In its methodological guides, EUROSTAT advises to distinguish various types of material flows according to the following scheme:
Direct versus indirect:
Direct flows refer to the actual weight of the products and thus do not take into account the life-cycle dimension of production chains. Indirect flows, however, indicate all materials that have been required for manufacturing (up-stream material requirements) and comprise both used and unused materials.
Used up-stream material requirements of traded products should be expressed in so-called "Raw Material Equivalents (RMEs)", which express the amounts of used primary extracted materials required along the whole production chain of an imported or exported product.
Used versus unused:
The category of used materials is defined as the amount of extracted resources, which enters the economic system for further processing or direct consumption. All used materials are transformed within the economic system. Unused extraction refers to materials that never enter the economic system and comprises overburden and parting materials from mining, by-catch from fishing, wood and agricultural harvesting losses, as well as soil excavation and dredged materials from construction activities.
Domestic versus Rest of the World:
This category refers to the origin and/or destination of material flows, as materials used by the economy can either be extracted from the domestic territory or imported from other countries. Note that for the categories of unused and indirect material flows related to internationally traded products, the terms „ecological rucksacks" and „hidden flows" are also used.