Intention, Goal, Scope, Background: Input-Output Analysis (IOA) has recently been introduced to Life Cycle Assessment (LCA). In applying IOA to LCA studies, however, it is important to note that there are both advantages and disadvantages. Objectives: This paper aims to provide a better understanding of the advantages and disadvantages of adopting IOA in LCA, and introduces the methodology and principles of the Missing Inventory Estimation Tool (MIET) as one of the approaches to combine the strengths of process-specific LCA and IOA. Additionally, we try to identify a number of possible errors in the use of IOA for LCA purposes, due to confusion between industry output and commodity, consumer's price and producer's price. Method: MIET utilises the 1996 US input-output table and various environmental statistics. It is based on an explicit distinction between commodity and industry output. Results and Discussion: MIET is a self-contained, publicly available database which can be applied directly in LCA studies to estimate missing processes. Conclusion: By adopting MIET results in existing, process-based, life-cycle inventory (LCI), LCA practitioners can fully utilise the process-specific information while expanding the system boundary. Recommendations and Outlook: MIET will be continuously updated to reflect both methodological developments and newly available data sources. For supporting information see http://www.leidenuniv.nl/cml/ssp/software/miet.
