Pre-calculated LCI systems with uncertainties cannot be used in comparative LCA

Letter to the editor: A recent paper by Qin and Suh (2016) provides an interesting test of the assumption of lognormally distributed life cycle inventory (LCI) results. We appreciate the importance of this work, and acknowledge that finding out this result must have taken a long computation time. In that respect, we would like to comment on the remark in section 4 that "conducting uncertainty analysis from the unit process level is neither time-efficient nor necessary for most studies.