Page 68 - Materials Chemistry, Second Edition

50 LIFE CYCLE ASSESSMENT HANDBOOK

Example: Shipping containers. The function of a shipping container
is to deliver an undamaged quantity of goods. Therefore, for con-
tainers that have equivalent capacity and provide equivalent prod-
uct protection, an appropriate functional unit might be defined as
1,000 container shipments. If the containers being compared are a
single-trip container and a reusable container, it is important to con-
sider all the differences involved in making an equivalent number of
shipments in each type of container.
For the single-use container, each time a shipment is made, a con-
tainer must be manufactured and shipped to the filler. At the end
user destination, the emptied container must be managed by recy-
cling, landfill disposal, or combustion.
For the reusable container, the number of containers that must be
manufactured for a given number of shipments depends on many
factors including the percentage of containers that are lost or sto-
len during use, damage rates, fate of damaged containers (repaired,
recycled, or disposed), and lifetime uses for containers that remain
in circulation. Although fewer reusable containers must be manufac-
tured for a given number of shipments, there are additional impacts
associated with reuse that are not required for disposable contain-
ers. Reusable containers must be backhauled to the filler or to an
inspection point. Backhauling may be done on a truck that is already
returning from a retail store to a distribution center, or a special back-
haul trip may be required. Reusable containers may require cleaning
or reconditioning before they can be returned to use, which adds
environmental burdens for materials and energy used in the clean-
ing process. Depending on where the cleaning takes place, additional
transportation may also be required.

Other differences between systems may involve a combination of physical
differences and consumer behavior. Consider the example of two ice cream
cartons that hold an equivalent volume of product. Carton A is cylindrical with
a lift-off lid, and Carton B is rectangular, with a paperboard flap closure. Carton
B can be packed more compactly in a store freezer, so that less shelf space is
required for ice cream packaged in Carton B compared to the same quantity
of ice cream packaged in Carton A. Because Carton A occupies more freezer
space per unit volume of ice cream, Carton A is allocated a larger share of the
daily energy requirements for operating the store freezer. However, consumers
tend to prefer Carton A's removable lid design over Carton B's paperboard
flap closure. If consumer preference for the Carton A design translates into fas-
ter sales compared to Carton B, the reduced time in the retail freezer for Carton
A may offset its additional freezer shelf space requirement. When consumer
behavior is involved, it is advisable to conduct a sensitivity analysis unless
data are available to reliably characterize actual consumer behavior.
Geographic Boundaries. The geographic boundaries of the system influence
factors such as raw material sourcing, technology used, electricity grids, and