Resumen de Thermodynamic assessment of raw material use in passenger vehicles
Decarbonizing world economies is necessary to avoid the continuous increase of global temperature and its negative consequences for humanity. To get this ambitious target new advances in the fields of power generation with renewables and mobility with cleaner vehicles are being made. In the case of vehicles, these advances are being mainly focused on improving the performance of combustion engines, to reduce greenhouse and polluting emissions and the development of free direct emission vehicles like the electric ones.
Advances towards cleaner vehicles are encouraging the continuous renovation of vehicle fleet so it is expected that in the following decades a complete renovation will take place. This new generation of vehicles will significantly reduce its fossil dependency. But in contrast, it will demand a huge quantity of other kinds of natural resources being some of them even scarcer than oil. Some of these resources will be necessary to manufacture the following components: batteries (Co, Ni, Mn or Li); LEDs for lighting (Ga, Ge, Y); permanent magnets for motors (Nd, Dy, Pr); catalytic converters (Pt, Pd, Zr); electronic units (Au, Ag, Sn, Ta, Yb), different kinds of sensors (Ce, Tb, Se, La), infotainment screens (In); automotive high performance steel or aluminum alloys (Nb, Mo, Cr, Ti, V, Sc, W) or injectors (Tb). Unfortunately these resources are finite and some of them are very scarce being even considered as critical for the European Commission and other institutions from several perspectives such as vulnerability, economic importance, supply, or ecological risks.
One of the solutions to improve resource efficiency in vehicles is to recycle these valuable metals. Nevertheless, there are two main problems around the recycling situation. On one hand, recycling rates are not growing up as faster as metal demand. On the other hand, current recycling policies define targets based on mass weight approaches, and even if they are ambitious, they fail in enhancing the recycling of minor but critical metals. The legislation compliance is achieved by means of applying mechanical separation techniques. These processes are effective to recycle those metals with the highest contribution in the vehicle weight (steel, aluminum and copper) but they are not effective for the recovery of minor metals like those that are scarce and/or critical. Consequently, minor metals end downcycled during steel or aluminum smelting or in the worst case they finish dispersed in landfills.
This Thesis is presented with the main aim to improve the resource efficiency in the vehicle manufacturing sector. To accomplish with this aim, a novel method for measuring the resource efficiency and to identify possible shortages in the supply of metals is presented.
The resource efficiency is analyzed through the second law of Thermodynamics through the concept of thermodynamic rarity. This method takes into account the quality of mineral commodities as a function of their relative abundance in Nature and the energy intensity required to extract and process them. The application of the thermodynamic approach allows not only to recognize the physical value of materials with a low weight contribution but also to identify those components that use them.
As it has been mentioned before this Thesis also assesses possible metal shortages. This activity is made by means of an own method which combines geological data (reserves and resources), annual capacity production, annual expected demand, cumulative expected demand to 2050, recycling rates evolutions and future resource demand of other technologies.
The methodology is applied to different types of vehicles (ICEV , PHEV and BEV ) and it has been useful to achieve the following main results: (1) From a thermodynamic point of view an electric vehicle demands 2.2 times more quality resources than a combustion one; (2) 31 critical components were identified in a conventional vehicle from the perspective of the materials used to manufacture them; (3) Eco-design recommendations for these components have been defined. These recommendations are based on: reducing the demand of scarce metals and to increase both the recyclability and the reusability; (4) In current End of Life Vehicle (ELV) processes 27 % of the mineral capital (measured in rarity terms) is not functionally recycled; (5) Recommendations to reduce these losses have been proposed; (6) A strategic metal ranking for the automobile sector has been produced, being the top 10 most strategic metals the following: Ni, Li, Tb, Co, Dy, Sb, Nd, Pt, Au and Ag.
The contributions of this Thesis are valuable to improve the sustainability of the vehicle manufacturing sector from the raw materials point of view. These contributions are mainly valuable for the following stakeholders: (1) Designers because it helps them to apply eco-design proposals from a raw materials point of view; (2) Policy makers because it evidences the weakness of mass based approach recycling policies and it proposes an alternative method that takes into considerations not only quantity but also quality; (3) Company’s executives because it confronts them with the metal dependency and vulnerability of technology and it helps them to plan with enough time R+D+i lines based on resource efficiency.
