LCA Food 2012 in Saint Malo, France! - Manifestations et colloques ...

PARALLEL SESSION 5B: METHODOLOGICAL CHALLENGES FOR CROP PRODUCTION SYSTEMS8 th Int. Conference on LCA in the
Agri-Food Sector, 1-4 Oct 2012
not equal to the total environmental burden of the seeds. In the first example (Fig. 1, left side), 37% of the
total environmental burden is being ignored by the assessments.
Figure 1. Left: Unintended ignorance of environmental burden due to different allocation approaches for byproducts
from the same agricultural system; Right: Unintended double-counting of environmental burden
due to different allocation approaches for by-products from the same agricultural system. Grey and black
areas represent environmental burden. Dotted lines indicate initial environmental burden (100%) and
overhanging bars represent double-counted environmental burden.
The opposite effect can also be observed (Fig. 1, right side). Here the LCA practitioner might end up with
an environmental burden sum for oil and meal of 117% instead of the 100% from the seeds, i.e. 17% of the
burden is double-counted. That means the sum of environmental burden of one agricultural system cannot be
calculated by adding up the environmental burdens of the sub-systems when different allocation methods are
used. For the general interpretation of agricultural LCAs this aspect carefully needs to be considered. In
terms of a contribution for solving the allocation problem for agricultural purposes, in the next chapters a
new allocation approach is described.
2. Methods
2.1. The Cereal Unit and its use as new allocation approach
In the past, different estimation approaches for agricultural productivity were discussed. A simple sum of
the masses of all agricultural products was recognized to be an inappropriate solution, because different levels
of efforts for the production, various functionalities of the products and fulfilment of services would be
neglected. To make agricultural productivity better comparable and measurable, it was realised that a
weighted sum rather than a sum of masses is necessary (Becker, 1988). For this aggregation step, one common
denominator with a conversion key is necessary. Amongst others, the Cereal Unit is one such common
denominator for the aggregation of agricultural data. The Cereal Unit was developed by German agricultural
authorities decades ago in the field of agricultural statistics and is continuously updated (Becker, 1988;
BMELV, 2012; Klapp, 2011; Mönking et al., 2010). Using this Cereal Unit as common denominator, all
agricultural products and by-products can be brought to the same level and thereby become comparable. We
suggest using this Cereal Unit as a basis for allocation in agricultural Life Cycle Assessments.
The calculation of the Cereal Unit is mainly based on the feeding value of agricultural products. Calculation
example: For barley the animal specific metabolisable energies [MJ ME / kg fresh weight] (a common
parameter in animal feeding; cattle: 11.30; pigs: 12.63; etc.) are being weighted, using the share of actual
feeding practices of barley (here for German conditions; cattle: 5%; pigs: 94.5%; etc.). Result is the specifically
aggregated metabolisable energy content of 12.56 MJ ME / kg barley. This value was defined as
1 Cereal Unit (therefore formerly also called barley unit). The specifically aggregated metabolisable energy
contents for other products are compared with the value of barley. This comparison leads to the crop specific
Cereal Unit. For wheat the specifically aggregated metabolisable energy content is 13.06 ME MJ / kg wheat
– therefore 1 kg wheat equals 1.04 Cereal Units.
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