The authors and editors of this volume state that with the intensive growth of global industrialization and urbanization, the consumption of various resources and materials, such as energy, minerals, and even water, is increasing at an amazing speed, which poses great pressure on material resources. In addition, the massive utilization of materials has led to low efficiency, resulting in great wastes of resources as well as serious environmental pollutions and degradation, which has severely hindered the sustainable development of economy and society. In order to transit to sustainable development, it is necessary to improved resource efficiency, and circular economy and waste valorization are the best alternative ways for achieving this goal. This book aims to provide an in-depth description of circular economy and waste valorization, make assessments for circular economy and waste valorization in different regions and countries and determine the technological pathways and roadmap for achieving circular economy and waste valorization. More specifically: (1) Conceptions and Theories: Concepts and definitions of circular economy and waste valorization and their nexus and contributions to sustainable development. (2) Policy and Practice: Measurement and assessment of performance or sustainability for implementing circular economy and waste valorization. (3) Pathways and Prospects: Identification and prioritization of the barriers, strategies, technologies, and pathways for achieving circular economy and waste valorization. The book systematically and comprehensively introduces the definitions, concepts, framework and nexus of circular economy and waste valorization, analyzes and measures their performance and sustainability and provides the methods for investigating and prioritizing the barriers and strategies and determining the pathways and roadmap for their development.