Environmental impacts of supercritical fluids processes: A critical review of life cycle assessment studies
Résumé
The application of supercritical fluids (SCF) in industrial and research processes has gained attention in recent years for their unique properties and potential environmental benefits. Frequently described as "green solvents", SCF can reduce of replace the use of conventional organic solvents. However, broader adoption requires a clear understanding of their full life cycle environmental impacts. Life cycle assessment (LCA) has been widely used to evaluate the environmental performance of SCF technologies.This study critically reviews 70 LCA studies of SCF processes across various applications through the four phases of LCA: goal and scope definition, life cycle inventory, life cycle impact assessment, and interpretation to identify methodological gaps and trends in energy use, solvent consumption, and environmental impacts. Despite variability in modelling approaches, process-level trends emerge: for gasification, global warming results range from -0.2 to 5 kg CO2eq.kg$_{input}^{-1}$; for extraction from 0.2 to 153 kg CO2eq.kg$_{input}^{-1}$ depending on feed and scale. Contribution analyses highlight that energy is the main hotspot, especially in supercritical water gasification and transesterification, even though yielding higher-quality output and lower solvent consumption. Benchmarking results are mixed: 27 studies reporting lower environmental impacts for SCF processes, while 18 studies report higher impacts, especially in extraction applications. Sensitivity analyses highlight the influence of electricity mix, feed concentration, and solvent recycling on LCA outcomes. This review provides targeted recommendations to enhance consistency and accuracy in future LCA studies. By synthesizing current findings, it supports the development of more sustainable SCF technologies from early stage to support their broader adoption.
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