A critical analysis of inconsistencies in GWP flows in mass timber product EPDs in the European market

PURPOSE The paper examines the carbon flow throughout the life of mass timber products available on the European market to detect the coherence of the information communicated by the considered EPDs and to understand their comparability. METHODS The study focusses on 60 EPDs of CLT, GLT, LVL, and other structural timber products covering all the EPDs available that meet the requirements defined in the paper. The GWP flow is tracked for all the products described and all the end-of-life scenarios defined, from the sequestration of atmospheric CO2 during the growth of the tree through the end-of-life scenario(s) and D module. The biogenic carbon content is verified against the theoretical value and end-of-life scenarios are commented against the cascading hierarchy of timber reuse, recycling, energy harvesting, and landfilling. RESULTS AND DISCUSSION Discrepancies are observed and commented in the treatment of biogenic carbon, end-of-life (EoL) scenarios, and compliance with EN 15804 standards, leading to significant variations in reported environmental impacts. Key findings reveal that GWP values are often oversimplified or inconsistent, particularly in stages involving biogenic CO2 release and EoL impacts, thus hindering the comparability of EPDs. Several practical recommendations are provided for industry practitioners to evaluate EPD reliability, with a proposed method to help EPD users interpret these documents from a critical perspective. CONCLUSIONS The inconsistencies identified in many of the monitored EPDs hinder their comparability and their use by practitioners. Also, they may compromise the accuracy and reliability of the results obtained by their use to conduct life cycle analysis of buildings. The paper highlights areas of further research to enhance the utility and credibility of EPDs in promoting sustainable construction.