Identify stakeholders' understandings of life cycle assessment results on wastewater related issues.

To facilitate decision-making processes in waste management, it is important to not only evaluate environmental impacts, but also to measure how stakeholders form opinions and make choices based one valuation results. Life cycle assessments (LCAs) have been widely used to evaluate environmental impacts; however, LCAs cannot be used to measure how people make judgments based on evaluation results. As such, in this study, we combined LCA with conjoint analysis, an economic method that allows individuals to consider all factors and demonstrate their preferences simultaneously. We used this combined method in a case study on wastewater treatment, and obtained two major types of estimation results: (1) the relative importance of each impact category of LCA, and (2) the overall preferences of respondents for each alternative. This study also highlighted some issues regarding the combination of methodologies, such as the selection of impact categories in LCA, the conversion of impact categories into understandable attributes for conjoint analysis, and weaknesses in conjoint analysis that need to be addressed and corrected in future studies.