Uncertainty analysis in life-cycle assessment of early-stage processes and products: a case study in dialkyl-imidazolium ionic liquids

This paper presents a methodology for combining foreground and background uncertainty in the life-cycle assessment (LCA) of processes and products at a low technology-readiness level. We compare the LCA of two ionic liquids, 1-butyl-3-methyl-imidazoliumtetrafluoroborate [bmim][BF4] and 1-butyl-3-methyl-imidazolium hexafluorophosphate [bmim][PF6]. The nominal scenario predicts that [bmim][BF4] generates lower end-point environmental impacts than [bmim][PF6]. However, the uncertainty ranges around these nominal predictions overlap significantly, with [bmim][BF4] causing higher impacts than those of [bmim][PF6] in up to 30% of the uncertainty scenarios. On top of this, accounting for uncertainty in the foreground data more than doubles the estimated impact ranges in several damage categories. This case study, therefore, demonstrates the need for combining foreground and background data uncertainty for more reliable life-cycle assessments.