Using Life Cycle Thinking to Assess the Sustainability Benefits of Complex Valorization Pathways for Bauxite Residue

Abstract

Bauxite residue, the main waste product of alumina production, is a potentially valuable secondary resource. The MSCA-ETN REDMUD project aims to develop environmentally friendly technologies to realize this value, by extracting valuable metals (aluminium, iron, titanium, scandium, rare-earth elements) or utilizing it in construction applications. Simply utilizing a waste product as an input is not, however, sufficient to claim that a process is environmentally friendly; the processes developed must be demonstrably better for the environment, from a life cycle perspective, than business as usual. The earlier in the research and development process that environmental information can be taken into account, the more impact it can have on decision-making. In this study we demonstrate that Life Cycle Thinking approaches can provide actionable environmental information at an early stage in the research process, and that in doing so it can help steer early stage technology development towards overall improved industry environmental performance. Knowledge of the potential environmental benefit from displacing different materials can help identify primary or additional targets, for example the use of metal extraction residues for construction materials. A high-level 'red flags' assessment of the relative environmental impact of inputs to valorization processes and the products they displace can be used to identify problematic inputs and processes in the absence of quantitative details. Finally, once preliminary quantitative data are available for a process, streamlined Life Cycle Assessment can be used to calculate the environmental balance of a process, and identify specific hotspots of environmental impact.

The sustainable materials roadmap

“…It is however also possible to use life cycle thinking approaches to do preliminary assessments in early stages. These can provide actionable environmental information in the research process and in doing so it can help steer technology development towards overall improved environmental performance [321]. Such methods can include semi-quantitative 'red-flag' assessments, highlighting areas of concern, to guide further research as well as streamlined assessments, possibly using upscaling methods as soon as quantitative data becomes available.…”

Application of LCA modelling in integrated waste management

“…Other examples can be found in e.g. Joyce and Björklund (2019). Eutrophication, generic kg PO 4 -eq 6.4 x10 -5 1.1x10 0 1.2x10 -1 6.3x10 -2 Depletion of abiotic resources kg antimony eq 3.3x10 -4 5.6x10 0 6.0x10 -1 3.1x10 -1 Acidification, generic kg SO 2 -eq 2.2x10 -4 2.7x10 0 3.0x10 -1 1.6x10 -1 Photochemical oxidation, high NO x kg ethylene-eq 2.1x10 -5 1.6x10 -1 1.7x10 -2 8.9x10 -3 Climate change, 100a kg CO 2 -eq 1.0x10 -1 3.5x10 2 4.0x10 2 2.2x10 1 Terrestrial ecotoxicity kg 1,4-DCB-eq 1.7x10 -6 3.6x10 -2 3.8x10 -3 2.0x10 -3 Freshwater aquatic ecotoxicity kg 1,4-DCB-eq 4.1x10 -1 2.6x10 2 2.7x10 1 1.4x10 1 Stratospheric ozone depletion kg CFC-11-eq 7.3x10 -9 7.1x10 -5 7.5x10 -6 3.9x10 -6 Human toxicity, infinite kg 1,4-DCB-eq 7.3x10 -2 1.0x10 3 1.1x10 2 5.4x10 1…”

Guiding Future Research on the Valorisation of Shredder Fine Residues: A Review of Four Decades of Research

“…Furthermore, associated sustainability concerns such as environmental impacts, costs of the involved processes, and income/savings from valorised products could simultaneously be considered as part of process development. Examples are the identification of particularly significant environmental impacts (hotspots) (Joyce et al, 2018), and key sources (material and energy inputs) of such impacts and potential substitutes (Joyce and Björklund, 2019).…”