Alicia Valero

The automotive sector is the third-largest consumer of plastics in Europe, after packaging and construction, and its demand is expected to grow. Plastic recycling at the end of vehicle life remains low, with 80% of plastics ending up in energy recovery or landfills. Three vehicle models (SEAT Ibiza Gen. IV and SEAT Leon Gen. II and III) with two trim versions (Reference and Formula Racing) were examined to identify the most critical plastic components from an exergy perspective. Ecodesign measures were defined by considering both the disassemblability of vehicle components and their recyclability potential as key criteria to evaluate end-of-life recovery pathways and guide material and design optimization strategies. The proposed methodology classified the measures into three types: (1) substitution of high-exergy plastics with lower-impact alternatives; (2) use of recycled plastics instead of primary materials, with substitution rates depending on the material; and (3) reuse of components in new models, evaluated by disassemblability and end-of-life condition. Results show that Type 1 measures achieved savings up to 70 MJ, mainly in the floor covering and engine compartment insulator, while Type 2 measures provided larger reductions, up to 1.7 GJ, mainly in bumpers and carpets. Type 3 measures showed reuse potential for paddings and insulators but faced limitations in carpets and dashboards. Findings highlight the importance of material selection and implementing disassembly and recycling strategies to reduce the exergy of vehicle plastics.

The momentum of the Fourth Industrial Revolution is driving increased demand for certain specific metals. These include copper, silver, gold, and platinum group metals (PGMs), which have important applications in renewable energies, green hydrogen, and electronic products. However, the continuous extraction of these metals is leading to a rapid decline in their ore grades and, consequently, increasing the environmental impact of extraction. Hence, obtaining metals from secondary sources, such as waste electrical and electronic equipment (WEEE), has become imperative for both environmental sustainability and ensuring their availability. To evaluate the sustainability of the process, this paper proposes using an exergy approach, which enables appropriate allocation among co-products, as well as the assessment of exergy losses and the use of non-renewable resources. As a case study, this paper analyzes the recycling process of waste printed circuit boards (PCBs) by disaggregating the exergy cost into renewable and non-renewable sources, employing different exergy-based cost allocation methods for the mentioned metals. It further considers the complete life cycle of metals using the Circular Thermoeconomics methodology. The results show that, when considering the entire life cycle, between 47% and 53% of the non-renewable exergy is destroyed during recycling. Therefore, delaying recycling as much as possible would be the most desirable option for minimizing the use of non-renewable resources.

The impulse of the Fourth Industrial Revolution is triggering the demand for few specific metals. These include copper, silver, gold, and platinum group metals (PGMs), with important applications in renewable energies, green hydrogen, and electronic products. However, the continuous extraction of these metals is leading to a rapid decline in their ore grades and, consequently, increasing the environmental impact of extraction. Hence, obtaining metals from secondary sources, such as waste electrical and electronic equipment (WEEE), becomes imperative for both environmental sustainability and ensuring availability. This recovery entails few problems such as allocation due to the simultaneous production of several metals, the use of non-renewable resources, and the exergy destruction during the life cycle of the metals. Therefore, this work analyses the waste printed circuit boards (PCBs) recycling process by proposing different exergy-based cost allocations for the mentioned metals, disaggregating the exergy cost into non-renewable and renewable, and considering the complete life cycle of metals with the Circular Thermoeconomics methodology. The results show a significant saving of non-renewable energy by using renewable energies in primary extraction (67-87%), recycling (97.6-98.5%), and renewable energies in recycling (98.7%, 99.0%), compared to conventional primary extraction. However, when considering the entire life cycle, between 47% and 53% of the non-renewable exergy is destroyed during recycling. Therefore, delaying recycling as much as possible would be the most desirable option for maximizing the use of non-renewable resources, which nature cannot replace in a short time.

A conventional vehicle requires more than 50 different metals in its manufacturing, most of which are critical. Given this circumstance, enhancing sustainability from a raw materials perspective requires improvements in the disassemblability of car parts. This enhancement aims to yield metal-rich fractions, enabling the application of effective recycling processes for the recovery of critical metals. This helps avoid the downcycling that occurs in conventional shredding processes. The present study was undertaken to analyze the challenges associated with disassembling components of significant value due to their metal content. The methodology comprises two distinct main stages: an identification of critical car parts and an assessment of disassemblability. The selection of car parts was determined by the criticality of each one through the thermodynamic rarity indicator. Disassemblability was studied experimentally, encompassing three different levels. This classification defines the stages from extracting parts from the vehicle and obtaining recycling fractions in their purest form: ferrous metals, aluminum, non-ferrous metals excluding aluminum, and plastics. This methodology was implemented on two vehicles manufactured by SEAT: SEAT Leon models II and III. As a result, not only was disassemblability information about these car parts collected, but several ecodesign recommendations were also identified as valuable guidance for future designs, specifically aimed at enhancing metals’ recyclability. In conclusion, it must be acknowledged that contemporary vehicle design often prioritizes cost-effective manufacturing processes. However, this approach may compromise the disassemblability and recyclability of the product. The ongoing transition to electric vehicles necessitates a re-evaluation of design principles, particularly from the perspective of the circular economy.

Annually we consume far more natural resources than the earth can regenerate in one year. Some of those natural resources are and will be extensively used to manufacture the solutions intended to slow down climate change and/or to mitigate its effects. Demand is constantly rising over time. If no additional measures are taken, this could lead to bottlenecks in supply in specific sectors that are highly dependent upon critical raw materials. The so-called circular economy can partly offset such bottlenecks. Yet, as we highlight in this chapter, thermodynamic limits and our technological limitations prevent materials from being fully recovered. Hence, strict circularity does not exist. Instead, the “spiral economy” concept should be promoted, aimed at recirculating materials not only one time but many times, highlighting also the importance of lengthening the lifespan of all products and minimizing losses.

Even if there are multiple definitions, depending on the factors and boundaries considered, there is a certain consensus to label as critical those materials whose availability, or rather the lack of it, could put the economy at risk. This means that any material can become critical if the demand exceeds supply, an issue that is becoming more evident in recent times. Some examples of critical materials are gallium, niobium, rare earths elements or cobalt, which normally are part of a larger list of elements of the periodic table, a list that keeps growing over time.

Light-duty vehicles are increasingly incorporating plastic materials to reduce production costs and achieve lightweight designs. On average, a conventional car utilizes over 200 kg of plastic, comprising more than 23 different types, which often present challenges for recycling due to their incompatibility. Consequently, the focus on plastic recycling in end-of-life vehicles has intensified. This study aims to analyze critical car parts based on the plastics used, employing a novel thermodynamic approach that examines the embodied exergy (EE) of different plastics. Six vehicles from various segments, years, and equipment levels were assessed to understand their plastic compositions. The findings reveal that, on average, a vehicle contains 222 kg of plastic, accounting for 17.7% of its total weight. Among these plastics, 47.5% (105 kg) are utilized in car parts weighing over 1 kg, with plastics comprising over 80% of the part’s weight. The identified critical car parts include the front door trim panel, front and rear covers, fuel tank, floor covering, front lighting, dashboard, rear door trim panel, plastic front end, backrest pad, door trim panel pocket, plastic foam rear seat, rear lighting, window guide, molded headliner, bulkhead sound insulation, foam seat part, and wheel trim. Regarding their contribution to EE, the plastics with the highest shares are polypropylene—PP (24.5%), polypropylene and ethylene blends—E/P (20.3%), and polyurethane- PU (15.3%). Understanding the criticality of these car parts and their associated plastics enables targeted efforts in design, material selection, and end-of-life management to enhance recycling and promote circularity within the automotive industry.

The path toward energy transition requires many metals, some of which are scarce in nature or their supply is controlled by a few countries. The European and Spanish situations are particularly vulnerable because of the scarcity of crucial geological mineral resources, especially those known as critical. In this context, the recovery of metals from waste electric and electronic equipment (WEEE) presents an important opportunity to partly alleviate this situation because this region produces most of the WEEE per capita. In this study, 43 different categories of EEE placed in the Spanish market between 2016 and 2021 were assessed, considering the composition of up to 57 elements, with 34 being critical. The results show the great opportunities for urban mining: 1.4 million tons of metals valued at USD 2.43 billion, representing 80% of the mass and 25% of the price of the primary extraction in Spain during that period. In addition, 20,000 tons corresponded to critical metals. However, the short life of EEE and the low traceability and low recovery of metals, especially critical and precious (94% and 87% of their values are lost, respectively), make it necessary to overcome major challenges to develop a new industry capable of moving toward a deeper circular economy.