PSILCA database for social life cycle assessment: worker hours vs. raw values approach

Abstract Purpose Progressive development within the research area of social life cycle assessment (S-LCA) has recently occurred, for example, GreenDelta introduced a new direct quantification approach using raw values in the PSILCA database. This complements the concept of the activity variable worker hours, which has many advantages and disadvantages. This paper aims to assess this new approach by identifying its characteristics, opportunities, and challenges in comparison to the initial worker hours approach. Methods The general use of activity variables in S-LCA is outlined, followed by an elaboration of the characteristics, purposes, and functionalities of the worker hours approach as well as the raw values approach of PSILCA. This comparison of approaches includes different data components, calculation procedures, and their upsides and downsides and is based on materials provided by GreenDelta as well as our own elaborations. Two components of a fuel cell electric vehicle, the glider and the proton exchange membrane fuel cell, serve as sample applications for the comparison and are briefly described before their calculation is executed in the software openLCA, using both PSILCA approaches. The question of whether the differences in the approaches contradict a comparison is answered: The PSILCA results of the sample applications can be compared to derive further characteristics. Results and discussion The comparison comprises two modeling requirements for the raw values approach as well as their major consequence. They concern the execution by the practitioner: inventory indicators must be added to every unit process, the choice of inventory indicators must be the same for every unit process, the amount of the reference flow in the output always has to equal “1 USD,” and consequently, the number of unit processes has an influence on the results. Furthermore, the results of the S-LCA sample applications reveal that the direct impacts in the raw values approach tend to be greater than those in the worker hours approach. The reason can be found in the different calculation procedures as well as the different variables included. Conclusions Both approaches have benefits and drawbacks. Depending on the goal of the study to be pursued, the one or the other might be advantageous. In both cases, it is key to understand the modeling requirements and the calculation approach used to interpret the PSILCA results.