The life cycle inventory analysis result (LCI result) comprises the Elementary exchanges of a Product system. This result represents the comprehensive catalogue of all flows that cross the system boundary between the product system and its surrounding environment throughout the entire life cycle of the product being studied.
According to ISO 14040 clause 3.3, Life Cycle Inventory analysis (LCI) is defined as the phase of life cycle assessment involving the compilation and quantification of inputs and outputs for a product throughout its life cycle. The LCI result is the outcome of this analytical phase.
Elementary exchanges are the fundamental building blocks of an LCI result. These represent exchanges between activities within the product system and the natural, social or economic environment. Examples include unprocessed inputs extracted from nature (such as mineral resources, water, or land use), emissions to air, water and soil, physical impacts on the environment, and working hours under specified conditions. Importantly, these are flows that have not undergone previous human transformation when entering the system, or will not undergo subsequent human transformation when leaving the system.
The LCI result serves a critical function within the broader LCA framework. As ISO 14040 states, it catalogues the flows crossing the system boundary and provides the starting point for life cycle impact assessment. This means the LCI result forms the essential foundation upon which environmental impact assessment is built. The elementary exchanges documented in the LCI result are subsequently processed through characterisation models during the Life Cycle Impact Assessment (LCIA) phase to evaluate their potential environmental impacts.
In essence, whilst the LCI result itself does not express environmental impacts, it provides the quantified inventory of environmental interventions that enables impact assessment to proceed.
