Life cycle energy sustainability assessment: an expanded framework for energy technologies

Abstract

Life Cycle sustainability assessment is one of the most relevant tools delving in sustainability science, based currently on the triple bottom line idea, that is identified in the use of the three tools of Life Cycle Assessment (LCA), Life Cycle Costing (LCC) and Social Life Cycle Assessment (S-LCA). The methodology is structured on international regulations and is currently being applied to a wide set of products and systems. However, when targeting specifically energy technologies with this methodology some specific issues need to be taken in consideration before applying tout court the standard LCSA methodology. Energy systems – in particular those where fluid streams are used – have an understanding depth that cannot be currently investigated with the available tools, thus having only a partial understanding of the problem. This paper proposes to develop an extended framework for LCSA introducing two additional stages to the theory, to address the limits highlighted in the previous paragraphs: Constructal law (CL) inspired analysis of the energy design of the system and exergy analysis (EA) of the system and its life cycle. A fully developed case study (a biomass boiler) is proposed, described in all five stages of the extended Life Cycle Energy Sustainability Assessment: LCA, LCC, S-LCA, CL, EA, highlighting both the quantitative results related to each section and the strengths and limits of the methodology, while stressing the potential applications as e.g. decision support tool and support to the design of energy system. The results highlight different and optimized designs for the boiler through a Constructal law based analysis and several hot-spots throughout different stages of the life cycle, ranging from the production stage of steel for most environmental indicators in LCA to the cooking stage for the exergy analysis. Relevant positive impacts are traced also in the S-LCA point of view during both the use and production step.