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Thermodynamic rarity (TR) is an indicator of raw material scarcity based on physical
aspects of the minerals where the different elements are produced . A given element has a high thermodynamic rarity value when it is scarce in the crust and/or when the processes required to mine and beneficiate it are very energy intensive. It is defined as the amount of exergy that would be required to extract and beneficiate an element from ordinary rocks (i.e. not from ore), using the best prevailing technologies. Thus, TR is composed by two terms:
To calculate the TR of a device, it is necessary to know its elemental composition (in g), i.e. the mass of each element it embodies. The 𝑇𝑅 [𝑘𝐽] of a device will be the sum of all the individual contributions of the individual elements in thermodynamic rarity terms, as indicated by the following equation, where 𝑤𝑖[𝑔], refers to the mass of each element in grams, and TR_i [kJ/g] the thermodynamic rarity of each element (provided by the calculator) .
The following figure shows an example.
Total composition (g)
Ortego, Valero, and Restrepo (2018).
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