Using a crop model to account for the effects of local factors on the LCA of sugar beet ethanol in Picardy region, France

CT1 ; CT3 ; EnjS1 ; EnjS4 ; Base de données AgroclimInternational audienceThe results of published Life Cycle Assessments (LCAs) of biofuels are characterized by a large variability, arising from the diversity of both biofuel chains and the methodologies used to estimate inventory data. Here, we suggest that the best option to maximize the accuracy of biofuel LCA is to produce local results taking into account the local soil, climatic and agricultural management factors. Methods We focused on a case study involving the production of first-generation ethanol from sugar beet in the Picardy region in Northern France. To account for local factors, we first defined three climatic patterns according to rainfall from a 20-year series of weather data. We subsequently defined two crop rotations with sugar beet as a break crop, corresponding to current practice and an optimized management scenario, respectively. The six combinations of climate types and rotations were run with the process-based model CERES-EGC to estimate crop yields and environmental emissions. We completed the data inventory and compiled the impact assessments using Simapro v.7.1 and Ecoinvent database v2.0. Results Overall, sugar beet ethanol had lower impacts than gasoline for the abiotic depletion, global warming, ozone layer depletion and photochemical oxidation categories. In particular, it emitted between 28 % and 42 % less greenhouse gases than gasoline. Conversely, sugar beet ethanol had higher impacts than gasoline for acidification and eutrophication due to losses of reactive nitrogen in the arable field. Thus, LCA results were highly sensitive to changes in local conditions and management factors. As a result, an average impact figures for a given biofuel chain at regional or national scales may only be indicative within a large uncertainty band. Conclusions Although the crop model made it possible to take local factors into account in the life-cycle inventory, best management practices that achieved high yields while reducing environmental impacts could not be identified. Further modelling developments are necessary to better account for the effects of management practices, in particular regarding the benefits of fertiliser incorporation into the topsoil in terms of nitrogen losses abatement. Supplementary data and modelling developments also are needed to better estimate the emissions of pesticides and heavy metals in the field

Modeling of nitric oxide emissions from temperate agricultural ecosystems.

48 p.Arable soils are a significant source of nitric oxide (NO), most of which is derived from nitrogen fertilizers. Precise estimates of NO emissions from these soils are thus essential to devise strategies to mitigate the impact of agriculture on tropospheric ozone regulation. This paper presents the implementation of a soil NO emissions submodel within the environmentally-orientated soil crop model, CERES-EGC. The submodel simulates the NO production via nitrification pathway, as modulated by soil environmental drivers. The resulting model was tested with data from 4 field experiments on wheat- and maize-cropped soils representative of two agricultural regions of France, and for three years encompassing various climatic conditions. Overall, the model gave correct predictions of NO emissions, but shortcomings arose from an inadequate vertical distribution of fertilizer N in the soil surface. Inclusion of a 2-cm thick topsoil layer in an 'micro-layer' version of CERES-EGC gave more realistic simulations of NO emissions and of the under-lying microbiological process. From a statistical point, both versions of the model achieved a similar fit to the experimental data, with respectively a MD and a RMSE ranging from 1.8 to 6.2 g N-NO ha−1 d−1, and from 22.8 to 25.2 g N-NO ha−1 d −1 across the 4 experiments. The cumulative NO losses represented 1 to 2% of NH+4 fertilizer applied for the maize crops, and about 1% for the wheat crops. The 'micro-layer' version may be used for spatialized inventories of biogenic NO emissions to point mitigation strategies and to improve air quality prediction in chemistry transport models

Environmental impact of the substitution of imported soybean meal with locally-produced rapeseed meal in dairy cow feed

35 pages, 4 figures, 2 tables, Supplementary materialsInternational audienceGrowing public concerns about the traceability, safety and environmental-friendliness of food products provide an incentive for shorter supply chains in agricultural production. Here, we assessed the environmental impacts of the substitution of imported soybean meal with locally-produced rapeseed meal in French dairy production systems, using a life-cycle approach. Two feeding rations based on either French-produced rapeseed meal or Brazilian-produced soy meal as concentrates, were compared for nine impact categories, including global warming, ecotoxicity and eutrophication. Crop production was the main contributor to most impacts, while overseas transport of soy meal only had a marginal effect. The "Soybean" ration appeared more environmentally efficient than the "Rapeseed" ration because it involved less intensive management practices, in particular regarding synthetic fertilizers consumption. However, land-use changes brought about by soybean cultivation should also be examined

Well to wheels analysis of biofuels vs. conventional fossil fuels : a proposal for greenhouse gases and energy savings accounting in the French context

SAE Technical Paper no 2008-01-0673The recent development of biofuel production worldwide is closely linked to GHG savings objectives and to regional agricultural policies. Many existing studies intend to evaluate the net non renewable energy and GHG savings associated to the various biofuel production pathways. However, there is no consensus on the results of those studies. The main explanations of variations among the results are the following : - energy consumption and GHG emissions of the reference fossil pathway, - data used for the representation of farming processes and biofuel production processes, - accounting for carbon storage in agricultural soils, - reference use of the land, - choice of an allocation method in case of coproduction. There is a strong drive in the European Union for a certification on the sustainability of biofuel pathways. Germany, The Netherlands, The United Kingdom and France have started to work on reference framework for the evaluation of biofuel pathways, in particular (but not only) from the GHG emissions point of view. This study intends to detail a WTW assessment for first generation biofuels in the French context. A detailed description of today French agriculture and biofuel production is made in order to give reference data for the WTW analysis. Based on the existing biofuel pathways and their possible evolution, this study then evaluates the potential GHG savings according to the French objectives of biofuel use: 5.75% in 2008 and 7% in 2010. The sensitivity of the results to regional factors (mainly in the farming processes) is then calculated in order to evaluate the possible variations. Effect of land use change is not taken into account in that study. The question of a national reference value is raised: in a certification process, is it possible to use one only reference value for GHG savings, or do we need more detailed references

Generating high-resolution inventories of N2O emissions from agricultural soils with an agro-ecosystem model

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Multivariate sensitivity analysis for complex dynamic models with random factors

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Sensitivity analysis for complex dynamic models: A global sensitivity index per factor

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