Mass and energy flows are crucial for production and consumption, contributing to well-being and economic growth. They also come with unsustainable effects: environmental impacts, depletion, unbalanced development. In this course, we focus on the sustainability assessment of technology, and mass and energy flows. We focus on how to conduct sustainability assessment; how these assessments affect decision and policy making and the social debate; and the scientific basis we build upon, e.g. research paradigms and methodology.