Wave energy dissipation by vegetation in TOMAWAC

Water Qualit

Environmental assessment of biofuel pathways in Ile de France based on ecosystem modelling, including land-use change effects

International audienceThe greenhouse gas (GHG) balance of biofuels largely hinges on the magnitude of nitrous oxide (N2O) emissions from arable soils during feedstock production, which are highly variable. Here, used an agro-ecosystem model to generate these emissions at a high resolution over the Ile-de-France region in Northern France, for a range of feedstocks. The emissions were input to a life-cycle assessment of candidate biofuel pathways: bioethanol from wheat and sugar-beet, biodiesel from oilseed rape, and ethanol from miscanthus. Compared to the widely-used methodology based on fixed emission factors, ecosystem modelling lead to 55% to 70% lower estimates for N2O emissions, emphasizing the importance of regional factors. The life-cycle GHG emissions of 1st generation biofuels were 50% to 70% lower than fossile-based equivalents, and 85% lower for cellulosic ethanol. Indirect land-use change effects negated these savings for bio-diesel and wheat ethanol, but were offset by direct effects for cellulosic ethanol

Variations in Chlorella lipid content in commercial and in-lab produced biomass☆

Microalgae appear as a sustainable source of biomass with relevant nutritional qualities. Still, regulatory restrictions currently limit the use of eukaryotic microalgae for human consumption to a short list of species dominated by Chlorella spp. Chlorella biomass contains valuable proteins but also interesting lipids, including polyunsaturated fatty acids (PUFA) ω3 and ω6. The amount of PUFA and the ω6/ω3 ratio vary significantly depending on the species and cultivation trophic mode. While the lipid profils of in-lab produced Chlorella has been widely studied, the variability of lipid content in commercial biomasses is barely described. Here, lipid classes and fatty acid profiles of six commercial biomasses of Chlorella spp. as well as those of lab-produced C. sorokiniana grown in photo-autotrophy and in four mixotrophy conditions were characterized. Results showed significant lipid composition variations between the biomasses, such as the triacylglycerols/glycolipids and ω6/ω3 contents. The ω6/ω3 ratios were lower in photo-autotrophic mode (2.5) while they ranged between 1.3 and 8.9 in commercial biomasses. The free fatty acids level was also variable (1.4% to 17.9% of total lipids). As a consequence, Chlorella lipid content and quality differed significantly, impacting the potential nutritional benefits of the consumption of commercial biomass. Processing and post-processing conditions should therefore be carefully controlled to optimize lipid profiles

IMproved Assessment of the Greenhouse gas balance of bioeNErgy pathways (IMAGINE)

Rapport de projetControversy is brewing about the potential greenhouse gas (GHG) savings resulting from the displacement of fossil energy sources by bioenergy, which mostly hinges on the uncertainty on the magnitude of nitrous oxide (N2O) emissions from arable soils occuring during feedstock production. The life-cycle GHG budget of bioenergy pathways are indeed strongly conditioned by these emissions, which are related to fertilizer nitrogen input rates but largely controlled by soil and climate factors. The IMAGINE project, funded by by the ENERBIO/Tuck Foundation from January 2010 to December 2011 aimed at improving the estimation of N2O emissions from local to regional scales using ecosystem models and measurements and modeling of atmospheric N2O in the greater Paris (France) basin. Ground fluxes of N2O were measured in two locations to assess the effect of soil type and management (in particular drainage), crop type (including lignocellulosics such as triticale, switchgrass and miscanthus), and climate on emission rates and dynamics. Atmospheric concentrations of N2O were monitored with high precision in 3 sites relevant to the Paris basin, using Radon tracing to produce source estimates. High-resolution maps of N2O emissions over France were simulated with a generic ecosystem model, O-CN, and an agro-ecosystem model, CERES-EGC, using geographical databases on soils, weather data, land-use and crop management. The models were tested against the ground flux measurements, and the emission maps were fed into the atmospheric chemistry-transport model CHIMERE. The maps were tested by comparing the CHIMERE simulations with time series of N2O concentrations measured at various heights in two locations in 2007. The emissions of N2O, as integrated at the regional scale, were used in a life-cycle assessment of representative biofuel pathways (bioethanol from wehat, sugar-beet and miscanthus; biodiesel from oilseed rape). Effects related to direct and indirect land-use changes (and their impact on soil carbon stocks) were also included in the assessment. The spatial distribution of the N2O emission generated with the O-CN and CERES-EGC ecosystem models differed markedly: O-CN simulated higher emissions in the west of France due to livestock farming whereas CERES-EGC emphasized the greater Paris basin with intensive cereal farming. This was partly due to variations in forcing such as N application rates, cropland area, and soil properties, but also to modelling concepts. In particular, the simulation of soil water balance and the response of N2O emissions to surface moisture follow different approaches in both models. On an annual basis, N2O emissions from agricultural soils over France totalled 17, 56 and 69 Gg N2O-N with the CERES-EGC, O-CN, and EDGAR32 maps, respectively. In both atmospheric measurement sites, simulations with the EDGAR32 map were closest to the observed concentrations, especially in spring when fertilizers are applied. This points to an underestimation by the ecosystem models by 20 to 80%, although both models compared well with measured ground fluxes in a few cropland test sites. Various causes for this pattern may be explored. First, indirect emissions via nitrate leaching were about half of the direct emissions according to the EDGAR database but were ignored by the ecosystem models. These may be easily introduced based on their simulations of nitrate leaching fluxes. Secondly, the regional inputs of mineral N-fertilizer were generally lower than fertilizer sales, by up to 50%, and this should be corrected. Lastly, models were mostly parameterized in sites with low N2O emissions rates, and should be tested in sites with higher emission potentials. The main results of the project may be summarized as follows: - an ambient air monitoring network was established for high accuracy N2O measurements, compatible with existing networks elsewhere in the world, in 3 sites in France; - high time resolved N2O surface concentrations were made available for two stations, along with estimates of N2O sources based on Rn-tracing over the 2 years of the project; ground fluxes were measured on arable crops in two locations (Orléans and Grignon), emphasizing the effect of rainfall patterns, drainage, fertilizer input rates and timing on N2O emissions. Measurements carried out over perennial lignocellulosic crops evidenced much smaller (up to an order of magnitude) N2O emission rates from these plants. two ecosystem models were improved and tested for the prediction of daily N2O emissions from agricultural and forest soils, resulting in prediction errors similar to the uncertainties in the observation erros. - simulated regional and global N2O emission maps are derived using a validated, process based N-cycle model implemented in the dynamic vegetation model; - The impact of higher model resolution is documented on simulated N2O mixing ratios with partitioning between the different emission sources; - A feasibility study for N2O inversions has been achieved; - A database contains the results open to the scientific community for further analysis; This report synthesizes the findings of the project, for each work-package, and closes with a tentative budget for N2O emissions in France in 2007 combining bottom-up and top-down estimates for the various sources (biogenic and non-biogenic)

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

Environmental assessment of biofuel chains based on ecosystem modelling, including land-use change effects

The potential greenhouse gas (GHG) savings resulting from the displacement of fossil energy sources by bioenergy mostly hinges on the uncertainty on the magnitude of nitrous oxide (N2O) emissions from arable soils occuring during feedstock production. These emissions are broadly related to fertilizer nitrogen input rates, but largely controlled by soil and climate factors which makes their estimation highly uncertain. Here, we set out to improve estimates of N2O emissions from bioenergy feedstocks by using ecosystem models and measurements and modeling of atmospheric N2O in the greater Paris (France) area. Ground fluxes were measured in two locations to assess the effect of soil type and management, crop type (including ligno- cellulosics such as triticale, switchgrass and miscanthus), and climate on N2O emission rates and dynamics. High-resolution maps of N2O emissions were generated over the Ile-de-France region (around Paris) with two ecosystem models using geographical databases on soils, weather data, land-use and crop management. The models were tested against ground flux measurements and the emission maps were fed into the atmospheric chemistry-transport model CHIMERE. The maps were tested by comparing the CHIMERE simulations with time series of N2O concentrations measured at various heights above the ground in two locations in 2007. The emissions of N2O, as integrated over the region, were used in a life-cycle assessment of representative biofuel pathways: bioethanol from wheat and sugar-beet (1st generation), and miscanthus (2nd generation chain); bio-diesel from oilseed rape. Effects related to direct and indirect land-use changes (in particular on soil carbon stocks) were also included in the assessment based on various land-use scenarios and literature references. The potential deployment of miscanthus was simulated by assuming it would be grown on the current sugar-beet growing area in Ile-de-France, or by converting land currently under permanent fallow. Compared to the standard methodology currently used in LCA, based on fixed emissions for N2O, the use of model-derived estimates leads to a 10 to 40% reduction in the overall life-cycle GHG emissions of biofuels. This emphasizes the importance of regional factors in the relationship between agricultural inputs and emissions (altogether with biomass yields) in the outcome of LCAs. When excluding indirect land-use change effects (iLUC), 1st generation pathways enabled GHG savings ranging from 50 to 73% compared to fossile-derived equivalents, while this figure reached 88% for 2nd generation bioethanol from miscanthus. Including iLUC reduced the savings to less than 5% for bio-diesel from rapeseed, 10 to 45% for 1st generation bioethanol and to 60% for miscanthus. These figures apply to the year 2007 and should be extended to a larger number of years, but the magnitude of N2O emissions was similar between 2007, 2008 and 2009 over the Ile de France region

Soil erosion has mixed effects on the environmental impacts of wheat production in a large, semi-arid Mediterranean agricultural basin

International audienceSoil erosion poses a significant threat to agricultural production worldwide, with a still-debated impact on the current increase in atmospheric CO2. Whether erosion acts as a net carbon (C) source or sink also depends on how it influences greenhouse gas (GHG) emissions via its impact on crop yield and nutrient loss. These effects on the environmental impacts of crops remain to be considered. To fill this gap, we combined watershed-scale erosion modeling with life cycle assessment to evaluate the influence of soil erosion on environmental impacts of wheat production in the Ebro River basin in Spain. This study is the very first to address the full GHG balance of erosion including its impact on soil fertility and its feedback on crop yields. Two scenarios were simulated from 1860 to 2005: an eroded basin involving conventional agricultural practices, and a non-eroded basin involving conservation practices such as no-till. Life cycle assessment followed a cradle-to-farm-gate approach with a focus on recent decades (1985–2005). The mean simulated soil erosion of the eroded basin was 2.6 t ha−1 year−1 compared to the non-eroded basin. Simulated soils in both eroded and non-eroded basins lost organic C over time, with the former emitting an additional 55 kg CO2 ha−1 year−1. This net C source represented only 3% of the overall life cycle GHG emissions of wheat grain, while the emissions related to the increase of fertilizer inputs to compensate for N and P losses contributed a similar percentage. Wheat yield was the most influential parameter, being up to 61% higher when implementing conservation practices. Even at the basin scale, erosion did not emerge as a net C sink and increased GHG emissions of wheat by 7–70%. Nonetheless, controlling erosion through soil conservation practices is strongly recommended to preserve soils, increase crop yields, and mitigate GHG emissions

Variations in Chlorella spp. lipid content in commercial and in-lab produced biomasses

International audienceMicroalgae appear as a sustainable source of biomass with valuable nutritional qualities. Under the current regulations, very few biomasses of eukaryotic microalgae species are allowed for human food and mostly belong to the Chlorella genus. Chlorella biomass can contain lipids of interest such as polyunsaturated fatty acids (PUFA) ω3 and ω6. Yet, the amount of PUFA as well as the ω6/ω3 ratio can vary significantly depending on the species considered as well as the trophic mode used for cultivation (photo-autotrophy, mixotrophy or heterotrophy). While the lipid content of in-lab produced Chlorella has been extensively studied, the variability of commercial biomass composition is barely described (Canelli et al., 2020). Here we characterized the lipid classes (TAG : triacyclglycerols; FFA: free fatty acids; MGDG: monogalactosyldiacylglycerols; DGDG: digalactosyldiacylglycerols; PE: phosphatidylethanolamines; PC: phosphatidylcholines; SQDG: sulfoquinovosyldiacylglycerols) and fatty acid profiles of commercial biomasses of different Chlorella spp. as well as those of in lab-produced Chlorella sorokiniana, grown in photo-autotrophy and mixotrophy conditions