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Research Paper FPL–RP–707 6 Figure 3. Schematic diagram of a block pallet. 1.2.2 System Boundary This project considered the cradle-to-grave system boundary analyzing the whole life cycle of a wooden pallet from resource extraction (cradle) to disposal (grave). The wood flow of a generic wooden pallet is presented in Figure 4. The system boundary showing the wood flow was established to represent current production in the United States to cover different manufacturing processes. The system boundary begins with forest regeneration and ends at the end-of-life stage of a wooden pallet. Wooden pallets are generally manufactured from either hardwood (HW) or softwood (SW) rough sawn lumber and precut lumber. The common species used in pallet manufacturing in the United States are listed in Appendix A. The raw material acquisition stage includes site preparation and planting seedlings, forest management including fertilization and thinning, harvesting, transportation of saw logs to the lumber manufacturing facility, and lumber production itself. Lumber production includes mainly production of rough sawn SW and HW lumber from incoming saw logs with some kiln-drying of SW lumber. In addition to HW and SW lumber use, a small amount of plywood and oriented strandboard (OSB) were reported by some facilities. A variety of wooden pallets are produced in the United States differing in their size, design, and function. The pallet manufacturing phase covers common processes of pallet production, i.e., wood preparation and board shaping (cutting of lumber to appropriate size and notching), assembly, heat treatment, painting, and stamping at the pallet manufacturing facility. Cutting of lumber to size may be performed at the lumber manufacturing facility, yet it is considered in the pallet manufacturing system boundary. Depending on the desired use of the product, some additional processes may be included in the system boundary such as heat treatment or stamping. Heat treatment or chemical treatment may be used to comply with International Standards for Phytosanitary Measures No. 15 (ISPM 15) (FAO 2009) if pallets are used for international consumption or by customer request. Use of wood in pallet manufacturing has environmental benefits because it is a renewable material, i.e., it may be recycled or reused. After the use phase and an inspection, some pallets are reused by consumer product manufacturers. Although roughly 13% of the pallets produced in 2016 were received by solid waste disposal facilities, only about 5% of these pallets were eventually landfilled because of diversion practices such as grinding for use as mulch or fuel (Shiner 2018, Gerber 2018, Gerber and others 2020). The other 87% were received by the repairing–remanufacturing facilities. At the repairing–remanufacturing facilities, about 53% of the recovered pallets were repaired and about 12% were reused without repair. This number was lower in Park and others (2017), who reported 84% of damaged stringer (GMA-style) pallets received were repaired for reuse excluding pallets reused as is. Block pallets were not considered by Park and others (2017), which would probably affect this 84% value. Pallets are repaired through the refastening of connections or replacement of damaged pallet components. Sometimes, pallets are dismantled and used for repairs and remanufacturing. About 31% that could not be reused or repaired were dismantled for reuse in reconditioned pallets or ground for other uses. The rest of the pallets, about 4%, were ground and used for other purposes. Wood from dismantled pallets displaced the virgin material coming into the pallet manufacturing supply chain. This displacement offset the environmental burden resulting from producing lumber along with forest management and harvesting operations by extending the service life of the pallet and pallet parts. The rest of the wood material that could not be used in repairs were ground and used for applications such as fuel, mulch, or animal bedding.

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