Comparison between Different Hybrid Life Cycle Assessment Methodologies: A Review and Case Study of Biomass-based p‑Xylene Production

Two common life cycle assessment (LCA) methods are process LCA and economic input–output LCA, which suffer from truncation error and aggregation error, respectively. Many hybridization techniques are developed to improve the accuracy of analysis by combining both methods. This work aims to review different hybrid LCA methodologies under various data availabilities through a case study of two biomass-based p-xylene production technologies using concentrated acid (CA) and molten salt hydrate (MSH) hydrolysis. The MSH process without selling electricity to the grid has a lower global warming potential than the CA process when evaluated by process LCA, tiered hybrid LCA, and integrated hybrid LCA after binary correction for double counting. With prior knowledge on LCA databases or assumptions on economic activities that are irrelevant to the production, double counting could be further eliminated, and the MSH process would behave similarly or even worse than the CA process.