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
Figure 2. Potential impacts of 1 ha of pea-wheat intercrops relative to combinations of respective sole crops
on a basis of equivalence of cropped area or of equivalence of production (including impacts of the grain
sorting process). W100: wheat sole crop. P100: pea sole crop. P50W50: substitutive intercrops of pea and
wheat (“50” indicates half of the recommended plant density when sole cropped). IC: intercrop. SC: sole
crop. Crops are N-fertilised (“N”: 190 kg N ha -1 on sole cropped wheat, and 45 kg N ha -1 at the beginning of
stem elongation on N-fertilised intercrops), or not (“N0”). Values are means (n=3)±SE (Standard Errors).
4. Discussion
Concerning sole cropped wheat, estimated impacts for CC and CED were in accordance with previous results
(Mosnier et al., 2011). Our estimated impacts for EU were lower than those exhibited by Mosnier et al.,
(2011) (1.17 and 3.8 g PO4 3- eq., respectively). Mosnier et al., (2011) calculated mean values for France.
Therefore, differences may result from the specific soil N dynamics in our experiments.
ICs allowed producing wheat with lower impacts than sole cropped wheat, whatever the allocation
method (reduction was at least -20%; fig. 1). However, allocation method strongly affected results. The system
expansion method did produce surprising results, as shown by negative impacts for wheat from unfertilised
ICs. In our study, data used for system expansion was solid, as we estimated impacts for IC pea
from the impacts associated with the production of the same quantity and quality of SC pea grains. Indeed,
previous results have shown that sole cropped pea grains are of the same quality than those from intercrops
(Naudin et al., 2010). In fact, inconsistent results may be explained by interspecific complementarity which
allows a better efficiency in resource use but was not taken into account in the system expansion approach.
Our proposition was to avoid allocations or system expansion by assessing impacts of ICs from those of SCs.
Indeed, wheat and pea grains from ICs are of the same quality as those from sole cropping (Naudin et al.,
2010), and introduction of ICs in cropping systems is to be considered as a substitution for a combination of
both SC wheat and SC pea. Two comparisons were proposed: i) equivalence of area; and ii) equivalence of
production (Fig. 2). The originality of this proposition is the introduction in LCA of approaches linked with
two indicators currently used for assessing the performances of a multispecific canopy: net biodiversity effect
(Loreau and Hector, 2001), and LER (de Wit and Van den Bergh, 1965). Indeed, the net biodiversity
effect analyses production of biomass on the basis of an equivalence of area, and the LER on the basis of
equivalence of production.
Using these ways of comparison, results showed that ICs always decreased impacts compared to SCs
(from -13% to -54%). Finally, our proposition involves redefining our functional unit and estimating impacts
for a mix of wheat and pea grains (including grain sorting).
5. Acknowledgment
We gratefully acknowledge the technical staff of LEVA (Laboratoire d’Ecophysiologie Végétale et
Agroécologie), and of the experimental station of La Jaillière (ARVALIS Institut du Végétal) for their excellent
technical assistance. This work was jointly founded by ADEME (Agence de l’Environnement et de la
Maîtrise de l’Énergie), CASDAR n° 431 and n° 8058 (Compte d’Affectation Spéciale pour le Développement
Agricole et Rural), Conseil Général of Maine-et-Loire, UNIP (Union National Interprofessionnel des
plantes riches en Protéines), and FESIA (DIVeRE research program).
470
20
18
16
14
12
10
8
6
4
2
0
Climate Change (t CO CO2 2 eq)
3-
Eutrophication (kg PO4--- PO4 eq) eq)
Total Cumulative Energy Demand (GJ eq)
Equivalence
of cropped area
P50W50 N0 P50W50 N Mean of SCs (P50W50 N0)eq (P50W50 N)eq
(IC on 1ha) (IC on 1ha) (0.5ha of W100 N
+ 0.5ha of P100 N0)
Equivalence of production
compared to IC
(combination of SCs;
0.32ha of W100 N
+ 1.11ha of P100 N0)
(combination of SCs;
0.48ha of W100 N
+ 0.89ha of P100 N0)