After generating the system inventory, the next step in QSD links the mass and energy flows across the system's life cycle with quantitative sustainability indicators, the values of which can be used to track the progress toward or away from the stated project goals. This section discusses techniques to characterize system sustainability with respect to economic, environmental, human health, and social dimensions. These four categories are adapted from the tripartite conception of sustainability (economic, environmental, and social dimensions 97 ), explicitly considering human health as its own dimension to highlight its significance in the context of environmental technologies and its distinct characterization techniques. Generally, sustainability characterization follows the steps of indicator selection, indicator evaluation, and