Direct Melting of Pre-consumer/Prompt Scrap at Foundries as a LowCO2 Alternative for SecondaryAluminium Delivery : Optimising Scrap Utilisation and Carbon Footprint Calculations inEuropean Aluminium Supply Chains

Sammanfattning

The aluminium sector plays a crucial role in global material demand and the transition toward low-carbon andcircular systems, It also remains a major source of global energy use and greenhouse gas (GHG) emissions,particularly in primary production based on electrolysis. As global aluminium demand continues to grow, primaryproduction will likely remain dominant for the foreseeable future, making improved recycling and secondaryproduction increasing crucial. However, while secondary aluminium has a lower environmental burden, currentsystems still show inefficiencies. In this context, direct melting of pre-consumer/ prompt aluminium scrap at afoundry level offers a promising alternative, but its environmental performance is yet to be adequately analysedin life cycle assessment (LCA) studies. This study applies a cradle-to-gate LCA to evaluate carbon footprint across direct foundry-level melting of preconsumer/ prompt scrap as an alternative to conventional centralised secondary aluminium production in aSwedish context within Europe. The conventional system is modelled as a multistage process involving scrapcollection, remelting into ingots, and subsequent casting, while the alternative system considers scrap directmelting at foundries. The analysis includes environmental impacts from energy demand, transport requirements,metal losses, alloy and primary aluminium additions, and variations in scrap quality across pre-consumer/promptand post-consumer/obsolete streams, with a functional unit of 1 kg of liquid aluminium available at the foundryfor casting. Environmental impacts are reported as kg CO₂e per kg of liquid aluminium. Sensitivity tomethodological choices is examined through application of both the cut-off and co-product allocation approaches. Results show that, under the cut-off approch, direct melting provides clear environmental benefits of around 48%in carbon footprint reduction, due to avoided remelting, reduced transport, and lower metal losses. However, thesebenefits are reduced by increasing carbon footprint around 25% under co-product allocation, where primaryproduction burdens are partly shared within the system. In both approaches, metal losses remain the dominantcontributor to the carbon footprint across the recycling processes. In summary, the study shows that thecomparative environmental performance of direct melting strategies is highly sensitive to LCA methodologicalframing, particularly allocation choices. It also provides new evidence on the role of scrap stream characteristicsand system configuration in aluminium recycling assessments, while also highlighting the implications ofmethodological variability for interpreting environmental benefits in secondary aluminium systems.