Abstract
A cradle-to-gate life-cycle inventory was done for 2 by 4 to 2 by 12 dimension lumber produced from logs in the Pacific Northwest (PNW) and Southeast (SE) regions of the United States. Seven mills in the PNW and 11 mills in the SE provided data for 2012 lumber and coproduct production, raw material and fuel use, electricity consumption, and on-site emissions. The mills represented 17 and 11 percent of the production volumes in the regions, respectively. Five processes existed within the mill, log yard, sawing, drying, planing, and energy generation. Data for the first four processes came exclusively from the survey. The functional unit was 1 m3 of planed dry wood. Data for energy generation were based on a nationwide wood boiler survey that included PNW lumber mills. The cradle-to-gate processing energy in the PNW region was 3,434 MJ/m3 of planed, dry lumber, 96 percent of which is owing to log transport and wood processing. The value was higher, 5,151 MJ/m3, for the SE region in part owing to a higher initial wood moisture content. In each region, more than 70 percent of the energy is from bio-based residuals with less than 30 percent from fossil sources. The global warming impact indicator is 58.7 kg CO2 eq per m3 in the PNW and 81.4 kg CO2 eq per m3 in the SE, of which 85 percent is a result of log transport and processing. Planed, dry lumber from the PNW region stores 856 kg CO2 eq per m3 compared with 935 kg CO2 eq per m3 for lumber from the SE region. The coproducts, emissions, and material and energy inputs are further discussed in this article.
