An activity output is an exchange from an activity to another activity or to the environment. These outputs represent the flows of materials, energy, products, emissions, and waste that result from an activity's operations and exit to become inputs for other activities within the product system or to be released into the natural, social, or economic environment.
Activity outputs can take various forms depending on the nature of the activity. They may include finished products, co-products, by-products, materials for treatment, waste streams, emissions to air, water, or soil, and other environmental releases. These outputs connect activities within a product system by linking production stages, with the output of one activity often serving as the input to subsequent activities in the supply chain.
It is important not to confuse activity output with gross or net economic output, which are distinct concepts used in economic analysis. Gross economic output refers to the total monetary value of products generated by an activity, including subsidies, whilst net economic output relates to value added after subtracting intermediate costs. Activity output, in contrast, describes the physical and elementary flows leaving an activity, regardless of their economic valuation, making it a fundamental concept for tracking material and energy balances in life cycle assessment.
