Exergy Analysis: A Guide to Sustainability?

This paper argues for a continuing exploration of Nature’s organizing principles that sustain prolonged homeostasis of the earth’s ecosystems punctuated by forceful transitions to new emergent states. Ecosystems develop and maintain a dynamically stable state by transacting energy and materials with the surrounding flows to keep reversing their continual fall to the ground state. Conversely, the elevation of any component of the ecosystem above the ground level may be regarded as a measure of its functional efficiency. This measure, called exergy, can be calculated for an eco-subsystem based on knowledge of the energy and material fluxes that thread it and, most importantly, of where the ground level happens to be. Admittedly, it is not straightforward to quantify these figures, and the departure of assumptions from reality will inevitably translate into errors in the calculated exergy figures. However, the variance may be estimated by analysing the results of an ensemble of calculations with randomly perturbed input values. Even with these limitations, however, a map of exergy losses characterizing different parts of an ecosystem has the potential to reveal relative thermodynamic efficiencies for appropriate ameliorative interventions.