Pre-calculated LCI systems with uncertainties cannot be used in comparative LCA
Summary
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. Therefore, the determination of the distribution that best fits the aggregate LCI is needed. It would help improve the efficiency of storing uncertainty data and performing uncertainty analysis in life cycle analysis (LCA) by saving computation and storage of LCI data.” The authors further illustrate this alleged advantage by an example where computation is reduced from 1000 min to 15 s. This would be great indeed, but the unfortunate fact is that this will not work for “most studies”, because most studies are comparative LCAs, comparing a number of alternative product systems, or comparing an existing product system with a proposed redesign.
