Page 19 - Materials Chemistry, Second Edition

1.1 What Is Life Cycle Assessment (LCA)? 3

9)
activity. In an LCA, systems that serve a specific function and therefore have a
specified performance are analysed.
Therefore, the quantified performance (avail) of a product system is the intrinsic
standard of comparison (reference unit). It is the sole correct basis for the definition of a
‘functional unit’. 10)

1.1.3
Functional Unit

Besides the cradle-to-grave analysis (thinking in terms of systems, life cycles or
production trees), the functional unit is the second basic term in an LCA and is
therefore to be explained here.
The function of a beverage packaging, for example, is – besides shielding of
the liquid – above all, transportability and storability. The functional unit is most
frequently defined as the provision of 1000 l liquid in a way to fulfil the tech-
nical aspects of the performance. This function can, for instance, be mapped
with different packaging specifications (the following examples are arbitrarily
chosen):

• 5000 0.2 l 11) pouches
• 2000 0.5 l reusable bottles of glass
• 1000 1 l single-use beverage carton
• 500 2 l PET (polyethylene terephthalate) single-use bottles.

Thus, for a comparison of packaging systems, the life cycle of 5000 pouches, 2000
reusable glass bottles, 1000 cardboards and 500 2 l PET bottles, which are four
product systems that roughly fulfil the same function, needs to be analysed and
compared.
Slight variations in performance (convenience, e.g. weight, user friendliness,
aesthetics, customer behaviour, suitability as advertising medium or other side
effects of packaging systems) are not important in this simplistic example. It is,
however, important to note that systems (not products) with matchable functions are
compared. This is the reason why tangible products (goods) can also be compared
12)
with services, as long as they have the same or a very similar function. Within an
LCA, products are defined as goods and services. As with goods, services require
energy, transport, and so on. Therefore, it is possible to define services as systems
and compare them with tangible products on the basis of equivalent function by
means of the functional unit.

9) SETAC (1993a).
10) Fleischer and Schmidt (1996); see ISO 14040 (2006a).
3
11) 11 = 1dm .
12) Boustead (1996).