Sankey and Grassmann diagrams for mineral trade in the EU-28

Abstract

Material flow analysis is a key tool to quantify and monitor natural resource use. A very visual way to undertake such analyses representing the mineral trade of a certain nation or continent is through the well-known Sankey diagrams, in which the mineral resources that are extracted, imported, exported, recycled and consumed within the given boundaries are represented with the arrows proportional to their respective quantities. Yet Sankey diagrams alone are not sensitive to the quality of the resources as they only reflect tonnage. This issue can lead to misleading conclusions and thereby ineffective resource policies. A way to overcome this deficiency is using Grassmann diagrams instead, in which instead of tonnage the flows are represented in exergy terms, thereby accounting for the physical value of minerals. In this chapter we use the exergoecology method to evaluate mineral trade and foreign dependency in EU-28 for the 1995–2012 period. Using the year 2011 as a case study, we can see that 45.8% of the total input tonnes of minerals are imported resulting in low values of self-sufficiency (Domestic Extraction to Domestic Material Consumption ratio). With data expressed in exergy replacement costs we can better reflect the real material dependency, 0.45 for minerals and 0.41 for fossil fuels, in contrast to 0.79 and 0.52 obtained respectively when using tonnes. Analyzing 10 of the 20 minerals considered critical by the European Commission, imports represent 6.74% of the total imports while extraction represents only 3.19% of the total extraction. This external dependency leaves Europe in a delicate situation regarding fossil fuels and non-fuel mineral supply and highlights the importance of recycling and the search for alternative sources.