Fuon theory: Standardizing functional units for product design

In order for products to be comparable in different life cycle assessments, functional units need to be defined. Nevertheless, their definitions tend to be simplified or ambiguous. There is thus a need to standardize these functional units, to be properly used for environmental comparison of the environmental performance of products. This paper introduces a systematic approach to define standardized functional units: the concept of fuons. Fuons are defined as an abstraction of a product, based on its essential function and representing the whole set of products that share the parameters for this function's flows. The use of fuons, and by these means the correct definition of the functional unit, should then help to retrieve a suitable product family for life cycle comparison, hence a set of products whose LCA shares a common behavior. This will allow comparing the environmental performance of a new product in development with the products in that family.