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Cradle-to-Grave Life-Cycle Assessment of Wooden Pallet Production in the United States 11 Table 7—Mass balance of new wooden pallet manufacturing Unit Weighted average Mass (%) CoV w (%) Wood input Hardwood precut lumber OD kg/pallet 1.68 8.0 200 Hardwood lumber OD kg/pallet 5.04 24.0 115 Softwood precut lumber OD kg/pallet 1.67 7.9 189 Softwood lumber OD kg/pallet 12.45 59.2 84 Plywood OD kg/pallet 0.15 0.7 413 Oriented strandboard OD kg/pallet 0.02 0.1 736 Total input OD kg/pallet 21.01 Wood output Sawdust OD kg/pallet 1.45 6.8 94 Hogged material OD kg/pallet 0.92 4.3 155 Wood chips OD kg/pallet 1.10 5.2 190 Scrap wood OD kg/pallet 0.01 0.0 1,552 Shavings OD kg/pallet 0.29 1.4 473 Pallet OD kg/pallet 17.50 82.3 101 Total output OD kg/pallet 21.25 material, wood chips, scrap wood, and shavings. Electricity consumption for the precut lumber received by the facilities was accounted for in the gate-to-gate system boundary and was adopted from Bergman and Bowe (2011). The wooden pallet boards produced were assembled using fasteners at the assembly–nailing unit process. Fasteners used in the facilities include staples, nails, bolts, and screws. Some additional processes may be included in the manufacturing of the wooden pallet depending on the desired final product. These optional processes include heat treatment, painting, and stamping. Primarily, natural gas and propane were used as heat treatment fuel, and about 21% of the new pallets produced were heat-treated. Weighted industry-average inputs and outputs of the additional processes are provided in Table 10. 2.6 Use Stage and Pallet Repair– Remanufacturing (B1, B2) These informational modules cover the time from when the pallet leaves the production stage [A3] until it reaches end-of-life [C]. Use stage [B1] of wooden pallets for transportation and warehousing of goods is subject to high variability and uncertainty. Therefore, in line with the PCR because no primary data were collected, it was not included in the system boundaries. Regardless, we presented GHGs from the use phase using hypothetical data in Section 3.2 Additional Environmental Information. The GW impacts resulting from the use phase were calculated assuming (1) an average of 50 km, (2) a low of 25 km, and (3) a high of 100 km. For the repair and reuse stage [B2], Table 11 presents the gate-to-gate process flows developed for the pallet repair– remanufacturing. Transportation to the facility from the user was accounted for in the analysis. The data collected from the facilities showed that the weighted-average distance that the pallets were transported was about 65 km. Based on data reported from the repair–remanufacturing survey, a majority of the pallets were repaired (about 53%, at the facility). For the remaining 47%, about 12% were reused without repair, 31% were dismantled, and 4% were used for other purposes. About 37.3% of the boards from the dismantled pallets were recovered and used for repairs and remanufacturing. The rest of the dismantled pallets that could not be reused were ground and repurposed as mulch, fuel, or animal bedding. 2.7 End-of-Life Phase and Potential Environmental Benefits (C, D) At the end-of-life (after the use phase), about 13% of pallets were sent to solid waste disposal facilities, where only about 5% of this total were actually landfilled because of diversion practices. For the rest of the pallets, 37.3% of them were dismantled and the remaining pallets were ground and beneficially used for mulch, animal bedding, or energy. The end-of-life analysis was performed based on the weighted average of the four pallet types (Table 12). For the recyclable material, the cut-off method was used for the impact assessment analysis. Beneficially used coproducts and end-of-life material were calculated and presented under Module [D]. Module [D] represents the potential avoided production of primary materials in the technosphere by beneficial use of material outputs from the product life cycle. In this study, beneficial use wood coproducts from Module [A3] and product disposed at [C3] were accounted for. This included the reuse of dismantled boards replacing virgin lumber coming in and wood fuel used in boilers replacing natural gas. For wood fuel used in wood boilers to replace natural gas, the boiler efficiencies were assumed

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