Page 177 - Materials Chemistry, Second Edition

162 LIFE CYCLE ASSESSMENT HANDBOOK

However, functional units are often defined in a very simplified way or refer to
a single function of the system and not to other possible functions of the same
system (Hirtz, et al. 2003). The choice of the functional unit, however, is not
only a problem faced by those who carry out an LCA of an agri-food product;
it is a choice to be made in any LCA. As a consequence, in many studies on
general aspects of LCA methodology, it is often reported as a problem to be
addressed.
Reap et al. (Reap, et al. 2008), carried out a survey of unresolved problems
in LCA and indicated the functional unit definition as one of the main unan-
swered questions in goal and scope definition, together with the boundary
selection, the social and economic impacts and the alternative scenario consid-
erations. The authors suggest there are several possible sources of error in the
choice of functional units; among them the first and most important derives
from the incorrect transposition of reality in the transition from product sys-
tem to the identification and prioritizing of the functions of that system. In
addition, products often have multiple functions and thus sub-functions that
should be also considered in the definition of a functional unit. In this case
there is a problem regarding what methodology should be followed to choose
a functional unit representing more functions or functional units appropriate
for each chosen function. Cooper (Cooper, 2003) identified three ways that
practitioners proceed to answer this question that naturally led to different
results in the same LCA study.
Other authors have focused on defining some specific aspects of the func-
tional unit, trying to propose solutions to overcome the difficulties. Ciroth &
Srocka (Ciroth & Srocka, 2008) dealt with the search for precision in defining
the parameters of LCA; in particular, since quantitative data are needed in the
definition of some aspects of the functional unit, such as geometric dimensions
and specific weight, the choice of these parameters becomes crucial for the
results of LCI and LCIA. The authors suggest statistical sampling as a method
for obtaining precise and representative estimates for the functional unit, in
order to get empirical estimates for the weight of a product and to reduce
uncertainty in the definition of such an important parameter.
Collado-Ruiz & Ostad-Ahmad-Ghorabi (Collado-Ruiz & Ostad-Ahmad-
Ghorabi, 2010) dealt with the standardization of functional units for product
design. Their analysis is based primarily on the consideration that in the
comparative analysis between products performing similar functions, the
proper definition of a functional unit is crucial. Such definition is not always
done in the best way, but it is often ambiguous and not specific. From this,
the need to standardize the procedure leading to the definition of a func-
tional unit and thus the authors introduce the "Fuon" theory. The authors
state that: "Fuons are defined as an abstraction of a product, based on its
essential function and representing the whole set of products that share the
parameters for this function's flows. The use of fuons, and by these means,
the correct definition of the functional unit, should then help to retrieve
a suitable product family for life cycle comparison, hence a set of products
whose LCA shares a common behaviour. This will allow comparing the