This presentation from 2015 by Alicia Valero of the Spanish Research Centre for Energy Resources and Consumption (CIRCE, Zaragoza) is on critical materials, minerals scarcity, recycling and a “thermodynamic cradle-to-cradle approach”.

It features two Sankey-style diagrams depicting the mineral balance of the European Union (UE).

This first one is a Sankey diagram for the mineral balance without fossil fuels (‘Diagrama de Sankey para el balance mineral de la UE sin combustibles fósiles’).

Data is for the year 2011, Flows are shown in tons. Iron and limestone dominate the picture with 77% of the input. Limestone is produced (extracted) mainly within Europe, while iron is mostly imported.

The second Sankey diagram is a scarcity diagram (‘Diagrama de rareza para el balance mineral de la UE sin combustibles fósiles’) and takes into account thermodynamic exergy to obtain (mine) the minerals. Although it depicts aluminium, gold, ion, nickel and the likes, flows are shown in an en(x)ergy unit (Mtoe).

Iron and limestone which seemed to be the most important mass-wise only constitute some 10% of the input. Aluminium and potash seem to be much more difficult to produce. Rare earth elements (REE) are not included in this diagram.

The author points out that it is important to not only look at materials from a mass perspective. Looking at materials availability taking into account thermodynamic exergy paints a different picture of the real cost and scarcity.

For those interested, please check out the presentation (in Spanish) here.

While brosing this presentation by Thomas E. Graedel, Yale University, Center for Industrial Ecology with the provocative title ‘Rare Earths and Other Scarce Metals: Technologically Vital but Usually Thrown Away’ I discovered the following distribution (aka alluvial) diagram. It was originally published in the article ‘Uncovering the end uses of the rare earth elements’ by X Du, TE Graedel in Science of the Total Environment, 2013 (pp. 781-784)

The diagram is best read from right-to-left: The right column shows ten rare earth elements (REE) and a node for the “other” five or seven REEs. Lanthanum (La), Cerium (Ce), and Neodymium (Nd) make up the largest portion mass-wise, followed by Praseodymium (Pr) and Yttrium (Y).

The middle column nodes (categories) represent technological uses of these REEs in e.g. magnets, automotive catalysts, or polishing powders.

The left column then represents the countries or regions where the components or products that contain REEs are produced: China, Japan, and the United States.

Data is for 2007. No mass unit or absolute numbers given for the diagram in this presentation, and I presently don’t have access to the original publication.

Du and Graedel have also published an interesting paper on ‘Uncovering the Global Life Cycles of the Rare Earths Elements’ where they analyse REE from mining to end-of-life with losses along the life cycle and display these data in a circular flow diagram for each REE. These “REE wheels” also call for a Sankey representation, but that will be for another time…