Energy and Environmental Tools for Process Sustainability Evaluation

The aims of this thesis are the development of theoretical approaches and their application to real cases in order to assess the sustainability of production processes. Adopting an approach of Life Cycle Thinking allows to compare different technologies, both traditional and innovative ones, evaluating the best performance from an energy and environmental perspective. Currently there are many technologies that are presented as sustainable at the theoretical level. However there are actually insufficient tools to verify that technologies are truly sustainable, not only at the theoretical level and considering not only the final stage of the operation, but the entire life cycle. Moreover there are insufficient tools for ranking technologies on the basis of their sustainability. In order to select the most efficient technology, the question is: "Which criteria can be used for selecting the most appropriate technology?". The present thesis proposes instruments to answer that question: the Analogical Model, EROI (Energy Return On Investment) and EPT (Energy Payback Time), SEI (Environmental Sustainability Index). The uncertainty is treated in a dedicated chapter. The first section of the thesis is dedicated to a theoretical analysis of those arguments, which are applied in the second section in four case studies. The first case study is dedicated to the Dark Anaerobic Fermentation in two stages: hydrogen and methane are produced using waste organic materials as substrate. The second one illustrates the comparison between four prototypes of nano-structured heat exchangers and a traditional heat exchanger (Thermonano European Project). The third one shows the design of the artificial leaf by applying a sensitivity analysis to find out the direction to follow for future developments (Solhydromics European Project). Finally, the fourth one describes a study in which energy and environmental impacts of a typical workday are compared by evaluating dietary and transport.