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

PARALLEL SESSION 5B: METHODOLOGICAL CHALLENGES FOR CROP PRODUCTION SYSTEMS 8 th Int. Conference on
LCA in the
Agri-Food Sector, 1-4 Oct 2012
Winter field pea (Pisum sativum L.) cv. Lucy, and winter wheat (Triticum aestivum L.) cv. Cézanne, were
sown as sole crops at 80 and 260 pl m −2 , respectively. Winter pea-wheat intercrops (IC) were grown in a
substitutive design, each species being sown at half its sole crop density, both species being mixed within the
rows. All the experiments were arranged in randomized complete block designs with three replicates. The
soil was a clayey sandy loam (27.7% clay, 42.1% silt, 27.8% sand).
2.2. Crop management and analytical methods
In all experiments, pests were controlled with pesticides when required. No irrigation was provided. Inorganic
soil N, measured in February (end of winter), varied from 55 to 60 kg N ha −1 in the 0–90 cm soil layer.
N was applied as NH4NO3 as liquid fertiliser (Table 1). The fertiliser was enriched with 15 N (δ 15 N= 200‰) in
order to follow the dynamics of the amount of nitrogen derived from air (Ndfa) and accumulated in pea
shoots. Pea sole crops were always grown without applied N. For other details on methods concerning field
experiment, see Naudin et al., (2010).
Table 1. Treatments, N fertilisation, mean grain yields and mean LER.
Crop
design
Treatments Treatments in
Naudin et al. (2010)
Time of
N-fertilization
Rate of
N-fertilization
(kg N ha -1 )
Wheat GY
(g.m - ²)
Pea GY
(g.m - ²)
LERw LERp LER
SC P100 N0 B-Psc N0 — 0 — 397 (±51) — — —
SC W100 N B-Wsc N 07/03; 20/03; 14/05 80; 70; 40 857 (±36) — — — —
IC P50W50 N0 B-IC N0 — 0 275 (±48) 417 (±60) 0.32 (±0.05) 1.11(±0.26) 1.43 (±0.22)
IC P50W50 N B-IC4 07/03 45 413 (±60) 335 (±31) 0.48 (±0.06) 0.89 (±0.18) 1.37 (±0.12)
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). 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 Nfertilised
intercrops), or not (“N0”). LERw: partial land equivalent ratio for wheat. LERp: partial land equivalent ratio for pea. Values for grain yields
are means (n=3)±SE (Standard Errors)
2.3. LCA
2.3.1. Evaluation methodology.
Potential impacts were estimated according to LCA methodology, from soil tillage for sowing to harvest
(including the grain sorting process). The functional unit is 1 kg of wheat grain of bread making quality.
Direct emissions were estimated based on the field experiment and International Panel on Climate Change
(IPCC) 2006 recommendations. Indirect emissions were estimated with the help of the Ecoinvent 2007 database,
version 2.0 (Nemecek and Kägi, 2007). The production of seed for sowing was taken into account: we
assumed that inputs required for seed production were similar to those required for the corresponding crop.
2.3.2. Calculation of emissions.
Emissions to air were estimated for NH3, N2O and NOx. Emission factors for NH3 volatilisation following
application of mineral fertiliser were based on Nemecek and Kägi (2007). Emission factors for N2O were
based on IPCC (2006), and emissions of NOx were estimated according to Nemecek and Kägi (2007) at 21%
of emissions of N2O. Losses of NO3 - to groundwater were estimated from experimental measurements.
Phosphate emissions to water were estimated according to Nemecek and Kägi (2007) considering leaching to
groundwater and run-off to surface water for soluble phosphate, as well as erosion of soil particles containing
phosphorus.
2.3.3. Characterisation factors.
The following impact categories were considered: climate change (CC) (corresponding to greenhouse gas
emissions, kg CO2 eq.), eutrophication (EU) (g PO4
467
3- eq.), and cumulative energy demand (CED) (MJ eq.).
The indicator result for each impact category was determined by multiplying the aggregated resources used
and the aggregated emissions of each individual substance with a characterisation factor for each impact
category to which it may potentially contribute.
Climate change and eutrophication were calculated using the CML2 ‘baseline’ and ‘all categories’ 2001
characterisation methods as implemented in the Ecoinvent v2.0 database. Cumulative energy demand (CED)
was calculated according to its version 1.05 as implemented in the Ecoinvent v2.0 database. For climate
change, we updated values of characterisation factors (Forster et al., 2007) for biogenic methane (new value
25 kg CO2 eq.) and nitrous oxide (new value 298 kg CO2 eq.). A description of the CML 2001 and CED
methods can be found in Frischknecht et al., (2007).