Life cycle assessment is a method for quantifying the environmental impacts of products, processes or services from raw material extraction to end of life. It follows four main phases: goal and scope definition, life cycle inventory, impact assessment and interpretation.

In the goal and scope phase, practitioners define the purpose of the study, the functional unit that describes what is being assessed and the system boundaries that determine which processes are included. This step influences all subsequent choices and the relevance of the results.

The life cycle inventory compiles all inputs and outputs associated with the system. This includes energy use, raw materials, emissions to air, water and soil and waste flows. Data quality and representativeness are critical, so foreground data from the specific system are often combined with background data from databases.

The impact assessment phase translates inventory flows into environmental impact categories. Common categories include climate change, acidification, eutrophication, photochemical ozone formation, resource depletion and various human and ecotoxicity measures. Characterization models and factors quantify contributions of each flow to each impact.

Interpretation brings together results, evaluates uncertainties and identifies hotspots where improvements are most effective. Sensitivity and scenario analyses help test the robustness of conclusions.

Research in this field addresses methodological choices such as allocation of burdens in multifunctional systems, treatment of recycling, temporal and spatial differentiation of impacts and integration with economic and social assessment. Applications span energy systems, agriculture, waste management, construction materials and consumer products, supporting eco design, policy making and corporate sustainability strategies. Continuous work on data quality, impact modelling and transparency aims to make life cycle assessment more reliable and practically useful.