A Product-Level Approach to Historical Material Flow Analysis

Studies of material cycles, which have a solid history in biogeochemistry, include characterization of technological materials cycles that quantify the way in which materials move through the economy and environment of a region. One of the most important aspects of historical technological materials cycles is determining how much material goes into various uses over time and modeling its lifetime in each use. A material flow analysis methodology is presented by which a historical (i.e., 1975 to 2000) study of tungsten use in the United States was constructed. The approach utilized in this study is twofold: the traditional approach by which material going into end-use sectors is approximated (the "end-use sector model"), and a second approach by which end-use products are specifically addressed (the "finished product model"). By virtue of the latter method, a detailed historical account of a material's end uses was developed. This study shows that (1) both models present a detailed treatment of trade of finished products over time for a variety of highly disaggregated products, (2) the end-use sector model provides a method to combine quantitative and qualitative data about products in various sectors to estimate domestic production for a metal about which little is known in terms of its end uses, and (3) the finished product model produces detailed estimates of domestic production for a large number of highly disaggregated products.