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preferences for the first are found (
Marienstein
)
,
though at both locations
no clear ranking for all years was identified (Figure 3.3).
4. SOME POINTS OF DISCUSSION
4.1 Methodical approach of energy accounting
Energy calculations always include some degree of uncertainty. Absolute
figures can be substancially influenced by
the energy coefficients used
the algorithms applied to estimate quantities for substance flows not
measured,
e.g.
the specific fuel use of each work
details of the system boundaries, such as substance flows or processes
which were excluded by definition.
Therefore, a framework for comparisons with other results must be
carefully prepared. The ranking of the farming systems in the investigated
energy criteria is in general not influenced by changes in the underlaying
energy coefficients. The used cropping data were calculated with five
alternative energy data sets from other studies without major differences in
the general system ranking (Moerschner 2000).
When the gross energy incorporated in the seeds is subtracted from
the total energy yield, as suggested in this study, the related substance and
energy flows don't have the same physical basis. This causes some
problems in terms of LCA-methodology. This way of calculation was
chosen for better comparison with other energy studies on the input side.
When data for LCA-applications should be provided, it may be a better
solution to include the inherent energy of seeds into the energy coefficients
used and indicate the share of incorporated solar energy and process
energy. However, in the presented energy analysis the relations between
the systems are not sensitive to such a change.
Machinery is often excluded in energy use studies of farming
systems. In economic interpretations, capital goods are counted as fixed
costs that are not included in gross margins. In this case study machinery
was included because changes in cultivation intensity also cause impacts
on the annual intensity in farm machinery use on a given area. As
consequence, a reduced cultivation intensity should result in a reduction of
applied farm machinery as well, because otherwise, their depreciation
becomes an important energetical load within
total energy budgets
(Moerschner 2000).
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