Browsing by Author "Yaw, Gyekye"

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    Implementation of a goal programming model for solid waste management: a case study of Dar es Salaam – Tanzania
    (International Journal for Simulation and Multidisciplinary Design Optimization (IJSMDO), 2017) Lyeme, Halid; Mushi, Allen; Yaw, Gyekye
    In this research article, the multi-objective optimization model for solid waste management problem is solved by the goal programming method. The model has three objectives: total cost minimization, minimization of final waste disposal to the landfill, and environmental impact minimization. First, the model is solved for the higher priority goal, and then its value is never allowed to deteriorate. The model is solved for the next priority goal and so on until the problem is solved. The model was tested with real data for solid waste management system from Dar es Salaam city. The results determine the best locations for recycling plants, separating plants, composting plants, incinerating plants, landfill and waste flow allocation between them. Furthermore, the solution shows a high reduction of the amount of waste to the landfill and greenhouse gas emissions by 78% and 57.5% respectively if fully implemented compared to the current system.
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    Multi-Objective Optimization Model Formulation for Solid Waste Management in Dar es Salaam, Tanzania
    (ASIAN JOURNAL OF MATHEMATICS AND APPLICATIONS, 2017) Lyeme, Halid; Mushi, Allen; Yaw, Gyekye
    Solid waste management is a challenging problem in developing nations. The health and environmental negative implications associated with solid waste management are very serious particularly in the developing nations where a large percent of waste is dumped into open areas. These implications are essentially on climate change and global warming due to environmental problems. In this paper, a multiobjective optimization model is developed to address the conflicting objectives of cost minimization, minimization of final waste disposal to the landfill, and environmental impact minimization. The model follows a mixed-integer programming formulation and tested by data from selected wards in Dar es Salaam city. The output is the best location of recycling plants, separating plants, composting plants, incinerating plants, landfill and waste flow allocation between them. The solution shows a high reduction of the amount of waste to the landfill and greenhouse gas emissions by 76% and 55.2% respectively compared to the current system
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    Review of Multi-Objective Optimization Models for Solid Waste Management Systems with Environmental Considerations
    (Journal of Mathematics and Computer Science (JMCS), 2017) Lyeme, Halid; Mushi, Allen; Yaw, Gyekye
    This paper analyzes more than 50 papers with a limited area in the field of solid waste management systems and supply chain management, extending over mathematical models that include economic factors, as well as environmental and/or waste flow allocation. The review finds that there are a number of limitations to the current research in sustainable solid waste management systems. The narrow scope of environmental factors as constraints in the current models means that there is a need to go further and include new environmental metrics. The effective inclusion of environmental objectives in models with improved multi-objective approaches is a gap that needs to be filled. Furthermore, there are significant gaps in sensitivity analysis of models limiting the general applicability of the models. The paper concludes with promising new avenues of research that demand effective inclusion of sustainability into solid waste management system models.
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    Sensitivity analysis of multi-objective optimization for solid waste management
    (New Trends in Mathematical Sciences, 2017-11-08) Lyeme, Halid; Mushi, Allen; Yaw, Gyekye
    In this study, a sensitivity analysis of a multi-objective optimization model for solid waste management (SWM) for Dar es Salaam city in Tanzania is considered. Our objectives were to identify the most sensitive parameters and effect of other input data to the model output. Five scenarios were considered by varying their associated parameter values. The results showed that the decrease of total cost for the SWMsystem in all scenarios was observed compared to the baseline solution when the single landfill was considered. Furthermore, the analysis shows that the variable cost parameter for the processing facilities is very sensitivity in such a way that if you increase the variable cost then, there is a rapid increase of total cost for the SWM system and the vice versa is true. The relevant suggestions to the decision makers were also discussed.