Page 102 - Materials Chemistry, Second Edition

8 Scope Definition 87

As an example, glass and PET in beverage packaging have different densities
and physical properties, and different masses will therefore be required for
providing the same function. To prevent mistakes like this, the functionality
of the product should be considered (for example, what is the functionality of
packaging?).
2. Being overly restrictive:
Example: “Enable watching of television with a 30 W power consump-
tion for 10,000 h”
Explanation:A fixed power consumption is (except in special cases) not
relevant to the user of a television and means that only televisions with that
exact power consumption can be included in a study. To prevent mistakes
like this, it must be ensured that the functional unit only covers what relates to
the function of the product (to watch television).
3. Incorrect use of technical standards or legal requirements:
Example: “Driving 1000 average person-kilometres in a diesel passenger
car that fulfils the Euro 6 standard and therefore emitting less than 0.08 g
NO X per kilometre (Euro 6 standard) during use”
Explanation: Often products can demonstrate compliance with the law or
a voluntary standard when completing a test that does not represent the actual
conditions of the product’s use. A passenger car complying with the Euro 6
standard may emit more NO X than 0.08 g/km, depending on the driving
pattern, climate, etc. A misinterpretation of a technical standard in the
functional unit can therefore lead to mistakes in the LCI (in this case,
underestimated NO X emissions). To prevent mistakes like this, the condition
of the use must be considered. Generally, a reference to a technical standard
in the functional unit does not need to be accompanied by the exact meaning
of the technical standard, as this will be dealt with in the LCI modelling step.

It must be stressed that a solid insight in the relevant technological domain is
required to define a meaningful functional unit. For example, good knowledge
about biofuels, nanomaterials or remediation of contaminated sites is required to
define meaningful functional units for these technologies. Chapters 26–36 discuss
the application of LCA, including the definition of functional units, for a wide range
of technological domains.

8.4.3 Reference Flows

When the functional unit has been defined, the reference flows can be determined.
A reference flow is the product flow to which all input and output flows for the
processes in the product system must be quantitatively related. In other words, the