Multifunctionality in Life Cycle Inventory Analysis: Approaches and Solutions

This chapter gives an overview of the mainstream approaches and solutions to the problem of multifunctionality in the Life Cycle Inventory (LCI) phase. Many industrial processes are multifunctional. Their purpose generally comprises more than a single product or service. Practitioners in Life Cycle Assessment (LCA) are thus faced with the problem that the product system(s) under study provide more functions than the one investigated in the functional unit of interest. Among others, an appropriate decision must therefore consider which economic and environmental flows of the multifunctional process or system are to be allocated to which of its products and services. The discussion on multifunctionality goes back to energy analysis (a precursor of LCA), and several of today’s well-known solutions for the multifunctionality problem origin from this time. There is no generally accepted solution for the multifunctionality problem, and it is even hard to imagine that there will ever be a solution. On the other hand, it is generally recognized that different solutions may considerably influence LCA results depending on the exact position of the multifunctional process in the product’s flow chart. As a consequence, sensitivity analyses should be applied to test the influence of different solutions. An issue that deserves more attention is the fact that most LCA case studies so far apply one of the solutions without properly justifying where and what exactly the multifunctionality problem is and which criteria are used for determining that. In this chapter, these steps are therefore distinguished, explicitly aiming for more transparency in the discussion on multifunctionality approaches and solutions.