Dealing with double-counting in tiered hybrid life-cycle inventories: a few comments

Stromman et al. (2009) developed a method for dealing with double-counting in tiered hybrid LCA. Their algorithms identify overlaps of physical and monetary flows in the process and input-output parts of their hybrid data base, and then remove double-counted monetary flows in the input-output system using structural path analysis. Stromman's adjustment criterion is that the set of input-output paths to be removed should have the same monetary value as the process system flow that it overlaps with. I comment on Stromman's methods with respect to the accuracy of the correspondence between process and input-output systems. I argue that the set of double-counted paths to be removed from the input-output system is better selected on the basis of sector definitions than monetary value. (C) 2009 Elsevier Ltd. All rights reserved.