Reviewing the variability in product category rules for asphalt pavements - A quantitative evaluation of methodological framework differences for environmental product declarations

The road construction industry is exploring the use of environmental product declarations (EPDs) as a communication tool and their implementation in green public procurement (GPP). Currently, several product category rules (PCRs) specific to asphalt mixtures exist worldwide. Consequently, the objective of this paper is to assess the similarities and differences between these PCRs to avoid comparing EPDs derived from inconsistent methodological frameworks. This research revealed similarities in requirements for data quality, exclusion of inputs and outputs, and allocation procedures. However, it also showed major differences in the use of system boundaries, reference service life (RSL), functional unit (FU), and end-of-life (EOL) modelling. A quantitative evaluation of the variability of the PCRs showed that an RSL in its current form only provides information about the expected performance but does not alter environmental impacts in the final EPDs. Therefore, it is advised to recalculate the results into impacts per year. Furthermore, it was found that applying a cut-off for a rejuvenator and SBS influences the total GWP impact in module A1 by +25% and -30%, respectively. Finally, if an EPD uses a cradle-to-grave or cradle-to-cradle scope, relocating the EOW does not affect the total impact but only triggers a shift of impacts between the EOL and material modules (it can increase the total GWP impact by 25% if the focus is A1-A3). The overall conclusion is that selecting a specific PCR for asphalt mixtures influences the underlying methodological framework and that harmonisation of the PCRs is consequently recommended.