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International audience; Sorghum, a perennial C4 warm-season grass is among the foremost herbaceous species being advanced as a source of biomass for energy but also for biobased materials production. However, expansion of these value chains is currently hampered by a lack of knowledge regarding the relationships of the sorghum stem biological properties and the end use product properties. Two main application sectors have been chosen for sorghum biomass valorisation in the Biomass For the Future project (BFF) funded by the French research agency project:1) the use of lignocellulosic sorghum material in polymeric matrix composites and 2) the use of sorghum as a feedstock for methane production by anaerobic digestion ( a very dynamic sector in Europe : France Germany…).Plant biomass is chiefly composed of cell wall (a supra molecular arrangement of 3 macromolecules cellulose, hemicellulose and lignin) whose thickness and composition vary depending on the tissues type and anatomical traits. Thus the quality of the biomass and the performances of the industrial products resulting from the transformation of the biomass should depend directly on its histochemical composition. In this context, a panel encompassing the stem biochemical diversity of sorghum has been analyzed for their end-use product properties and also for their stem anatomy. As far as biocomposite sorghum based products were considered, their tensile strength, deformation at break, Young’s Modulus, resistance to impact and degree of darkening of the composites due to thermal degradation were analyzed. For methane production the biomethane potential (BMP) was assessed.These end-products properties were compared to the histochemical properties or the raw stem material. A high throughput histochemical phenotyping pipeline was developed in combination with NIRS biochemical predictions.We underline in this study the relationships between stalk related traits and ends use product properties. Our data clearly show how anatomical and histochemical traits can influence the potential methane production, the mechanical properties of the composites and, emphasize the key potential of the genotypic variability available in sorghum to develop varieties fitting the expectations of the different value chains.

International audience

To face global warming and fossil fuel depletion crisis, plant biomass will provide a renewable source of energy, materials and chemicals. Accordingly, agriculture will have to adapt not only to avoid competition between food-feed and non-food non-feed uses but also to ensure the economical and environmental sustainability of these productions. In this context, we are developing an integrative strategy merging genetics, breeding, material sciences, energy production, animal nutrition and socio economic analyses to accelerate the development of multipurpose sorghum value chains for both Mediterranean and tropical semi-arid conditions (West Africa). As a first step, new products (biocomposites) and uses (biomethane production) are being developed. Then the plant traits impacting the production and quality of the different end-products and uses are being identified taking advantage of the genetic diversity of sorghum. As a third step, the set-up of these key traits in the plant is being analyzed in order to describe their patterns of development / accumulation, their susceptibility to environmental constraints and provide some insights regarding their molecular determinism. Taking advantage of these functional information, the genomic regions impacting the key traits are being deciphered and used to develop new breeding tools and breeding strategies. In parallel, to maximize the probability to convert scientific results in local impacts, the different stakeholders of the value chains are being mobilized and territorial analyses aiming to assess the relevance of the different value chains are performed.

International audience

Sorghum is among the world's most important cereals in terms of human and animal nutrition. It is also currently identified as a promising crop to support the emerging bio-economy value chains that include energy production, biomaterials and molecules for food-feed and non-food-feed applications. In this context, the development of varieties adapted to the different end-uses is critical to provide the industries with relevant feedstock. Breeding sorghum for existing and emerging markets requires several steps, from the definition of “Industrial Ideotypes” down to the identification of “Molecular Ideotypes” in order to speed up the breeding process and optimize the genetic gains per unit of time. Firstly, expectations of the industrials in terms of composition and properties of the sorghum biomass for the different applications (“Industrial ideotypes”) have to be defined. Secondly, “Industrial ideotypes” have to be translated in “Biological ideotypes” which refers to the properties of the raw sorghum material in terms of composition and structure. Third, high-throughput phenotyping tools compatibles with genetic analyses and breeding constraints have to be developed. Fourth, strategies to disentangle the genetic determinism of the “Biological Ideotypes” have to be set up. And fifth, relevant breeding schemes able to provide new hybrids and relevant parents have to be initiated. We will illustrate this process through two examples related to the production of sorghum biocomposites and the optimization of sorghum biogas production. For both targets, we will show how, through the use of the sorghum genetic diversity, traits affecting the final product properties were identified. We will then illustrate the efforts that are currently developed to tackle the challenges linked to high-throughput phenotyping. We will finally show how these phenotyping tools are used on diverse association panels and multiparental designs to identify the genomic regions affecting the traits of interest and develop new hybrids and elite parents. Funding acknowledgement: This research is supported through the Biomass For the Future project (funded by ANR) and the BIOSORG project supported by the Agropolis (Labex Agro) and Cariplo foundations.

This work aims to investigate the impact of artificial and natural weathering on the end of life of polylactic acid and flax fiber reinforced polylactic acid composite. The studied end-of-life scenarios are reprocessing, composting and incineration. Numerous characterization test results lead to understand the degradation behaviors involved through weathering and end-oflife treatments.

Nowadays, biocomposite materials are booming and will be a growing end-of-life issue for the future. They are based on a thermoplastic matrix (oil-based or bio-based) reinforced with vegetable fillers or fibers. Consequently, the study of their end of life through recycling, composting and incineration is a scientific and technologic challenge.The first goal of this thesis is to study the reprocessing end of life (successive injection and grinding cycles) of polypropylene (PP) based biocomposites filled with wood flour. The impact of the wood particle size and a coupling agent was assessed. Thus, a very good mechanical stability was observed up to 7 reprocessing cycles despite some degradation from the material components. Then, the reprocessing after artificial or natural UV weathering was carried out. The major trend is a “regeneration” phenomenon of mechanical properties after reprocessing in spite of strong degradations after UV weathering. Moreover, the addition of wood filler tends to restrain the PP photochemical degradation.The second goal is to study the end of life of polylactic acid (PLA) based biocomposites reinforced with flax fibers. The impact of the composition, the processing technic and humidity weathering on the reprocessing was assessed. Similar “regeneration” phenomena were observed leading to conclude to the beneficial effect of reprocessing. Then composting and biodegradation aspects were investigated. Heat release rate measurements enabled to estimate the incineration potential which could be linked to the PLA degradation rate.; Les matériaux biocomposites, en particulier les composites matrice thermoplastique biosourcée ou non renforcée de charges ou de fibres végétales, connaissent actuellement un essor significatif et présentent pour l'avenir un gisement grandissant de matières en fin de vie. En conséquence, l'étude du comportement de ces matériaux au regard de différents scénarios de fin de vie que sont le recyclage mécanique, le compostage et l'incinération constitue un enjeu scientifique et technologique important. Le premier objectif de cette thèse est d'étudier la fin de vie par retransformation (cycles successifs d'injection et de broyage) de biocomposites à matrice polypropylène (PP) chargé de farine de bois. L'impact de la taille des particules de bois et d'un agent de couplage a été évalué. Une très bonne stabilité mécanique jusqu'à 7 cycles de retransformation a été observée malgré des dégradations des différents composants du matériau. Le comportement face à la retransformation après vieillissement artificiel accéléré ou après une exposition naturelle en extérieur a été étudié. La tendance majeure dégagée est un phénomène de « régénération » des propriétés mécaniques par retransformation, et cela malgré des dégradations importantes après vieillissement. Il a été également été observé que l'ajout de bois a tendance à limiter la photodégradation du PP. Le second objectif est d'étudier la fin de vie de biocomposites à matrice acide polylactique (PLA) renforcé de fibres de lin. L'impact de différents paramètres de formulation, de la technique de mise en œuvre et d'un vieillissement hygrothermique sur la retransformation de ces matériaux a été évalué. Les mêmes phénomènes de « régénération » sont observés, ce qui montre l'effet bénéfique de la retransformation. La fin de vie par compostage et par biodégradation est traitée. Des mesures d'énergies de combustion ont enfin permis d'estimer le potentiel de valorisation par incinération qui serait en lien avec le niveau de dégradation du PLA.

Nowadays, biocomposite materials are booming and will be a growing end-of-life issue for the future. They are based on a thermoplastic matrix (oil-based or bio-based) reinforced with vegetable fillers or fibers. Consequently, the study of their end of life through recycling, composting and incineration is a scientific and technologic challenge.The first goal of this thesis is to study the reprocessing end of life (successive injection and grinding cycles) of polypropylene (PP) based biocomposites filled with wood flour. The impact of the wood particle size and a coupling agent was assessed. Thus, a very good mechanical stability was observed up to 7 reprocessing cycles despite some degradation from the material components. Then, the reprocessing after artificial or natural UV weathering was carried out. The major trend is a “regeneration” phenomenon of mechanical properties after reprocessing in spite of strong degradations after UV weathering. Moreover, the addition of wood filler tends to restrain the PP photochemical degradation.The second goal is to study the end of life of polylactic acid (PLA) based biocomposites reinforced with flax fibers. The impact of the composition, the processing technic and humidity weathering on the reprocessing was assessed. Similar “regeneration” phenomena were observed leading to conclude to the beneficial effect of reprocessing. Then composting and biodegradation aspects were investigated. Heat release rate measurements enabled to estimate the incineration potential which could be linked to the PLA degradation rate.; Les matériaux biocomposites, en particulier les composites matrice thermoplastique biosourcée ou non renforcée de charges ou de fibres végétales, connaissent actuellement un essor significatif et présentent pour l'avenir un gisement grandissant de matières en fin de vie. En conséquence, l'étude du comportement de ces matériaux au regard de différents scénarios de fin de vie que sont le recyclage mécanique, le compostage et l'incinération constitue un enjeu scientifique et technologique important. Le premier objectif de cette thèse est d'étudier la fin de vie par retransformation (cycles successifs d'injection et de broyage) de biocomposites à matrice polypropylène (PP) chargé de farine de bois. L'impact de la taille des particules de bois et d'un agent de couplage a été évalué. Une très bonne stabilité mécanique jusqu'à 7 cycles de retransformation a été observée malgré des dégradations des différents composants du matériau. Le comportement face à la retransformation après vieillissement artificiel accéléré ou après une exposition naturelle en extérieur a été étudié. La tendance majeure dégagée est un phénomène de « régénération » des propriétés mécaniques par retransformation, et cela malgré des dégradations importantes après vieillissement. Il a été également été observé que l'ajout de bois a tendance à limiter la photodégradation du PP. Le second objectif est d'étudier la fin de vie de biocomposites à matrice acide polylactique (PLA) renforcé de fibres de lin. L'impact de différents paramètres de formulation, de la technique de mise en œuvre et d'un vieillissement hygrothermique sur la retransformation de ces matériaux a été évalué. Les mêmes phénomènes de « régénération » sont observés, ce qui montre l'effet bénéfique de la retransformation. La fin de vie par compostage et par biodégradation est traitée. Des mesures d'énergies de combustion ont enfin permis d'estimer le potentiel de valorisation par incinération qui serait en lien avec le niveau de dégradation du PLA.

International audience; This work deals with the influence of multiple injection moulding cycles on the properties of wood flour reinforced polypropylene (PP) composites. The initial wood particle size in the range of 70-150 μm and 200-500 μm was first studied. Then, the influence of the addition of a coupling agent such as polypropylene grafted with maleic anhydride (PPgma) at a given rate was investigated. Biocomposite compounds (20wt% of wood flour) are produced by twin-screw extrusion. Then, multiple injection/grinding cycles were performed (up to 7 passes) to obtain normalized samples. Mechanical (tensile, impact) and thermal (cristallinity rate) properties of the biocomposites are evaluated. The change of viscosity is assessed through rheological measurements.