Upstream refers to processes and activities occurring backwards in the life cycle relative to the activity being studied. This means tracing the chain of production towards raw material extraction and the initial production of products. The term describes the directional flow of material and energy inputs as they move through successive stages of transformation before reaching the focal activity under investigation.
In Life Cycle Assessment, understanding the upstream portion of a product system is essential for capturing the full environmental burden associated with a product. Upstream activities include the extraction of raw materials, processing of these materials into intermediate products, manufacturing of components, and transportation of materials and components to the facility where the studied activity takes place.
When conducting an LCA, practitioners must identify and quantify all relevant upstream processes to ensure completeness of the life cycle inventory. This includes not only the direct suppliers to an activity but also the suppliers to those suppliers, extending back through multiple tiers of the supply chain until reaching primary resource extraction from the environment.
The upstream boundary is defined relative to the specific activity or product system being assessed. What constitutes upstream for one study may be downstream or outside the system boundary in another, depending on where the analyst places the focal point of the analysis.
Understanding upstream impacts is particularly important in consequential LCA modelling, where changes in demand for a product may trigger responses throughout the upstream supply chain. These responses can include changes in production volumes, shifts in technology choices, and alterations in market dynamics that extend well beyond the immediate activity being modified.
The term upstream is synonymous with Indirect in LCA terminology, though upstream is more commonly used in practical applications and is more intuitively understood by practitioners.
