A graphical representation for consequential life cycle assessment of future technologies-Part 2: two case studies on choice of technologies and evaluation of technology improvements

Purpose To construct future visions of how innovative technologies should be used in the envisioned sustainable society while being aware of system-wide environmental impacts, consequential life cycle assessment (c-LCA) is useful. To systematically evaluate the technologies being aware of uncertainties in the choice of technologies made in the future, in this article, we propose a novel graphical representation for theoretical range of impacts that contain results from c-LCA studies. This approach allows analyses of the consequences of technology introduction without conducting a detailed modeling of consequences. Methods We stand on an assumption that the future environmental impacts reduced by a new technology depends on (1) how much the efficiency of the technology is improved, (2) how much of the less efficient technology is directly and indirectly replaced by the new technology, and (3) how much product is needed in the envisioned future. The difficulty in c-LCA is that (2) and (3) are uncertain from various socioeconomic reasons that are often difficult to predict. By organizing the results from product life cycle assessments in a systematic way, the proposed methodology allows exhibiting the range of consequential changes in environmental impact associated with a technology innovation, taking into account those uncertainties on a plain coordinated by the amount of product needed in the future and environmental impact on the horizontal and vertical axes, respectively. Results Part 1 describes the methodological framework in detail, whereas Part 2 elaborates on the applications of the methodology. By taking transportation technologies assuming various energy sources in Taiwan, the choices of technologies and the evaluation of technology improvements serve as the case studies to demonstrate the application of the methodological framework. Conclusions By using the proposed method to organize the assumptions in c-LCA, discussions on different choices of technologies are made more systematic. In this way, stakeholders can focus on visions of future society, which lead to different choices of technologies.