Life Cycle Assessment of Wooden Interior Doors in Germany: A Sector-Representative Approach for a Complex Wooden Product According to EN 15804 Methodology

Based on the standards, International Organization for Standardization (ISO) 14040/44 and EN 15804, a cradle-to-gate analysis with an end-of-life scenario was carried out to provide a sector-representative environmental product declaration (EPD) for wooden interior doors according to the new standard, EN 15804. Methodological challenges caused by the complexity of the product system and the objective of representativeness are discussed. Primary inventory data were collected at 19 door production sites and covers 87% of the total German door production. The life cycle assessment was conducted using generic data for wooden materials, which is in line with EN 15804 derived from the okoHolzBauDat project. Additionally, generic data from GaBi Professional and ecoinvent databases were used. Besides the estimation of fossil carbon dioxide emissions, the biogenic carbon content of the wooden biomass was taken into account. The highest environmental impacts originate from manufacturing the semifinished wood products and fittings in the prechains. A sensitivity analysis reveals uncertainties up to 17% in the EPD results. These can be attributed to the use of the partly inadequate linear scaling of the life cycle inventory by a factor of 1.57 to fit the required size of the functional unit given by the relevant product category rules. The consideration of biogenic carbon embodied in the wooden biomass leads to very high manufacturer-specific deviations to the averaged global warming potential results when cradle-to-gate stages are considered only.