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
466
LCA applied to pea-wheat intercrops: the significance of allocation
Christophe Naudin 1* , Hayo van der Werf 2,3 , Marie-Hélène Jeuffroy 4 , Guénaëlle Corre-Hellou 1
1 LUNAM Université, Groupe ESA, UR LEVA - SFR 4207 QUASAV, 55 rue Rabelais, 49007 Angers cedex 01, France
2 INRA, UMR1069 Sol, Agro and hydroSystem, 35000 Rennes, France
3 Agrocampus Ouest, 35000 Rennes, France
4 UMR Agronomie INRA-AgroParisTech, Bâtiment EGER, 78850 Thiverval-Grignon, France
Corresponding author. E-mail: c.naudin@groupe-esa.com
ABSTRACT
Cereal-legume intercrops (ICs) are a promising way to combine high productivity and several ecological benefits in temperate agroecosystems.
This study aims to apply LCA to ICs by (i) testing several methods of allocation, or system expansion; (ii) in order to
assess the environmental impacts of the co-products.
Agronomic performances of winter pea-wheat IC, sole-cropped (SC) pea and wheat were assessed in field experiments in France.
LCA was carried out from sowing to harvest, including grain sorting. Functional unit is 1 kg of wheat grain (bread making quality).
ICs allowed producing wheat with lower impacts than SC wheat (at least -20%). Allocation method strongly affected results and
system expansion was shown to be inappropriate, as it did not take into account benefits from interspecific complementarity. Then
we redefined our functional unit to assess impacts of ICs from those of SCs (equivalence of area, or of production). ICs always decreased
impacts compared to SCs (from -13% to -54%).
Keywords: system expansion; cereal; legumes; environmental impacts
1. Introduction
During recent decades, it has become obvious that the design of cropping systems has to take into account
the environmental impacts of agricultural practices (Altieri, 1989) in order to limit the use of non-renewable
natural resources and chemical inputs and to improve their efficiency (Tilman et al., 2002).
Intercropping is the simultaneous growing of two or more species in the same field, with variations in the
species used, the densities of each species and their spatial arrangements (Willey, 1979). Apart from its frequent
use in pastures, this practice is not very widespread in temperate agroecosystems. However cereallegume
intercrops are gaining interest in Europe due to the increasing awareness of environmental damage
arising from the intensive use of fertilisers and pesticides and the increasing cost of these inputs (Anil et al.,
1998). Moreover, intercrops are mainly widespread in organic farming but may have interesting potential
uses in conventional farming systems, in particular for the development of low-input multi-use crops.
Intercropping is known to increase yields, yield stability and grain N concentration of the cereal, and to decrease
weed pressure and N leaching. Indeed, cereal-legume intercropping has been demonstrated to be an
interesting way to improve the nitrogen efficiency of agroecosystems (Hauggaard-Nielsen et al., 2009) and
limit losses to the environment. These advantages are assumed to be mainly linked to the complementary
use, in time and space, of N sources by the different components of the intercrop (Corre-Hellou et al., 2006;
Jensen, 1996; Naudin et al., 2010). Thus intercrops can contribute to the development of cropping systems
which combine high productivity and several ecological benefits. However, few studies have attempted to
assess environmental benefits based on multicriteria approaches (Pelzer et al., 2012), and, to our knowledge,
none using life cycle assessment (LCA).
LCA is a method to assess impacts of a product considering all stages of its life cycle. This methodology,
so called “from cradle to grave”, assesses resource use and emissions to the environment, from the extraction
of resources, through each step of the production process, including product parts and recycling or final disposal
(Guinée et al., 2002). In the case of product systems yielding several co-products, impacts have to be
allocated among the co-products. This is the case for cereal-legume IC, and the estimated impacts of the coproducts
may well be dependent on the choice of the impact allocation method (Ekval and Finnveden, 2001;
Heijungs and Guinée, 2007).
The aim of this study was to apply LCA to ICs by (i) testing several methods of impact allocation (mass,
economic, based on N yield in grains) or avoided allocation by system expansion (ii) in order to assess the
environmental impacts of the co-products.
2. Methods
2.1. General design of experiments
Field experiments were carried out in France in 2007–2008 at La Jaillière (see Exp B in Naudin et al.,
2010) at the experimental station of ARVALIS Institut du Végétal, in western France (47°26’N, 0°58’W).