Functional unit
The amount of service an LCA's results are expressed per, such as product delivered.
In life-cycle assessment, the functional unit is the quantity of service that results are expressed against. Choosing it well makes comparisons fair: two pallets that carry different loads for different numbers of trips should be compared per amount of product delivered, not per pallet.
The USDA's wooden pallet LCA used 100,000 lb of product delivered on pallets as its functional unit, and reported about 10.4 kg CO2e per functional unit on average, cradle to grave.
When you read a wood-versus-plastic comparison, check its functional unit first. A per-pallet result hides the number of trips; a per-delivery result builds it in. See wood vs plastic.
Functional units also matter when a supplier quotes a carbon figure for its pallets: ask whether it is per pallet, per trip or per ton of goods moved, and over how many trips. A per-pallet figure for a block pallet built for many trips will look worse than a light one-way pallet, even when it carries far more product over its life.
Sources
- Cradle-to-grave life-cycle assessment of wooden pallet production in the United States (Res. Pap. FPL-RP-707) USDA Forest Service, Forest Products Laboratory (Alanya-Rosenbaum and Bergman, 2020). Accessed October 27, 2026. Table 2 (p. 8): average weights of 48×40 in. designs.