MIKADO: a decision support tool for pollution reduction in aluminium pressure die casting

Industrial activities cause a variety of environmental problems. These are largely caused by emissions of air pollutants, the production of waste and depletion of natural resources. As a consequence, industrial managers face a complex problem when assessing the overall environmental pressure on the environment, and options to reduce this pressure. This complexity is associated with the range of activities taking place in industrial processes, the variety and complexity of their environmental effects, the number of available technologies for pollution control, and the costs of pollution reduction. Despite this complexity, pollution reduction in industry is not always based on systematic analyses,noron clearly defined company priorities to environmental management. An important reason for this is a lack of integrated analyses of the environmental impact of industrial processes, the options to reduce this impact and the associated costs. An instrument to assist plant managers in deciding on environmental management is of utmost importance. However, a decision support tool that takes a company perspective and covers all relevant environmental issues as well as costs of environmental management is currently not available in the literature.The overall objective of the thesis is to develop a decision support tool to analyse options to reduce the environmental impact of an industrial company. A model is developed for the assessment of the potential environmental impact resulting from emissions of environmental pollutants, as well as the effectiveness of reduction options and the associated costs. The tool aims to take a company perspective and to assist the company management in the analyses of possible strategies to improve the company's environmental performance. An industrial plant, supplying the automotive industry with aluminium pressure die casting products, located inPortugal, served as case study.The following research questions are addressed: 

1)      What existing environmental systems analysis methods and tools can in principle be combined in a decision support tool and used to analyse the environmental performance of a plant from a company perspective?

Which technical pollution reduction options are available for reducing the environmental impact of an aluminium pressure die casting plant? What are their technical potentials to reduce this impact, and the associated costs for the plant?How can a model be developed that can be used from a company perspective to analyse options to reduce the environmental impact of aluminium pressure die casting?How do different strategies to combine pollution reduction options improve the environmental performance of an aluminium pressure die casting plant, and what are the associated costs for the plant?Environmental systems analysis (ESA) is often used to assist decision making in finding solution to complex environmental problems. A systems analysis research strategy is followed to address the above formulated research questions. It is based on a stepwise approach consisting of: 1) Problem definition; 2) Evaluation and selection of existing ESA tools; 3) Identification of pollution reduction options; 4) Model building; 5) Model application and finally 6) Evaluation of the methodological approach.In this environmental systems analysis, seven analytical tools are combined. These are selected on the basis of criteria ensuring an analysis that takes a company perspective; includes environmental and economic aspects of decision making; includes a complete coverage of the potential environmental impacts and allows for an assessment of the consequences of pollution reduction strategies. The associated characteristics of the decision support tool to be developed are that it i) considers a gate-to-gate approach; ii) considers the processes within the plant that are relevant for the assessment of the environmental impact; iii) uses plant specific data easily available from the process owner; iv) considers up-to-date and plant specific pollution reduction options; v) provides information on the cost-effectiveness of the reduction options; vi) can be used to express the environmental performance in one overall environmental indicator; and vii) can be used to explore possible user-defined pollution reduction strategies. Based on these characteristics the following analytical tools are considered useful for the purpose of this study: Life Cycle Assessment, Substance Flow Analysis, Multi-Criteria Analysis, Technology Assessment, Sensitivity Analysis, Scenario Analysis and Cost-Effectiveness Analysis.Next, 18 pollution reduction options are identified for the aluminium pressure die casting plant studied. For each option the potential to reduce the pollution and the costs associated with their implementation is estimated. The options include typical end-of-pipe solutions, as well as more structural changes in the industrial processes. The options are considered the best available for the current aluminium pressure die casting sector. The inventory shows that promising and effective opportunities exist for pollution reduction. A model (MIKADO) is developed for and applied to the specific aluminium die casting plant. MIKADO is the Model of the environmental Impact of an Aluminium Die casting plant and Options to reduce this impact . The model includes material and energy flows in the plant that give rise to environmental problems. It considers the following sub-processes: Melting; Casting; Finishing; Internal Transports and Auxiliary Burners. MIKADO can be used to analyse future trends in the potential environmental impact of the aluminium pressure die casting plant and the effect of different pollution reduction strategies, as well as the costs for the company. One of the strengths of MIKADO is the integrated approach that it takes in analysing, simultaneously, all the relevant environmental problems caused by the aluminium die casting plant.MIKADO results are first analysed for the situation that reflects the current practice in the plant. In addition, a partial sensitivity analysis performed to study the sensitivity of MIKADO results to changes in parameter values. The results indicate that more than 90% of the environmental impact of the company is from the sub-processes Melting and Casting. Moreover, the environmental impact caused by the plant is mostly associated with human toxicity problems (caused by metal emissions, and emissions of ozone precursors) and the depletion of natural gas. Four relatively larger sources of environmental pollution include the use of natural gas and emissions of hydrogen fluoride in Melting, and emission of chromium and non-methane volatile organic compounds from Casting. These four cause about two-thirds of the overall environmental impact. MIKADO results show to be relatively insensitive to the valuation factors used to assess the overall environmental impact.A systematic analysis of the pollution reduction options reveals that the potential to reduce pollution varies largely for the 18 options analysed. Individual options may reduce the overall environmental impact by up to 40%. The most effective single options, leading to the largest reductions, are found to be two wet scrubbers associated to Casting. The costs to implement reduction options differ largely. Six options have net negative costs, implying that the company may in fact earn money by implementing them. These include the use of a granular desoxidation agent, reduction of the scrap produced during Casting and Finishing, the use of electric forklift trucks in internal transport, a new mould release agent and compacting the metal load entering the melting furnaces. The last option is found to be the most paying.Seven different types of reduction strategies are analysed, assuming the simultaneous implementation of different pollution reduction options. These strategies, reflecting different environmental management objectives, are analysed with respect to their potential to reduce the environmental impact and the costs associated with the implementation of options. The strategies differ largely with respect to their effect on the environmental impact (10 - 87% reduction) and costs (-268 to + 277 kEuro/year). The most effective strategy is a combination of options to reduce human toxicity, but this is also a relatively costly strategy. The least effective is related to metal yield increase. Combining the most paying options is an interesting strategy: it reduces the overall environmental impact by 45% at negative net costs (-268 kEuro/year). Eleven strategies could be defined which reduce the overall environmental impact by more than 50%. Of these two have net negative costs. It is also possible to reduce largely the environmental impact in the case in which the costs of add-on techniques are compensated by benefits of the paying options. This is, for instance, the case when most cost effective options are combined. Results show a large reduction in the overall environmental impact (86% reduction), while the company gains 51 kEuro/year.Novel aspects of this thesis include: 1) the company perspective that it takes; 2) the involvement of plant managers throughout the research; 3) the environmental systems analysis research strategy (sequence of environmental systems analysis steps and iterations), and 4) the selection of environmental systems analyses tools.The company perspective taken when developing MIKADO is reflected by the definition of system boundaries, the production processes included and the pollution reduction options considered in the model characteristics. The decision support tool only considers the industrial processes that can be managed by the plant managers, as well as the different types of environmental problems that the plant contributes to (air emissions, liquid effluents, solid wastes and natural resources used within the plant gates).The involvement of plant managers during MIKADO development was essential for ensuring that the tool to support decision making fulfils their expectations on the assessment of the environmental performance of the plant. A major strength of the tool developed to plant managers is its flexibility. This flexibility contributes to the willingness of the plant manager to use MIKADO to analyse possibilities for environmental management in the plant.The research strategy taken in this thesis includes a unique sequence of steps and iterations and is considered the appropriate and useful for development of decision support tools for environmental management in industrial companies. The environmental systems analysis procedure followed here may also be useful in assisting environmental decision making by other industries.

Finally, the procedure to select analytical tools as a basis for the model was helpful. The detailed description of the procedure followed and the resulting combination of the analytical tools may serve as an example for other studies. This also holds for the combination of seven different environmental systems analysis tools, as presented in this thesis.