Supply is the quantity of a product that is made available by producers at a particular price level or set of market conditions within a defined geographical area and time period. In Life Cycle Assessment, supply represents the total provision of products from all producing activities that make that product available to consumers and other activities requiring it as an input.
Within LCA system modelling, supply plays a crucial role in understanding product flows and market dynamics. The concept extends beyond simple economic availability to encompass the full set of activities that provide products within a product system. Supply data forms the foundation for constructing supply-use tables, which are essential tools for input-output based LCA approaches and for understanding the structure of economic activities and their environmental implications.
The supply of a product in a given geographical area includes both domestic production and imports. This combined supply is sometimes referred to as the supply mix, distinguishing it from the production mix which considers only domestically produced quantities. Understanding the complete supply picture is particularly important in consequential LCA modelling, where changes in demand must be matched against available supply and the constraints on expanding production capacity.
In LCA databases and modelling frameworks, supply information helps determine which activities contribute to meeting demand for specific products. Market activities in LCA explicitly represent this supply function, aggregating product outputs from multiple supplying activities and distributing them to consuming activities based on factors such as geographical proximity, market share, and technological characteristics.
The relationship between supply and demand is fundamental to understanding how product systems respond to changes. When demand for a product increases, the supply response depends on factors including production capacity, resource availability, and economic constraints. These dynamics are particularly relevant in consequential LCA, where practitioners must identify which suppliers will respond to marginal changes in demand and what environmental consequences follow from those supply adjustments.
