Wooden and Plastic Pallets: A Review of Life Cycle Assessment (LCA) Studies

Pallets are the tiny cogs in the machine that drive transportation in the global economy. The profusion of pallets in today's supply chain warrants the investigation and discussion of their respective environmental impacts. This paper reviews the life cycle assessment studies analyzing the environmental impacts of pallets with the intent of providing insights into the methodological choices made, as well as compiling the inventory data from the studies reviewed. The study is a meta-analysis of eleven scientific articles, two conference articles, two peer-reviewed reports, and one thesis. The review was implemented to identify the key methodological choices made in those studies, such as their goals, functional units, system boundaries, inventory data, life cycle impact assessment (LCIA) procedures, and results. The 16 studies reviewed cumulatively analyzed 43 pallets. Mostly pooled (n = 22/43), block-type (n = 13/43), and wooden (n = 32/43) pallets with dimensions of 1219 mm x 1016 mm or 48 in. x 40 in. (n = 15/43) were studied. Most of the studies represented pallet markets in the United States (n = 9/16). Load-based (e.g., 1000 kg of products delivered), trip-based (e.g., 1000 trips), and pallet-based (e.g., one pallet) functional units were declared. A trip-based functional unit seems the most appropriate for accounting of the function of the pallets, as its purpose is to carry goods and facilitate the transportation of cargo. A significant amount of primary inventory data on the production and repair of wooden and plastic pallets are available, yet there are significant variations in the data. Data on pallets made of wood-polymer composites was largely missing.