Are Polymeric Membranes Truly Sustainable? Life Cycle Assessment Studies of Polymeric Membranes in Post-Combustion CO2 Capture: A Systematic Review

capture (PCC), yet their life cycle environmental performance remains uncertain. This review synthesizes 21 life cycle assessment (LCA) studies of polymeric membrane-based PCC systems to examine methodological choices, quantify environmental trade-offs, and identify research gaps. Google Scholar, Web of Science, ScienceDirect, and MDPI were searched up to January 2026. Methodological quality and risk of bias were assessed against a 10-criteria framework derived from ISO 14044. Results indicate widely varying system boundaries and functional units, with only four studies performing formal uncertainty analysis. Within individual study contexts, polymeric membrane gas separation systems can reduce global warming potential (GWP) by up to 89% compared to no-capture plants, though other impacts, like ozone depletion potential, increase by up to 780%. Compared to amine-based absorption, membranes showed superior performance, with reductions up to 26% in GWP and 98% in other categories. In some cases, large relative reductions are driven by scenario-specific baselines and should be interpreted with caution. Outcomes were most sensitive to background energy mixes and raw material demand. The absence of commercial-scale data highlights the need for harmonized frameworks and standardized functional units. Future research should prioritize membrane material selection, renewable energy integration, and coordinated policy-industry collaboration.