Life cycle assessment of pig iron production from bauxite residue: A European case study

Large volumes of bauxite residue are generated when alumina is leached from bauxite ore, within 2-3 metric tons of bauxite residue per metric ton final aluminum. The large volumes make bauxite residue an interesting source for secondary materials, for instance iron. This paper assesses environmental impacts associated with extraction of pig iron from bauxite residue in Europe. The life cycle assessment is based on thermodynamic process simulation and compares pig iron from bauxite residue with conventional pig iron production. The results indicate that the iron extraction reduces impacts on mineral scarcity and offers an overall lower waste volume. However, it also increases the energy use and thereby the life cycle impacts associated with energy production. The bauxite residue process is operated in an electric arc furnace. Decarbonizing the electricity supply, or placing the process in primarily renewable electricity markets, changes the relative competitiveness of pig iron from bauxite residue, to a level where it offers lower endpoint impacts to ecosystems, human health, and resources, as well as improvements in policy-relevant midpoint impacts such as climate change. Comparing several bauxite residue mineralogies, the results show significant variation in the environmental performance between typical bauxite residues, yet a larger difference is observed when comparing with conventional pig iron production than among the bauxite residues.

Automated summary

This paper assesses the environmental impacts of extracting pig iron from bauxite residue, finding that while it reduces mineral scarcity and waste volume, it also increases energy use and overall life cycle impacts. However, decarbonizing the electricity supply improves the environmental performance of pig iron from bauxite residue, including impacts on ecosystems, human health, and climate change.