Life cycle assessment of livestock production: A systematic review of methodological advances, harmonization challenges, and future directions

Food production systems are major contributors to global environmental impacts, and life cycle assessment (LCA) has become a key methodology for quantifying environmental burdens across product life cycles. This systematic review examines 93 peer-reviewed studies applying LCA to livestock meat production, aiming to assess methodological harmonization and comparability while identifying emerging issues and research gaps. The review reveals substantial methodological inconsistencies, particularly regarding allocation methods, system boundary definitions, functional units, and emission modelling, which limit comparability across studies. Ruminant systems generally show higher environmental impacts than monogastric systems, although reported values vary widely depending on modelling assumptions, data sources, and regional contexts. The frequent use of generic or outdated inventory data further increases uncertainty and reduces representativeness. In addition, biodiversity, ecosystem services, soil carbon dynamics, land-use change, and other site-specific environmental aspects remain poorly integrated into livestock LCA studies. Overall, variability in methodological choices reduces the robustness and policy relevance of LCA outcomes for livestock meat systems. Future research should prioritize harmonized methodological frameworks, region-specific and dynamic models, improved data transparency, and the integration of biodiversity and ecosystem-service-related indicators to enhance the reliability and decision-making value of livestock LCA.