Ex ante life cycle assessment of bauxite residue vitrification technology

Abstract

Purpose: The increasing need for novel technologies with reduced environmental impacts is driving a need for early assessment of their environmental performance, both for evaluating their potentials and supporting early-stage technology optimization. Here, we quantify the environmental performance of an emerging vitrification technology for recycling bauxite residue into a supplementary cementitious material using ex ante life cycle assessment (LCA). Methods: We determine the influence of scale (i.e., laboratory, pilot, and industrial) and upscaling approach (i.e., process modeling, regression analysis, and proxy technology) on the environmental performance of this emerging vitrification technology. We produced industrial-scale LCA results at year 2050 by incorporating background changes defined using electricity mixes consistent with shared socioeconomic pathway 2 (SSP2) baseline, representative climate pathway 1.9 (RCP1.9), and SSP2 RCP2.6 scenarios, which are consistent with ~ 1.5–4.2 °C warming by 2100 relative to 1980. Results and discussion: The results show significant reductions in environmental impacts from technology upscaling, of > 94% from laboratory to industrial scale, and ~ 83% from pilot to industrial scale. Upscaling resulted in low to moderate variances across most impact categories. Higher energy demands and fossil fuel-based sources in proxy scenarios led to significant variances. The results indicate that regression analysis and proxy technology can be comparable to process modeling if appropriate proxy technology is used, for the vitrification technology studied here. Incorporating background changes using a low carbon electricity scenario (SSP2 RCP1.9, consistent with ~ 1.5 °C warming by 2100 relative to 1980) resulted in reductions in many impact category indicators (CO2-eq., kg oil eq., etc.) up to ~ 94% by 2050. However, trade-offs were observed in many impact categories such as agricultural land occupation (12% increase) and material depletion (30% increase), resulting from increased biomass and wind electricity generation. Conclusions: This study provides a structured framework for scaling bauxite residue (BR) vitrification from laboratory to industrial scale, demonstrating how different upscaling approaches and key parameters influence its environmental performance. By identifying trade-offs and environmental hotspots, it supports early-stage optimization and technical decision-making. The study highlights the importance of integrating future background scenarios such as electricity grid decarbonization into ex ante LCA studies of emerging technologies at future industrial scales. In BR vitrification, these background changes had a major influence on the projected environmental impacts. Together, these insights provide practical guidance for early-stage improvement of BR vitrification technology and are relevant for other emerging technologies in foundation industries (e.g., cement, metals, ceramics).