samedi 21 février 2009

LCA for six types of grocery bags

Are biologically-derived materials always best? i.e., are materials derived from plant sources more environmentally friendly than materials are derived from (fossil fuel) petroleum?

Designers (in the various design professions) should not assume this generalization about biomaterials to be true. In many cases, plant-derived materials are more renewable and can be more ecologically responsible than petroleum-derived materials. In many other cases, however, plant-derived materials can be more resource intensive and/or more ecologically damaging than their petroleum-derived counterparts.

Let’ s look at grocery bags as an example. We’ve compared six grocery bag alternatives, listed below. After each of the bag materials is a manufacturing method. If used, the approximate weight of bags needed to carry 20 lbs of groceries, and the assumed waste distribution at the end of the life of the bag. The functional unit is Okala impacts (in millipoints) per delivery of one cycle of 20 lbs of groceries.
Although this is not an exhaustive or comprehensive study, it is a clear example of how biologically-derived materials can perform more poorly than petroleum-derived materials. There are, no doubt, situations in which bio-materials deliver superior environmental performance. Designers should consider the complexity of the life cycle of materials, including land-filling, before assuming that biologically-derived materials are always superior to their fossil-fuel based counterparts.

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