A Framework for Computer Aided Modeling, Design, and Optimization of Integrated Industrial Systems
The current societal-industrial system is unsustainable in that it consumes and emits vast quantities of raw materials and energy with little consideration of the long-term effects on humanity and eco-systems. The scale of human activities has reached the same order of magnitude as the scale of the earth’s ecosystems and resources, thus creating the potential to significantly alter the earth to the detriment of future generations. Thus if society is to prosper in the long term, it is necessary to better understand and control the effects of humankind’s actions on itself and the environment. The needs and wants of human societies are met through the actions of industry. Thus, a key point in progressing towards a sustainable society is finding means to reduce the environmental load of industrial activities. Current industry functions under the market system, which implies that the primary design consideration of industrial systems is the maximization of profit. Thus, how to progress towards sustainable industry in the context of the market system is a crucial question. One approach to addressing this issue is the integration of industrial
activities.
As human knowledge progresses, we gain a greater understanding and ability to manage complex systems. In the context of industry and sustainability, Industrial Ecology (Frosch and Gallopoulos 1989), Industrial Metabolism (Ayres 1994), and Zero Emissions (Pauli 1996) have recently come forward as approaches addressing how a systems viewpoint can address the issue of sustainable industry. The common theme in these approaches is to look beyond the individual processes of extraction, manufacture, consumption, and re-use to consider how they link together to form a system. A typical industrial system today is “open”, meaning that materials and energy are taken in and disposed of freely, the main constraint being the minimization of cost for producing a given product. Such open systems generally only utilize a small fraction of the input materials and energy, to progress towards sustainable industry there is clearly a need to “close” the system as much as possible. An important component of closing the cycle of materials and energy is the integration, or clustering, of industrial activities. Integration in this context is the linking of industrial processes such that interconnected whole utilizes materials and energy effectively and emits minimal waste. The key point is how outputs of a given process can be used as input for other processes, instead of being dumped or emitted and thus becoming waste. An especially attractive aspect of such linking is that as in many cases finding a use for wastes generates economic value, it has potential to increase profitability as well as reduce environmental impacts. Zero Emissions emphasizes this value-added use of outputs as inputs as a key to creating “industrial clusters”, which are groups of industries linked together in symbiotic relationships to minimize waste and maximize profitability.
There is some tendency for industrial systems to self-organize towards integration, as evidenced by many examples of industries selling unused “wastes” for use in other contexts. Generally, these points of connection were established through bilateral recognition of the economic advantages between the two parties involved in the relevant processes. An example of where this bilateral self-organization has resulted in a high level of integration occurs in the industrial district at Kalundborg, Denmark (Ehrenfeld 1997). However, looking at industry overall, the average degree of integration would appear to be rather low in comparison with its potential. In addition to bilateral self organization of integrated industries, which proceeds without any overall plan, it is important to consider the potential for achieving integration through careful organization of the system. This planning could be done through a multilateral process involving different parties, and/or through one or two parties having control over a series of processes. The modern oil refinery is an example of sophisticated process integration within a given industrial sector. Controlled design presents improved possibilities for discovering the economic and utilizational advantages of integration, as in many cases benefits will be realized not just at the exchange point of two processes, rather from a more holistic view of the system.
The integration of industrial systems is a compelling idea, but how to progress towards realizing this potential in practice? Implementation requires, along with a concept, an appropriate “infrastructure”. For instance, Just-In-Time manufacturing, now viewed as almost an essential technique for cutting costs in the automotive industry, would be but a fanciful idea without the production and inventory monitoring systems, communications infrastructure, and management mechanisms needed to implement it. In the present case, there is a need for a bridge between the concept of integration and practical designs for integrated clusters. The focus of the current work is to contribute to developing techniques for modeling industrial systems and designing them towards integration. The modeling system, as in the Life Cycle Analysis (LCA) (Curran 1996) of products, uses input/output tables and system process diagrams to calculate the flow of materials and energy of an industrial system. It will in general be implemented via a computer and provides quantitative information on the economic and environmental performance of a given industrial system, either existing or planned. The model is to be used in conjunction with a design system, wherein computer algorithms search process databases to find possible links between industries. Given a set of possible links, computer algorithms optimize process composition and size for minimal waste and maximal profit.
When addressing the issue of sustainability, economics, resource utilization, and environmental impacts are essential components, but it is also important to consider effects on society as well. The larger issue of what are the benefits and costs a given industrial system has on society as a whole is of course very complex and varies according to the value system applied. However, a more limited, yet very relevant question can be addressed. To what extent does the activities of an industrial system directly provide income to support human life? Concretely speaking, how many people are supported at roughly at what level? This societal aspect is also to be included in the modeling framework.
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