A novel sustainable decision making model for municipal solid waste management

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Abstract

This paper reviews several models developed to support decision making in municipal solid waste management (MSWM). The concepts underlying sustainable MSWM models can be divided into two categories: one incorporates social factors into decision making methods, and the other includes public participation in the decision-making process. The public is only apprised or takes part in discussion, and has little effect on decision making in most research efforts. Few studies have considered public participation in the decision-making process, and the methods have sought to strike a compromise between concerned criteria, not between stakeholders. However, the source of the conflict arises from the stakeholders’ complex web of value. Such conflict affects the feasibility of implementing any decision. The purpose of this study is to develop a sustainable decision making model for MSWM to overcome these shortcomings. The proposed model combines multicriteria decision making (MCDM) and a consensus analysis model (CAM). The CAM is built up to aid in decision-making when MCDM methods are utilized and, subsequently, a novel sustainable decision making model for MSWM is developed. The main feature of CAM is the assessment of the degree of consensus between stakeholders for particular alternatives. A case study for food waste management in Taiwan is presented to demonstrate the practicality of this model.

Introduction

Several models have been developed in recent decades to support decision making in municipal solid waste management (MSWM). In the 1970s, the goals of the MSWM model were simple and narrow, such as optimizing waste collection routes for vehicles (Truitt et al., 1969) or locating appropriate transfer stations (Esmaili, 1972, Helms and Clark, 1974). In the 1980s, the focus was extended to encompass MSWM on a system level, minimizing MSWM cost (Hasit and Warner, 1981, Jenkins, 1982, Perlack and Willis, 1985). In the 1990s, the factors considered in MSWM models were principally economic (e.g., system cost and system benefit), environmental (air emission, water pollution) and technological (the maturity of technology). Two decision-making models, multiobjective programming (MOP) and multicriteria decision making (MCDM), as well as an environmental impact assessment model, the life cycle assessment (LCA), were often used to aid the decision-making in MSWM. Numerous studies applied LCA to evaluate the environmental impact of MSWM alternatives. (Barton et al., 1996, Powell et al., 1996, Finnveden, 1999, Powell, 2000). Some of these methods were further developed for simulation modeling, such as ORWARE (Dalemo et al., 1997, Sonesson et al., 1997, Eriksson et al., 2002) and EUGENE (Berger et al., 1999). Multiobjective programming is a popular method utilized to solve MSWM problems, such as locating sites, and choosing alternatives or strategies (Alidi, 1996, Chang and Hwang, 1996, Chang and Wang, 1996, Chang and Wei, 1999). MCDM is also a commonly used method to resolve MSWM problems. The characteristic of MCDM is that it facilitates choosing the best alternative among several alternatives by assessing numerous criteria. Many approaches are available for solving environmental problem with multiple criteria, including the AHP method (Haastrup et al., 1998, Chiou and Tzeng, 2002, Tran et al., 2002), outranking methods (Brans and Vincke, 1985, Roy, 1991, Geldermann et al., 2000), and the TOPSIS method (Hwang and Yoon, 1981).

In recent years, MSWM models have stressed “sustainability,” and can be divided into two categories. One model category addresses social factors in the decision making methods (Beccali et al., 1998, Vaillancourt and Waaub, 2002, Klang et al., 2003), whereas the other model incorporates public participation into the decision making process (Bellehumeur et al., 1997, Vasseur et al., 1997, Ananda and Herath, 2003). Morrissey and Browne (2004) proposed that a sustainable MSWM model should be environmentally effective, economically affordable and socially acceptable. Wilson et al. (2001), who interviewed 11 different leading-edge European municipal solid waste programs in nine countries, proposed that “including different public groups in the process from the very beginning can help avoid the high levels of controversy and public opposition that have surrounded many MSW projects”.

Public participation in a decision-making process can occur at one of three stages: scoping stage, a decision-making stage, and a policy active stage. Most research efforts have incorporated public participation into the scoping and policy active stages by utilizing policy education and public meetings. In these models, the public is only apprised or takes part in the discussion, and has little effect on decision-making outcomes. Few studies integrate public participation into the decision-making process; in these studies, MCDM methods are typically applied. In previous MCDM methods, two processes must be completed before obtaining a final solution (Bryson, 1996): the consensus process and the selection process. The consensus process addresses how to obtain maximum consensus or agreement among experts or stakeholders for a set of alternatives; whereas the selection process determines how to acquire a solution set of alternatives from expert opinions regarding alternatives. The public’s involvement in the consensus processes is typically in weight setting. All methods seek a compromise solution among criteria, not between stakeholders. However, the source of conflict arises from the complex web of values held by stakeholders. Such conflict impacts the feasibility of implementing a decision. Although some studies have discussed the concept of consensus in relation to MCDM methods (Bryson, 1996, Tavana et al., 1996, Bordogna et al., 1997, Herrera et al., 2003, Chiclana et al., 2004), their focus has been on how to gain consensus, performance or decision.

This study presents a sustainable decision making-model that integrates the MCDM and consensus analysis model (CAM) for MSWM. The CAM is built up to aid decision making in traditional MCDM methods and to assess the degree of consensus between stakeholders for specific alternatives. The novel sustainable decision making model presented in this study has the following goals: (1) assist policy-makers when considering social aspects; (2) understand the degree of consensus among stakeholders regarding particular alternatives; and (3) help decision makers resolve potential conflicts during the decision-making stage.

The rest of this paper is structured as follows. Section 2 describes CAM, Section 3 then presents a sustainable decision-making model for waste management, and Section 4 discusses the food waste management system in Taipei City in Taiwan. Conclusions are drawn in Section 5, and several advantages of the proposed model are pointed out.

Section snippets

Consensus analysis model (CAM)

This study proposes a novel approach for quantifying the degree of consensus and consensus results for stakeholders in an attempt to find a compromise solution between the stakeholders. The “degree of consensus” denotes the degree of similarity of preference between stakeholders and the “consensus results” signifies the average preference of all stakeholders. Fuzzy set theory is introduced to deal with linguistic variables in the CAM. The opinions of each stakeholder are investigated using a

A novel sustainable decision making model for waste management

This study presents a novel sustainable decision making model for MSWM. Fig. 3 displays the outline of the algorithm, and the main steps are as follows.

Illustrative example

The novel sustainable decision-making model of waste management is applied to evaluate a food waste management problem in Taipei City, Taiwan. Taipei City’s population density is the highest in Taiwan. Food waste as defined here includes household kitchen waste and food waste from restaurants, markets and schools. Food waste comprises about 40% of Taipei’s municipal solid waste (MSW); the total food waste generated daily in Taipei City is 1316 tons. Recycling food waste will result in a

Conclusion

The novel sustainable decision-making model is a combination of MCDM and CAM. The proposed model provides an effective means of assisting decision making for real world waste management problems. The CAM can quantify degree of consensus and consensus results for stakeholders perspectives regarding alternatives and identify the source of possible conflicts. The sustainable decision-making model not only accommodates economic, environmental and social factors simultaneously, but also incorporates

Acknowledgements

The authors thank the Bureau of Environmental Protection of Taipei City, Taiwan for financially supporting this research. The authors also thank the anonymous reviewers and the editor for their constructive suggestions.

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