4.3. Tracking Material Flows in Engineered Systems

Materials have a life cycle. They are extracted from the lithosphere or biosphere, processed into commodity materials, then products, then used and possibly reused, then eventually disposed of or leaked into the environment. The number of times that a material is reused or recycled before it is released into the environment can have a significant impact on its environmental footprint. In addition, different types of uses, for the same material, can lead to very different types of impacts.

Characterizing the flows and emissions of materials in manufacturing and use requires data on material and mineral flows entering the economy, and information on the wastes, emissions, and recycling structures. Data that enable this new generation of analyses are just emerging. Therefore, terminology and data analysis frameworks are still evolving. One set of terminology is shown in Figure 4-5.