Assessing the Reliability of Material Flow Analysis Results: The Cases of Rhenium, Gallium, and Germanium in the United States Economy

Decision-makers traditionally expect
“hard facts”
from scientific inquiry, an expectation that the results of material
flow analyses (MFAs) can hardly meet. MFA limitations are attributable
to incompleteness of flowcharts, limited data quality, and model assumptions.
Moreover, MFA results are, for the most part, based less on empirical
observation but rather on social knowledge construction processes.
Developing, applying, and improving the means of evaluating and communicating
the reliability of MFA results is imperative. We apply two recently
proposed approaches for making quantitative statements on MFA reliability
to national minor metals systems: rhenium, gallium, and germanium
in the United States in 2012. We discuss the reliability of results
in policy and management contexts. The first approach consists of
assessing data quality based on systematic characterization of MFA
data and the associated meta-information and quantifying the “information
content” of MFAs. The second is a quantification of data inconsistencies
indicated by the “degree of data reconciliation” between
the data and the model. A high information content and a low degree
of reconciliation indicate reliable or certain MFA results. This article
contributes to reliability and uncertainty discourses in MFA, exemplifying
the usefulness of the approaches in policy and management, and to
raw material supply discussions by providing country-level information
on three important minor metals often considered critical.