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

PARALLEL SESSION 4A: CARBON FOOTPRINT 8 th Int. Conference on LCA in the
Agri-Food Sector, 1-4 Oct 2012
which should be included in the assessment since these inputs might be very different between crops. Thus,
the environmental burdens and benefits need to be divided and allocated to the specific crops. According to
the ISO standards for LCA (ISO 14040 and 14044) allocation ‘...wherever possible should be avoided by
dividing the unit process in two or more sub processes...’. In a conventional crop rotation, this is often no
problem and the analysis can be focused on the crop specific inputs and outputs i.e. crop yields. Likewise, in
simple organic rotations without green manure and catch crops (Knudsen et al., 2010) or organic perennial
crops, that do not imply other crops (Knudsen et al., 2011), it is possible to focus on the specific crop. The
advantage of this approach is that the crop-specific inputs will be reflected in the carbon footprint of the
crop, such as e.g. high diesel consumption in the potatoes. If it is not possible to subdivide the unit process,
i.e. the crop rotation, and economic or mass allocation is performed to allocate the environmental burden
among the different sales crops, the crop specific inputs would not be reflected. This would mean that e.g.
high diesel consumption in the potatoes, would also burden the e.g. spring barley that happens to be grown in
the same crop rotation.
Therefore, in order to calculate carbon footprint values for the specific crops, we recommend subdividing
the crop rotation in the specific crop productions. The challenge is then how to divide the environmental
burdens and benefits from the green manure and catch crops. This could be done either on a per hectare basis
or based on the N residual effect. The last approach would have the theoretical advantage that the crop following
the green manure crop, here: potatoes, which might benefit more from the N in the green manure
residues would also bear a higher share of the burden. However, the disadvantage is that exact numbers of
the residual effect are needed and those would differ from study to study and increase the uncertainty. Furthermore,
the beneficial residual effect is not only caused by N but also carbon (C) with an increased soil
carbon level, which affects all of the crops in the crop rotation equally. Therefore, we recommend dividing
the environmental burdens and benefits from these green manure and catch crops equally on the hectares
used for sales crops in the crop rotation.
The study shows that both the carbon footprint results based on the full crop rotation and the results for
the specific crops would had been very different if the environmental burden from the green manure and
catch crops and the soil carbon changes had not been included.
5. Conclusion
In conclusion, the study highlights the importance of analysing the whole crop rotation and including soil
carbon changes when estimating carbon footprints of organic crops especially where green manure crops are
included. Two methods were presented, which enable an integration of green manure crops and catch crops
in the overall analysis. The analysis over the whole rotation should be used to judge on different rotation
designs. In order to calculate carbon footprint values for the specific crops, it is recommended to include the
environmental impacts from green manure and catch crops equally on the hectares used for sales crops in the
crop rotation.
6. References
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