Life-Cycle Inventory Analysis of I-joist Production in the United States

Abstract

Documenting the environmental performance of building products is becoming increasingly common. Creating environmental product declarations (EPDs) based on life-cycle assessment (LCA) data is one approach to provide scientific documentation of the products’ environmental performance. Many U.S. structural wood products have LCA-based “eco-labels” developed under the ISO standard 14025. In this study, the standard dictates underlying life-cycle inventory (LCI) data to be used reflect current practices in the industry. Therefore, gate-to-gate manufacturing LCI data for I-joist must be developed to construct updated cradle-to-gate LCAs for southeastern (SE) and for Pacific Northwestern (PNW) regions of the United States. Modeling the production weighted-average primary industry data per 1.0 km of I-joists with an assumed average depth of 30 cm through LCI analysis provides cumulative energy consumption and environmental outputs. For PNW and SE, cumulative mass allocated energy consumption associated with manufacturing 1.0 km of I-joist was found to be 65.7 and 71.0 GJ/km, respectively, with about 30% of the primary energy provided from wood residues. Emission data produced through modeling found that estimated biomass and fossil CO₂ emissions in kg/km were, respectively, 1,774 and 1,969 for the PNW and 1,808 and 2,042 for the SE. One km (4,437 oven-dry kg wood portion, on average) of I-joist stores about 8,130 kg CO₂ equivalents. The amount of carbon stored in I-joists thus exceeds total CO₂ emissions during manufacturing by about 215%. From this study, the gate-to-gate I-joist manufacturing LCI data can now be incorporated into the cradle-to-gate LCAs to develop an updated EPD.

Citation

Bergman, Richard D. 2015. Life-Cycle Inventory Analysis of I-joist Production in the United States. In: Proceedings of the 58th International Convention of Society of Wood Science and Technology June 7-12, 2015 - Grand Teton National Park, Jackson, Wyoming, USA pp. 167-175.