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

PARALLEL SESSION 4C: CROP PRODUCTION SYSTEMS 8 th Int. Conference on LCA in the
Agri-Food Sector, 1-4 Oct 2012
Crop protection showed relatively low contributions to the impact variability compared to other cropping
system components. This result is not due to a low impact of pesticides, since normalised results (not
shown) pointed terrestrial ecotoxicity (TET) as second important impact. The main reason why crop protection
was not discriminating is that all pesticides emissions were emitted into the soil as recommended by
(Nemecek and Kägi 2007).This method does not consider the behaviour of pesticides in the environment in
relation to application methods, and subsequent transports in the main environmental compartments. As a
consequence, the main drivers were pesticide application rates and toxicity potentials. Considering these
drivers, the use of cypermethrin and organo phosphorus compounds (terbufos and dimethoate) were clearly
discriminating the systems’ impact, the first one due to its high application rate, the two other ones for their
high toxicity. The assessment of crop protection practices requires improved methods for the estimation of
pesticide emissions to the different environmental compartments as it should be a hot-spot for tropical crops.
Fertilisation practices contributed to differentiating intensive cropping systems from extensive ones, mainly
based on fertiliser types and rates. However, intensive fertilisation practices did not correlate with greater
yields. This observation led us to question the methods used to estimate field emissions. Crop uptake is the
main sink for applied nutrients. If it varies, field emissions should vary accordingly, especially for nitrate
leaching which is related to the amount of nitrogen available in soils during drainage events. We could not
use a method based on nitrogen balance for nitrate leaching since it requires to estimate drainage events
(Brentrup et al., 2000), which depended in our cropping systems on the timing of irrigation inputs. No methods
in LCI guidelines allowed including effect of irrigation practices on nitrate emissions. In addition, for
cropping system with no drainage events (low water supplied per irrigation event), there should be an accumulation
of nitrogen in soil. This might involve higher emissions of nitrous and nitric oxides than the average
factor proposed by IPCC (IPCC 2006) and would deserve an improved modelling as well. For tropical
horticultural systems where yields can be significantly reduced due to pest pressure, the behaviour of nitrogen
in the environment needs to be modelled considering irrigation practices, the timing and method of fertiliser
application and the actual yield.
5. Conclusion
The proposed typology allows the identification of representative individual fields to assess the environmental
impact of tomato cropping systems in Benin. Our approach identified key data to be collected and
estimated accurately in the LCI for horticultural products in the Tropics. In a near future we are planning to
include these data in our LCI to assess their effects on LCA results in terms of sensitivity and uncertainty.
Identifying cropping system types and specific LCI data makes it possible to reveal site-specific differences
in the LCA results which did not appear when using the recommended LCI data set. Although LCA claims to
be a method assessing global environmental impacts, we believe that results should account for key local
variables.
6. References
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Brentrup F, Küsters J, Lammel J, Kuhlmann H (2000) Methods to estimate on-field nitrogen emissions from crop production as an
input to LCA studies in the agricultural sector. Int J Life Cycle Ass (6):349-357.
Chabalier PF, Van de Kerchove V, Saint Macary H (2006) Guide de la fertilisation organique à la Réunion. CIRAD.
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IPCC (2006) Chapter 11: N2O emissions from managed soils, and CO2 emissions from lime and urea application. In: Eggleston S,
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Environmental Strategies, Hayama, Japan.
Martínez-Blanco J, Muñoz P, Antón A, Rieradevall J (2011) Assessment of tomato Mediterranean production in open-field and
standard multi-tunnel greenhouse, with compost or mineral fertilizers, from an agricultural and environmental standpoint. J
Clean Prod (9-10):985-997.
Nemecek T, Kägi T (2007) Life Cycle Inventories of Agricultural Production Systems. Final report ecoinvent, vol v2.0 No.15. Swiss
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farms and production units: An example from Tunisia. Agricultural Water Management (8):973-983.
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