Extending Lifecycle Exergy Analysis Beyond Resource Consumption

In this paper, we explore a reduced-order framework to predict the sustainability of a given system. The approach combines concepts from economic theory, thermodynamics, and the environmental sciences into a simple scheme that allows evaluation of system sustainability in terms of a small number of variables. The underlying hypothesis behind the work is that sustainability can be correlated to reversibility, and therefore should bear a relationship with transitions from an initial benign state. We propose evaluation along three dimensions: (i) physical; (ii) economic; and (iii) social. The measure of physical damage follows from the second law of thermodynamics, and specifically we show when and how second-law derived metrics (such as lifetime exergy consumption) can be extended to capture additional impacts. The measure of economic impact is derived by correlating physical transformations of objects with their relative economic value, specifically through use of input-output models that have been previously published in the literature. Lastly, we explore capturing social value through a proxy of indexed measures that correlate to the notion of a ‘social entropy’, which is suggested as an approximation for the deviation of society from a general state of well-being. We propose unifying all three of these approaches through a generalized framework, and thus suggest a simple but broad ‘sustainability performance’ metric. The paper concludes by discussing the challenges associated with widespread implementation, validation, and completeness of such a framework.