Assessment of the circularity and renewability of materials through thermoeconomics and exergy. The case of metals from Printed Circuit Boards.

The circular economy driven by renewable energies is one of the keys to the sustainability of industrializedsocieties. However, the quantification of both circularity and renewability of materials is not trivial as it combinesboth material terms, usually measured in mass, and energy terms, measured in energy units. In this sense, the use ofexergy is proved as a solution, since materials can be evaluated through exergy cost and renewable energy throughexergy. Thus it is possible to assess both the circularity and renewability of materials using the single criterion ofexergy. This study uses the case study of metals embedded in a printed circuit board (PCB) to illustrate these ideas.It considers the extraction of metals, and the production and recycling of the PCB. The disaggregation of the exergycost allows to identify the destruction of exergy (irreversibilities) and the origin of the exergy either non-renewableand renewable. Thus, the results show that the circularity of the PCB circular economy is between 27.3 and 49.6% depending on the deployment of renewable technologies. In other words, in a circular economy cycle betweenthree quarters and half of the resources measured in exergy are destroyed. On the other hand, renewability, i.e. thepercentage of renewable irreversibilities lost in relation to the total is between 12.9 and 79.4%, depending on thedeployment of renewables. The use of renewable technologies improves both indicators significantly. However,better strategies are needed to increase these indicators to ensure the sustainability of production processes in thelong term.