Life Cycle Assessment of Sustainable Materials: A Comprehensive Analysis of Methodological Asymmetries and Environmental Trade-Offs

Comparative Life Cycle Assessments (LCAs) of bio-based materials are highly influenced by methodological choices, so the term “bio-based” does not necessarily imply a low environmental impact. This review analyzes over 50 peer-reviewed LCAs (2010–2024) to quantify how four methodological pillars—(i) attributional versus consequential modeling, (ii) timing and storage of biogenic carbon, (iii) Direct Land-Use Change (LUC) and Indirect Land-Use Change (ILUC), and (iv) allocation in multifunctional systems—drive variability across long-life construction and short-life packaging/composites; adding regionalized perspectives (e.g., water scarcity according to the AWARE initiative, and relevant inventories for the MENA region) and ex-ante LCA guidance aligned with technology readiness levels. Methods included systematic selection from Web of Science/Scopus databases, standardized functional units, system boundaries, impact methods (ReCiPe/EF/TRACI/AWARE), biogenic carbon conventions (GWP100, dynamic/GWPbio), LUC/ILUC handling, allocation rules, and end-of-life scenarios, followed by qualitative meta-synthesis. Results show ~85% of studies used attributional approaches; consequential models typically report higher climate impacts when ILUC is included. In the building applications, bio-based alternatives—particularly wood—reduced cradle-to-critical-state global warming potential (GWP) by 30–70%; a “negative GWP” only emerged when storage balances or dynamic characterization were applied. For bioplastics, climate benefits are context-dependent and can disappear once ILUC and agricultural inputs are considered; acidification and eutrophication frequently increase. We conclude that environmental performance is subject to methodological choices rather than bio-based origin; systematic trade-offs persist between reducing GWP, increasing eutrophication/acidification, and increasing pressure on water/biodiversity.