From aluminium to composites: A comparative social life cycle assessment of automotive lightweight components
Suzana Ostojic, Marzia Traverso
Abstract
This study applies a Social Life Cycle Assessment (S-LCA) to compare the social sustainability of conventional aluminum cross-car beams (CCBs) with composite alternatives in which approximately 50 % of the aluminum is replaced by a glass fiber-reinforced polymer (GFRP). A two-step methodological framework, aligned with UNEP S-LCA guidelines and ISO 14075, was implemented: first, a social risk assessment identified very high risk (VHR) subcategories affecting specific stakeholder categories; second, a social footprint analysis quantified potential impacts through the Social Hotspot Index (SHI), which integrates labor intensity with social risk levels. Workers and local communities emerged as the only stakeholder categories associated with VHR subcategories in both CCB supply chains. The social footprint analysis quantified significant hotspots in aluminum-related processes, particularly bauxite extraction, aluminum manufacturing, and sheet production. Substituting aluminum with GFRP composites reduced cumulative SHI values by 24–36 % across VHR subcategories, with residual aluminum processes remaining major contributors to the social footprint of the composite variant. While the method is broadly applicable, the findings are case-specific - reflecting, e.g., a cradle-to-gate system boundary - and are not generalizable to the entire automotive sector. As the assessment partially relies on secondary supply chain data and proxy unit processes from established S-LCA databases, the results are not intended for direct supply-chain decision-making. However, the study informs the prioritization of stakeholders, subcategories, and unit processes for future CCB S-LCAs as technical development progresses and primary data becomes available. Overall, it highlights the potential of composites to reduce social impacts in automotive lightweight products. • First S-LCA of aluminum and composite automotive cross-car beam components. • Case study identifies lower quantities of social risks for composite cross-car beams. • Workers and local communities are most impacted in both material supply chains. • Composites reduce potential social impacts by 24–36 % compared to aluminum beams. • Social hotspots include bauxite mining, aluminum production, and sheet manufacturing.