Reconciling Consumption and Conservation: Using An Exergy-based Measure of Consumption to Strengthen The Conceptual Framework of Industrial Ecology

Efforts to reduce resource depletion have intensified in recent years with the emergence of a new field of study called industrial ecology (IE). IE proponents seek to use the evolution of biological ecosystems as a model for reducing resource depletion in industrial systems. Although the IE literature offers an important set of goals and organizing principles for reforming industrial activities, as a field of study IE remains unexplored and ambiguous on several levels. One "core" philosophical deficiency is the lack of a physical interpretation of resource consumption and associated ambiguity about the roles and limitations of resource conservation strategies such as waste cascading and recycling. The purpose of this dissertation is to demonstrate that the form and significance of the ecosystem analogy at the core of industrial ecology may be greatly strengthened by using the property exergy ­ a measure of accessible work potential ­ to define resource consumption as exergy removal. An exergy-based definition of consumption provides a basis for developing an exergy-based definition of resource cycling ­ the cycling of material exergy (CME) ­ that differentiates among full and partial cycling, recirculation, and cascading of consumed resources. Defining consumption as exergy removal also provides a basis for developing a thermodynamic interpretation of ecosystem evolution as a process of allowing resource consumption to occur with decreasing levels of resource depletion ­ i.e. a process of "de-linking" consumption from depletion. I express resource depletion rate as a product of consumption rate and the Depletion Number, a non-dimensional indicator of depletion per unit consumption that provides one measure of ecosystem progress on an evolutionary scale. I then use the Depletion Number as a focal point for developing an analytical framework that characterizes the highly interdependent roles of cascading, cycling, efficiency gains, and renewed exergy use in de-linking resource consumption from resource depletion. To depict resource flows and quality variations in resource cycling networks, I introduce an exergy-based "flow quality diagram." I then use this diagram and the associated analytical framework to analyze strategies for depletion avoidance in idealized aluminum beverage container and benzene cycling networks.

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Catherine P. Koshland Wood-Calvert Professor in Engineering Professor, Environmental Health Sciences, and Energy and Resources University of California, Berkeley