Summary: The Sankey diagram is an important aid in identifying inefficiencies and potential for savings when dealing with resources. It was developed over 100 years ago by the Irish engineer Riall Sankey to analyze the thermal efficiency of steam engines and has since been applied to depict the energy and material balances of complex systems. The Sankey diagram is the main tool for visualizing industrial metabolism and hence is widely used in industrial ecology. In the history of the early 20th century, it played a major role when raw materials were scarce and expensive and engineers were making great efforts to improve technical systems. Sankey diagrams can also be used to map value flows in systems at the operational level or along global value chains. The article charts the historical development of the diagrams. After the First World War the diagrams were used to produce thermal balances of production plants for glass and cement and to optimize the energy input. In the 1930s, steel and iron ore played a strategic role in Nazi Germany. Their efficient use was highlighted with Sankey diagrams. Since the 1990s, these diagrams have become common for displaying data in life cycle assessments (LCAs) of products. Sankey diagrams can also be used to map value flows in systems at the operational level or along global value added chains. This article, the first of a pair, charts the historical development. The companion article discusses the methodology and the implicit assumptions of such Sankey diagrams.

What potentials do manufacturing companies have for identifying inefficiencies in their use of resources? Assessing the products with regard to their durability, functional usefulness, use of materials, etc. is only one aspect of the exercise. The actual production operations and the search for in-plant inefficiencies represent the other. In Germany, the material flow cost accounting (MFCA) method was developed years ago to tackle this requirement. It evaluates material losses in the company in monetary terms and thus points up the economic benefit of resource efficiency. MFCA first achieved practical relevance and large-scale application in Japan. Now there is even an ISO standard on the method. The article outlines the process and presents typical examples. It explains how a methodological bridge can be built to assess the loss of material in ecological terms too.

Metals are an essential part of modern living. Ensuring the future supply of metals is a key issue in politics, science, and economics because the available amount of mineral resources is limited. To measure the depletion of mineral resources, several indicators are used. Some of them are based on the ore grade, which has been decreasing over time and is thus taken as a sign of resource exhaustion. However, does this assumption hold true? This paper shows that the development of ore grades is mainly the result of the increasing demand and the outstanding technological improvements that made mining of low grade ores profitable. The usage of ore grades as an indicator may, therefore, lead to erroneous conclusions about the safeguard objects. These are not the metals themselves, but the environment that is impacted by their extraction.

Copper has always played an important role in human development. Demand for copper is going to rise, which makes its future supply a key issue for society. However, the oft-discussed declining ore grade and, therefore, the assumed enormous increase in energy demand and global warming potential could lead to a supply constraint. To develop suitable strategies to ensure copper availability, it is important to better understand the relationship between energy and ore grade and also its development. Therefore, in this paper we describe the development of the cumulative energy demand of copper production over the last eight decades and give an outlook into the future using a holistic process-based modelling approach. We also discuss how technological progress has thus far been able to offset the decreasing ore grade. However, if geological factors are becoming less favorable, technological improvements such as renewable energies are vital to keep this trend going.