Circular economy and life cycle assessment of alumina production: Simulation-based comparison of Pedersen and Bayer processes

The excessive production of bauxite residue (red mud) in the Bayer process is one of the major challenges amongst alumina producers. The Pedersen process is known as a combination of smelting reduction of bauxite and leaching treatment of the produced slag for alumina production, and the process also produces an inert bauxite residue (grey mud), which is more suitable for further processing compared to the red mud. This paper describes the life cycle assessment for two alumina production processes, the current commercialized Bayer process and the alternative Pedersen process, based on the complete mass and energy balance simulation. Process simulation and environmental software are applied to quantify the metallurgical processes and their related environmental effects. By assuming the same treatments for the bauxite residues, it is found that, with the production of pig iron, the Pedersen process shows the best performance in mineral resource scarcity but requires a higher energy demand and generates twice the amount of bauxite residue compared to the Bayer process. The final, relative performance in climate change impact depends on the carbon intensity of energy and the bauxite ore composition.