system routines. Then, a multicriteria analysis ranks all site/facility combinations, according to their global performance based on all criteria. The net flow, computed by the PROMETHEE multicriteria outranking method, is considered as a GII to be embedded into EUGÈNE. The model objective function is thus modified to minimize total system cost and GII. Some practical results obtained for the City of Montreal are discussed.     

The existence of solutions to a corrosion model

In this work, we consider a corrosion model of iron based alloy in a nuclear waste repository. It consists of a PDE system, similar to the steady-state drift–diffusion system arising in semiconductor modelling. The main difference lies in the boundary conditions, since they are Robin boundary conditions and imply an additional coupling between the equations. Using a priori estimates for the solution and Schauder’s fixed point theorem, we show the existence of solutions to the corrosion model.     

The EOQ repair and waste disposal model with variable setup numbers

In a previous paper the author discussed an EOQ model in which the stationary demand can be satisfied by newly made products and by repaired used products. In the modelled situation some share of the used products is collected and later repaired; the other products are disposed outside according to some waste disposal rate. In the present paper this model is extended to the case of variable setup numbers n and m for production and repair within some collection time interval. First, for a fixed waste disposal rate the cost optimal setup numbers and the minimum cost are determined. Secondly, the minimum cost is analysed as a function of this rate and it is shown to be convex for small and medium waste disposal rates and to be concave for large rates. Thirdly, the existence and generation of cost optimal waste disposal rates are discussed.     

Official recycling and scavengers: Symbiotic or conflicting?

Nowadays, especially in developed countries, the traditional collection of end-of-use products by scavengers has been displaced by formal waste recovery systems. However, scavenging still exists, especially in places with collection capacity shortages and/or low living standards. Besides its obvious social implications, the financial and environmental aspects of scavenging are certainly not trivial. Informal recycling of waste electrical and electronic equipment (WEEE) by scavengers not only constrains profits of the formal system. In their effort to recover the value of end-of-use products, scavengers also pollute the environment if toxic substances leak when WEEE is not properly disposed of. We investigate the impact of scavenging on the operations of the formal recovery system of WEEE, under three regulatory measures, using system dynamics methodology. By using data from a real world closed-loop supply chain that operates in Greece extended numerical experimentation revealed that a legislation incorporating scavengers into the formal waste recovery system (instead of either ignoring or prohibiting their participation) is beneficial for economical, environmental and social sustainability.     

Optimal selection of a landfill disposal site using a modified fuzzy utility approach

The present paper develops an integrated fuzzy based model to select an optimal landfill site among the given alternative sites by using the concept of fuzzyutility method and multi-nomial logit theory. The suitability of different landfill sites are evaluated based on some important criteria involved in the process such as accessibility and transportation; environmental, geological and climatic conditions; socioeconomic conditions; land use pattern; and safety at the selected site. These criteria are assessed qualitatively by the decision makers based on their relative degree of importance. The importance weights and ratings of each criterion have been defined in the form of triplets of triangular fuzzy numbers by taking opinion of the decision makers. The corresponding triplets of ratings of each site are used to derive the utility value of the alternative sites. A multi-nomial logit model has been applied to calculate the probability of selection of each alternative site which can help policy makers to take appropriate decisions. Finally, the proposed methodology has been applied to allocate suitable landfill sites for disposing off municipal solid waste for Pilani town which is located in Jhunjhunu district of Rajasthan. The results evaluated by the modified fuzzy utility are also compared to the outputs of a direct method which is basically based on certain linguistic aggregation operators for group decision making. Computational results clearly demonstrate that the results obtained by the proposed method are coinciding very well and prepares a basis to adopt an overall strategy for selecting appropriate landfill site for proper solid waste disposal and its management.     

Fuzzy理论在工程环境灾害预测中的应用

针对矿山大型排土场所出现的滑坡等工程环境灾害的预测与防治问题,着重探讨排土场边坡失稳破坏预测问题.文中采用Fuzzy数学中的Fuzzy概率测度理论建立理论预测分析模型,并对大型排土场边坡失稳破坏的Fuzzy概率测度进行具体的预测分析,所获结果与已有的经典分析方法所获理论结果一致.针对矿山大型排土场所出现的滑坡等工程环境灾害防治问题,提出了具体的防治技术措施.     

A web-based decision support system for waste lube oils collection and recycling

This paper presents a web-based decision support system (DSS) that enables schedulers to tackle reverse supply chain management problems interactively. The focus is on the efficient and effective management of waste lube oils collection and recycling operations. The emphasis is given on the systemic dimensions and modular architecture of the proposed DSS. The latter incorporates intra- and inter-city vehicle routing with real-life operational constraints using shortest path and sophisticated hybrid metaheuristic algorithms. It is also integrated with an Enterprise Resource Planning system allowing the utilization of particular functional modules and the combination with other peripheral planning tools. Furthermore, the proposed DSS provides a framework for on-line monitoring and reporting to all stages of the waste collection processes. The system is developed using a web architecture that enables sharing of information and algorithms among multiple sites, along with wireless telecommunication facilities. The application to an industrial environment showed improved productivity and competitiveness, indicating its applicability on realistic reverse logistical planning problems.     

Comparison of discrete- and continuous-time models for scheduling waste wood processing facilities

With the growing significance of environmental awareness, the role of renewable materials and their reuse and recycling possibilities have become increasingly important. Wood is one of the best examples for this, as it is a material that has a variety of primary uses, while also being a prime candidate for reuse and recycling. An important phase in most waste wood value chains is the processing of bulk waste from various sources, usually by means of shredding. This paper presents methods for scheduling the machines in such a waste wood processing facility, where incoming deliveries of different types of wood are processed by a series of treatment and transformation steps to produce shredded wood. Two mathematical models are developed for the problem that both allow overlaps between consecutive steps to optimize resource flow through the system. One of these is a more traditional discrete-time model, while the other is precedence-based and uses continuous-time variables for the timing of the various tasks. Both modeling techniques have their advantages and shortcomings with regard to the ease of integration of further problem-specific parameters and requirements. Next to providing a sound approach for the identified problem class, another aim is to evaluate, which technique suits better for this problem class, and should be used as a basis for extended and integrated cases in the future. Thus, the performance of these models is compared on instances that were randomly generated based on real-world distributions from the literature.