Biogenic Carbon Accounting in Wood Environmental Product Declarations

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Environmental product declarations (EPDs) are a key mechanism for reporting the environmental impacts of construction materials – including wood products. EPDs are standardized, third-party-verified documents that aim to clearly and transparently report the environmental impacts associated with production, use, and disposal of a product calculated according to standard life cycle assessment (LCA) accounting rules.

Structural wood products are touted globally for their low environmental impacts relative to other fossil-intensive construction materials. EPDs are one mechanism – often used in combination with certifications, owners sourcing requirements, and others – used by the building industry to understand the relative impact of wood products. However, the environmental benefit of biogenic carbon sequestration and storage associated with forest growth and production and use of structural wood products is currently reported differently across regions according to varying accounting mechanisms for wood EPDs in different regions. As EPDs grow increasingly important in the context of global policy and trade, these differences in rules and accounting methods applied to structural wood product EPDs merit greater attention. 

This report dives deep into the accounting and reporting standards for structural and architectural wood product EPDs in Europe and North America with the goal of (1) identifying key challenges in comparability based on current standards and (2) highlighting the largest opportunities to increase the comparability of product category rules (PCRs) and related international LCA standards moving forward. 

The greatest differences between European and North American wood product EPDs stem from differences between these regional parent LCA standards for construction products: EN 15804:2012+A2:2019 (CEN, 2019) and ISO 21930 (ISO, 2017). Despite global agreement on the general framework of EPDs, inherent differences in the emissions and removals included in European and North American wood EPDs prevent direct comparison of products across markets due to their different approaches to quantification and reporting of biogenic carbon removals and emissions. 

Critical aspects of wood product PCRs which currently lack global harmonization include:

• biogenic carbon removals accounting,
• treatment of biogenic carbon emissions and stocks at end-of-life,
• characterization of temporary and permanent carbon storage,
• source forest disclosure requirements,
• land use and land-use change (LULUC) accounting, and
• required environmental impacts and indicators to be reported. 

Despite technical disagreements and temporal misalignment resulting in differences across current regional wood product PCRs, global consensus on the need to improve transparency and accuracy of EPDs is already contributing to international harmonization efforts. Due to the increasingly global nature of construction material supply chains, harmonization of PCRs is necessary to improve global comparability of EPDs. In the near future, current misalignments between regional LCA standards and wood product PCRs may feasibly be remedied leading to vast improvements in global comparability of wood product EPDs and whole building LCA (WBLCA) models for which they are a critical data source.

Ringraziamenti

This research was supported by the Laudes Foundation and the European Climate Fund (ECF). The research originated when the Carbon Leadership Forum, now an independent nonprofit, was hosted at the University of Washington. The research team would like to thank the research staff and graduate students who engaged with this project and helped develop background research including Christina Bjarvin, Brook Waldman, Lieke Droog, and Mel Chafart. The UW team would like to thank the Carbon Leadership Forum for their commitment to disseminating this work.