Exergy assessment of mineral extraction, trade and depletion

AutoresCalvo Sevillano, Guiomar
Año publicación2016


Natural resources, especially minerals, are present in all products and are a vital component of society. Mineral consumption is experiencing an exponential increase and hence future availability is now playing a major role in resources efficiency policies. For this reason it is fundamental to have the best possible tools, objective and rigorous, that can help to properly account for this loss of resources. Studies cannot only be centered in analyzing current consumption patterns and reserves as it is happening now, but they need to take into account the gradual loss of future availability of resources due to mineral dispersion and the criticality of each of the materials. By means of the Second Law of Thermodynamics, through property exergy and with a so-called Physical Geonomics approach, mineral extraction and dispersion can be assessed. Exergy, traditionally used to assess energy resources, can be also used to account for non-energy minerals. The advantage of this approach over other conventional ones is that it takes into account not only the quantity but also the quality of the given resource.

Moreover, it is totally independent of monetary variations, thereby providing more accurate and objective information. Additionally, using this approach, one can easily cross over from the physical to the economic level, linking Thermodynamics with Economics, something that has been largely sought by the school of Ecological Economics. As the basis of Physical Geonomics model was already established in previous studies, the first task of this PhD Dissertation has consisted on improving the available data. For this endeavor, an analysis on real data on energy consumption from different mining industries was performed to obtain new and more accurate data on energy consumption as a function of ore grade. Additionally, using the available information of fossil fuel and electricity consumption over the years, several energy intensity factors have been calculated. The general trend observed is that average ore grade slowly diminishes over time while energy consumption and production increases. Moreover, new data of exergy replacement costs for several mineral substances, meaning the exergy required restoring a resource from a complete dispersed state where no deposits exist to the physical and chemical conditions found in Nature with the available technology, has been calculated and has been added to the initial model. The second task of this PhD Dissertation has been to propose a new indicator (GDP/DMD) that can be used at global level and that can evaluate natural resource efficiency. This new indicator takes into account not only the quantities of materials that are consumed within a region but also the quality of those materials, being able to put the focus on scarcer and critical substances. With GDP/DMD we can have a better and more accurate assessment of mineral depletion and it can be used to enhance more effective actions in the policy making process.