Life Cycle Assessment: Conceptual Foundations, ISO Standards, and Methodological Evolution

Life Cycle Assessment (LCA) has become one of the most rigorous, internationally standardised, and widely adopted environmental analysis tools available to researchers, policymakers, and industry practitioners. This paper provides a comprehensive and critically oriented conceptual foundation for the methodology. Drawing on the ISO 14040/14044 normative framework, the foundational scholarship of Jolliet et al. (2016), and complementary literature in environmental management and sustainability science, the paper traces the historical evolution of LCA from early energy-balance studies of the 1970s through the global flagship projects of the UNEP-SETAC Life Cycle Initiative in the present decade. The four canonical LCA phases — goal and scope definition, inventory analysis (LCI), impact assessment (LCIA), and interpretation — are introduced, defined, and their current levels of methodological maturity critically assessed. Crucially, the paper situates LCA within a comparative framework alongside five complementary environmental assessment tools: Substance Flow Analysis (SFA), Environmental Impact Assessment (EIA), Risk Assessment (RA), Material Flow Analysis (MFA), and the Carbon Footprint (CF). The distinctive characteristics of LCA — systems-wide cradle-to-grave scope, multi-issue impact coverage, and function-based comparative orientation — are identified and their significance for sustainable decision-making elaborated. The paper then examines the methodological evolution of LCA from a technical instrument into a strategic governance framework, including its integration with Environmental Product Declarations (EPDs), green building certification, and circular economy policy. Practical applications across the food, construction, and energy sectors are surveyed to demonstrate LCA's cross-sectoral reach. The paper concludes with a structured roadmap for the seven subsequent papers in the series and a how-to-cite block for academic reuse.