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
Greenhouse gas emissions
(g CO2 eq. kg-1 crop DM)
500
400
300
200
100
0
Mulching No input Slurry Conventional
Figure 3. Carbon footprints per kg sales crop DM at farm gate based on the full crop rotations 2006-8. The
values are the means over the three years ± S.E.
The analysis of the individual crops provided a specific carbon footprint value of e.g. spring barley grown
in the different crop rotations (Figure 4). Figure 4 shows that the carbon footprint values for e.g. spring barley
grown in the ‘Mulching’ rotation was affected by the soil carbon sequestration and the N2O emissions
caused by the green manure crop compared to the ‘Slurry’ or ‘Conventional’ rotations. These findings show
that the contributions caused by the green manure crop to the carbon footprint of the organic crops are considerable.
Mulching
No input
Slurry
Conventional
-400 -200 0 200 400 600
SPRING BARLEY
2006-2008
Manure input
N2O, main crop
N2O, grass-clover
N2O, catch crop
Diesel and machinery, main crop
Diesel and machinery, grass clover
Soil C change
Greenhouse gas emissions per kg spring barley
(g CO2 eq. kg
Figure 4. Carbon footprints of spring barley at farm gate in the different crop rotations 2006-8. The values
are the means over the three locations and three years (2006-8).
-1 spring barley)
4. Discussion
When calculating the carbon footprint of crops from crop rotations where green manure crops or catch
crops are included, there is a need to include the environmental burdens and benefits from the green manure
or catch crops and thus include the full crop rotation in the assessment.
One solution, as suggested here, is to assess the full crop rotation as a ‘black box’ based on kg sales crop
DM from the different crops. The analysis over the whole rotation can be used to judge on different rotation
designs. The evaluation could be based on kg DM, as suggested here or be related to the functions of agriculture
as discussed by Nemecek et al., (2011). Another option is to use a functional unit that reflects the dietary
needs by humans as discussed by Smedman et al., (2010).
However, there is a need for carbon footprint values for the specific crops. Furthermore, the full crop rotation
implies several crop specific inputs and several outputs i.e. different sales crops from the rotation,
371