Sankey Diagrams

I was pointed to an article on carbon footprint, that used Sankey diagrams to underline a method of carbon accounting along the supply chain. This article was part of the “first virtual global conference on climate change” CLIMATE 2008 that took place, yes, exclusively on the Internet from November 3 to 7, 2008. (I must admit that this event passed largely unnoticed by me, although reading some of the papers now gives me the impression that it would have merited more attention.)

The paper titled “Carbon Accounting and Carbon Footprint - more than just diced results?” by Prof. Mario Schmidt from Pforzheim University describes the various approaches of corporate carbon accounting, carbon footprint of products, and Life Cycle Assessment LCA. Schmidt introduces a method that allows determining “cumulative emissions … at each point of the supply chain up to the POS”, and calls this the CO2 backpack.

The four Sankey diagrams above from the article illustrate the idea. They show (1) the CO2 equivalent emisisons along the supply chain, (2) the value added in a supply chain, (3) the relative CO2 emissions per value of product, and (4) the total emissions of the products along the supply chain with sectoral gate-to-gate, cradle-to-gate or crade-to-grave approaches.

This article is well worth reading, you should do so while it is still available online.
Schmidt is an acclaimed expert in Sankey diagrams and has also published on the history and methodology of Sankey diagrams.

A two-part article on ‘The Sankey Diagram in Energy and Material Flow Management’ was published in the Journal of Industrial Ecology (JIE). The author, Mario Schmidt is a professor at Pforzheim University in Germany. The first part focuses on the history of Sankey diagrams, while the second centers on ‘Methodology and Current Applications’.

Abstracts and links to the full articles are available at the publisher’s website.

Mario Schmidt (2008) The Sankey Diagram in Energy and Material Flow Management. Part I: History Journal of Industrial Ecology 12 (1) , 82–94 doi:10.1111/j.1530-9290.2008.00004.x

Mario Schmidt (2008) The Sankey Diagram in Energy and Material Flow Management. Part II: Methodology and Current Applications
Journal of Industrial Ecology 12 (2) , 173–185 doi:10.1111/j.1530-9290.2008.00015.x

I am not a subscriber, but maybe someone with access to these publications wishes to post a summary comment.

Christian Behrens from the Department of Design at Potsdam University of Applied Sciences in Germany put up a website on Information Design Patterns. It features “design patterns that describe the functional aspects of graphical components for the display, behavior and user interaction of complex infographics”.

The website is modestly called an “application prototype” of a pattern browser, and is part of his Master Thesis titled “The Form of Facts and Figures”.

All patterns are tagged and can be searched. For each type he presents a fact sheet with description, usage, required data, and rationale. Christian provides an own example for each pattern, and a “real-world example” from an external source. Additionally, related diagram types are listed.

The Sankey diagram is A 5.1. The example shows the average income and spendings of a Berlin household in 2005. Salary, asset revenues and public subsidies make up for the total income, shown in green. The income is spent on taxes, housing, food, clothing and other, shown as orange arrows.

I do miss a number stating the total (3015 Euro, roughly 4500 US$) as a label for the magnitude in the middle, but nevertheless this is a superb example of information presentation with a Sankey diagram. Just try to imagine the same information shown as two pie charts…

Enjoy browsing the Information Design Patterns website.

Environment Canada in 2001 published a Pollution Prevention Planning Handbook, a 153 page guidance manual on processes and techniques for pollution prevention (full PDF here - large!).

In section B-7 of the handbook materials accounting and mass balances are presented as one technique. The text states that

materials accounting and materials mass balances can be presented in a tabular or diagrammatic format. A Sankey diagram provides one useful method for representing a picture of material flows and balances.

and a sample diagram is shown.

Although not all quantities of the individual flows are shown, and there is no reference to the unit used, I think this is a fine example of using Sankey diagrams. The mass imbalance at the first process “Presse” (at the very left) is clearly visible. From the neighboring downstream processes you can see that at least 2105 units (to “Trémie”) and 738 units (to “Évaporation”) leave the process, that has inputs of only 2616 units. The diagram was made with S.Draw.

Remember having to learn the elements of the periodic table back in chemistry class?

Visual Literacy now presents a ‘Periodic Table of Visualization Methods’ that has been published by two scientists from the University of Lugano in Switzerland.

Each elements represents a visualization method, from ‘C’ like ‘continuum’ to ‘Sd’ like ’spray diagram’. The Sankey diagram can be found as element ‘Sa’ in the periodic table. It is colored in green for being in the ‘Information Visualization’ category. Furthermore its characteristics are ‘Overview’ and ‘convergent thinking’.

You can see the full periodic table at visual-literacy.org and hover the mouse over to see an example for each visualization method. The original article (Lengler R., Eppler M. (2007). Towards A Periodic Table of Visualization Methods for Management. In: IASTED Proceedings of the Conference on Graphics and Visualization in Engineering 2007, Clearwater, FL, USA) and the table separately are available as PDF files.

Mario Schmidt, a professor at Pforzheim’s University of Applied Sciences has published a paper on Sankey diagrams and their use in material flow management. The article, entitled “Der Einsatz von Sankey-Diagrammen im Stoffstrommanagement”, has two main sections: In the first part the author reviews how and where this type of diagrams have been used since they first appeared in a publication by Capt. Riall Sankey. This section also contains numerous samples: Sankey diagrams displaying the energy efficiency of the steam engine and of a 1911 a race car, material flow diagram from the iron and steel industries and many others. In the second part Schmidt elaborates on the methodology of Sankey diagrams and explains how extensions to the original Sankey diagrams (e.g. for cost flows or for material stocks) can be made.

The article is in German (sorry folks!), but according to Schmidt he’s working on an English publication…