AGRICULTURAL REFERENCE SYSTEMS IN LIFE CYCLE ASSESSMENTS - Economics of Sustainable Energy in Agriculture - page 98

underlying principles. This was done in detail in the study underlying the
present work (Jungk and Reinhardt 2000).
The purpose of an LCA is to assess the environmental impact of
every step in the life cycle of a particular product ('from cradle to grave').
This includes the necessity of defining all influences by that product with
respect to an alternative product. Therefore in theory any process that
involves a change in land use requires the consideration of a reference
system. In the case of buildings however, such as factories or oil rigs, the
land area taken up is very small in comparison to the product output, while
in the case of forestry or agriculture the ratio is different, since relatively
large areas are required.
It is the purpose of this chapter to provide a definition of the
agricultural reference system and to deduce certain principles that should
be followed in order to designate an appropriate reference system for an
agricultural product. Note that land use change will not be considered as an
indicator in LCA, but is the consequence of the choice of system
boundaries. Furthermore, examples were chosen which demonstrate the
effect of different reference systems on the environmental impacts of
bioenergy carriers. These examples were based on rape seed methyl ester
(RME) for biodiesel as one of the most widely used forms of bioenergy.
For this purpose, complete life cycle analyses were carried out for RME
and diesel from fossil fuel, which were then compared within different
contexts, i.e. using different reference systems. The examples were
calculated following the ISO 14040-41 standards (DIN EN ISO 1997 and
DIN EN ISO 1998). For every example a life cycle inventory (LCI) was
carried out with regard to selected parameters, and partly also a life cycle
impact assessment (LCIA). These two elements are parts of a life cycle
analysis (LCA). An LCA can be carried out for a single product or it can
compare the life cycle impacts of two products, which was done in the
examples below. Figure 8.1 is a schematic representation of a whole life
cycle of an agricultural bioenergy carrier including the reference system as
well as the system serving as a comparison, namely conventional diesel
fuel.
2. DEFINITION AND RELEVANCE OF
AGRICULTURAL REFERENCE SYSTEMS WITHIN
LCA
Why is it at all necessary to take a reference system into account? The
following example may clarify this point: if an LCA is to be carried out for
a certain amount of rape seed methyl ester (RME) to be used as biodiesel in