Cyclic Flow of Material: Concepts and Classifications

Resource shortages and environmental deterioration are primarily attributed to the disturbance caused by human activities beyond the natural capacity, and the primary purpose of human activity is to satisfy the material and cultural demands of people, which means that the primary object of human activity is “material.” By using material resource processing, transformation, transportation, and other social and economic activities, the service goal of human demands can be satisfied. Therefore, improvement of resources and the environment should first focus on the “material” flow. What is the flow of material? What are the basic laws of material flow? How can we assess the flow state of material? How can we optimize and manage material? These issues are the theoretical basis for the circular economy development and will be discussed separately in the next three chapters.