This paper proposes an exergy-based approach to evaluating the sustainability of different information technology (IT) systems. In reviewing existing standards around IT sustainability, we find that most of these metrics are based on energy efficiencies. Thermodynamically, these metrics imply sufficiency of a first-law analysis. In this paper, we show that such metrics based on the first-law of thermodynamics are necessary but not sufficient for evaluating the sustainability of IT systems. We discuss how — within the context of sustainability theory — exclusively relying on first-law metrics implicitly assumes a narrow set of system boundary conditions, and we show using an exergy-based life-cycle analysis that various classes of IT systems violate these boundary conditions. Thus, we suggest the need for metrics that include a second-law component as well as a life-cycle view of the IT system. Having identified such a metric, we demonstrate applicability of the framework for a sample IT system. We conclude by reflecting upon additional research needs and challenges associated with widespread implementation of such a framework.

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