Purpose Few studies have examined differing interpretations of life cycle impact assessment (LCIA) results between midpoints and endpoints for the same systems. This paper focuses on the LCIA of municipal solid waste (MSW) systems by taking both the midpoint and endpoint approaches and uses LIME (Life Cycle Impact Assessment Method based on Endpoint Modeling, version 2006). With respect to global and site-dependent factors, environmental impact categories were divided into global, regional, and local scales. Results are shown as net emissions consisting of system emissions and avoided emissions. Materials and methods This study is divided into five segments. The first segment develops the LCIA framework and four MSW scenarios based on the current MSW composition and systems of Seoul, considering adaptable results from the hierarchy MSW systems. In addition, two systems are considered: main MSW systems and optional systems. Several "what if" scenarios are discussed, including various compositions and classifications of MSW. In the second segment, life cycle inventory (LCI) analysis is applied to define various inputs and outputs to and from MSW systems, including air (23 categories), water (28 categories) and land (waste) emissions, resource consumption, land use, recovered material, compost, landfill gas, biogas, and heat energy. The third segment, taking the midpoint approach, investigates the nine environmental impacts of the system and avoided emissions. In the fourth segment, this study, taking the endpoint approach, evaluates the damages, dividing the four safeguard subjects affected by 11 environmental impact categories of the system and avoided emissions. In these third and fourth segments, LCIA is applied to analyze various endof-life scenarios for same MSW materials. The final segment defines the differences from the results in accordance with the two previous life cycle assessment methodologies (the LCIA and interpretations with respect to midpoints and endpoints). Results and discussion With the respect to midpoints, Scenario 1 (S1) using 100% landfills (L) is the worst performer in terms of global (global warming and resource consumption), regional (acidification, human toxicity, and ecotoxicity), and local (waste: landfill volume) impacts. In terms of all impacts except global warming and waste, Scenario 2 (S2) using 64.2% L and 35.8% material recycling (MR) was found to be the most effective system. With respect to global-scale endpoints, S1 was the worst performer in terms of human health and social assets, whereas the other scenarios with MR were poor and bad performers in terms of biodiversity and primary production. With respect to regional-and local-scale endpoints, S1 was the worst performer in terms of human health, biodiversity, and primary production, whereas Scenario 4 (S4) using 4.2% L (only incombustibles), 35.8% MR, 28.5% biological treatment (BT), and 31.5% incineration (I) was the worst performer in terms of social assets. S4 was the best performer in terms of global-scale endpoints, ...
