Life Cycle Assessment of Environmental Systems: A Review of Methodologies, Applications, and Future Directions

Life Cycle Assessment has become central to evaluating environmental systems. With growing climate and resource pressures, LCA is now applied beyond products to energy, water, waste, and urban systems, yet methodological variability affects consistency and policy relevance. This review aimed at examining LCA methodologies, mapping current applications to environmental systems, and identifying challenges and future directions for improved decision support. Findings from this study revealed that methodological advances include wider adoption of consequential and hybrid LCA, dynamic modelling, regionalized inventories, and uncertainty analysis. Database harmonisation and open LCA platforms have improved data accessibility, though foreground data gaps persist. In impact assessment, there is progress toward ecosystem services, toxicity, and planetary boundary metrics. Application-wise, LCA is extensively used for renewable energy systems, carbon capture, water and wastewater treatment, agriculture, and built environments to inform eco-design and policy instruments like EPDs and carbon labels. Case studies show LCA supports technology comparison and circular economy strategies. However, inconsistencies in system boundaries, allocation, and temporal considerations limit comparability. Emerging integrations with AI, process simulation, and digital twins enable near real-time assessment, while prospective LCA is gaining traction for novel technologies. Standardisation and transparency remain key barriers. LCA is evolving from static product assessment to a dynamic systems tool for environmental decision-making. Future progress depends on methodological harmonisation, higher quality and open data, and integration with AI and policy frameworks. Strengthening these areas will enhance LCA’s role in guiding sustainable design, circularity, and net-zero transitions across environmental systems.