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PARALLEL SESSION 5B: METHODOLOGICAL CHALLENGES FOR CROP PRODUCTION SYSTEMS 8 th Int. Conference on
LCA in the
Agri-Food Sector, 1-4 Oct 2012
Allocation challenges in agricultural life cycle assessments and the
Cereal Unit allocation procedure as a potential solution
Gerhard Brankatschk * , Matthias Finkbeiner
Technische Universität Berlin, Germany
Corresponding author. E-mail: Gerhard.Brankatschk@tu-berlin.de
ABSTRACT
For agricultural life cycle assessments (LCA) several different allocation approaches are currently used. This leads to a broad range
of uncertainty in LCA results (Curran, 2008; Gnansounou et al., 2009; Kim and Dale, 2002; Singh et al., 2010). ISO 14040 and
14044 give guidance on how to deal with allocation situations, but they offer a hierarchy of choices rather than a particular method
(Finkbeiner et al., 2006; ISO, 2006a, b). Specific requirements for an agricultural allocation method were defined and used to test
different allocation approaches. The Cereal Unit was identified as a promising denominator for an agricultural allocation procedure.
Its calculation is mainly based on nutritive properties for animal feeding. It can be applied to all agricultural products. A new allocation
approach for agricultural LCAs, based on the Cereal Unit, is suggested. This approach could help to solve agricultural allocation
problems and might lead to more robust LCA results for services and products originated from agricultural raw materials.
Keywords: life cycle assessment, methodology, allocation, agriculture, by-product
1. Introduction
In recent years the need for the quantification of the environmental impact of products and services has
grown rapidly. This is expressed by increased communication and public awareness about environmental
footprints, such as product carbon footprints (Finkbeiner, 2009), in addition to full LCAs. One risk
associated with this positive development is the fact that most consumers and policy makers are not fully
aware of the uncertainty of LCA results related to methodological choices. Driven by the carbon footprint
discussion, LCA in agriculture has gained increasing interest. There are several methodological
particularities and challenges for agricultural LCAs. Here we focus on the issue of co-product allocation
from agricultural systems.
1.1. Different allocation methods as a source of uncertainty in agricultural LCAs and the need for a new allocation
approach
Different approaches for co-product allocation are one major reason for the uncertainty in LCA results
related to methodological choices (Curran, 2008; Gnansounou et al., 2009; Kim and Dale, 2002; Singh et al.,
2010) To solve the allocation problem, various strategies have been developed, but none is completely
satisfying (Klöpffer and Grahl, 2009).
Agricultural LCAs are particularly error-prone, because allocation often takes place several times. The
errors introduced by each allocation step propagate. Using different allocation methods, Luo et al., (2009)
compare environmental effects of gasoline with those of bioethanol. The outcome is fundamentally affected
by the choice of the allocation method: the results were even inverted by changing the allocation method
from economic to mass or energy allocation. Lundie et al., (2007) state that “more effort needs to be invested
in developing allocation procedures appropriate to specific industry sectors; if possible, physico-chemical
ones”.
Another aspect of the allocation problem is the phenomenon of ignoring or double-counting of
environmental burden. This systematic error might occur if the allocation approaches for two (or more)
LCAs, containing co-products that are grown in the same agricultural system, are not aligned to each other.
As a consequence, the sum of the sub-systems’ burdens is not equal to the total environmental burden of
their common production process. This might not happen if both sub-systems are considered in one study,
because ISO 14040 and 14044 requires using the same allocation approach in one study (ISO, 2006a, b). But
often, LCAs are performed for each sub-product separately. Therefore this effect is likely to occur.
An agricultural example for this phenomenon is the link between dairy and biodiesel production.
Rapeseed meal is used as animal feed and rapeseed oil as raw material for biodiesel. Both are obtained from
the same raw material – rape seeds. If this link is ignored during the calculation of dairy LCA (rapeseed
meal) and biodiesel LCA (rapeseed oil), it is likely that different allocation methods are being used. Fig. 1
shows this phenomenon in quantitative terms. Due to the use of different allocation approaches in separate
assessments – here mass and economic allocation – the sum of the environmental burdens for oil and meal is
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