The interoperability of exergy and Life Cycle Thinking in assessing manufacturing sustainability: A review of hybrid approaches

Today, the Life Cycle Assessment is now the most commonly employed tool for assessing the sustainability of products, processes and activities, both from an environmental, social and economic point of view. Exergy is defined by literature as the amount of useful work that can be derived from a real system when it is brought into equilibrium with its environment by a set of reversible processes under which the system can only communicate with it In the literature, it is considered an outstanding concept that can be applied in order to enhance the effectiveness of ordinary evaluation models such as LCA. The purpose of the paper is to carry out a systematic review of the methodologies that imply the combination of exergy with life cycle thinking to assess sustainability in manufacturing. The concept of the Exergy-based approaches has been widely established in literature, as shown by the vast number of academic papers and books published so far. The same may be said for LCA, with the additional benefit that there are software resources as auxiliary tools. The literature proposes different hybrid approaches that combines exergetic analysis with LCA with different level of integration or combines costs and environmental impacts in exergetic terms. There are, however, drawbacks that seem to be too challenging to overcome: a variety of inconsistencies in the interpretation of the results due to the difficulty of the inventory phase and the ambiguity in the choice of the correct alternative in the standard databases; the link with old techniques that refers to obsolete approaches in finding data that suit to the updated goals and scopes; the difficulty in conducting an assessment affected by the least possible uncertainty. The fascinating fact that emerges from the review is that any approach mentioned in the paper will be more successful if it were joined (not replaced) to the standard LCA, because it turned out to be complementary in such a way. Specifically, the outcomes together will describe a transdisciplinary structure for the behaviour of the study case system. This theory has long been developed by many authors in their case studies as a confirmation of what Gutowski wrote years ago: no single alternative criteria or subsidiary model, independently of how well aggregated, may offer a suitable answer for all conditions.