Does it matter which Life Cycle Assessment (LCA) tool you choose? – a comparative assessment of SimaPro and GaBi

SimaPro and GaBi are the leading software tools used for life cycle assessments. Assessing product systems applying the exact same unit process foundation would be expected to yield comparable result sets with either tool. The software performances are compared based on a random sample of 100 unit processes. The research question investigated here is; can there be a difference between SimaPro and GaBi influencing the results and the decisions based on them? In many cases the results are identical between SimaPro and GaBi or nearly so, but in other cases the results reveal differences. Some of these differences are so large that they could influence the conclusions. For some of the 100 unit processes, six elementary flows were inventoried differently in SimaPro and GaBi, with an extreme maximum comparative ratio of 109. The implementation of the impact assessment methodologies shows notable differences. For the same life cycle inventory the maximum result ratio for the characterized results is 0.0076 for Terrestrial Ecotoxicity Potential. The observed differences appear to originate primarily from errors in the software databases for both inventory and impact assessment. SimaPro and GaBi are used by many Life Cycle Assessment (LCA) practitioners worldwide as a decision-support tool; if the results of the present analysis are representative of the differences obtained when using either one or the other, then the implications of this paper are worrying. It is clearly in the interest of both software developers and LCA practitioners that the observed differences be addressed, for example through ring tests comparing the tools.