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L'agroforesterie consiste à faire pousser des arbres en association avec des cultures agricoles et / ou en présence de troupeaux d'animaux. Les avantages d'une telle pratique sont nombreux, tant du point de vue de la production agricole que de la protection de l'environnement. Sur le terrain, on observe une meilleure productivité individuelle des arbres agroforestiers mesurée (jusqu'à trois fois le volume raméal des mêmes arbres mais en conditions forestières). La récolte de ces branches est une nécessité pour la bonne gestion agricole. La valorisation de cette biomasse permettrait d'améliorer la rentabilité des parcelles agroforestières et d'inciter les agriculteurs à intégrer davantage les arbres dans leur environnement de production. Et pour les industriels, ce serait également la possibilité d'obtenir plus facilement et durablement des matières premières de qualité dans des démarches agroécologiques reconnues. Le projet Agrobranche visait à étudier la valorisation de cette biomasse dans les domaines des matériaux et de la chimie biosourcés. Agrobranche a permis de quantifier la productivité de ces systèmes et de définir les contours de leur rentabilité. Les partenaires aval ont pu qualifier le potentiel industriel dans les domaines des matériaux composites et panneaux, tout en explorant les principales caractéristiques chimiques des plaquettes agroforestières selon 4 essences principales (noyer, peuplier, châtaignier et chêne), mais aussi à partir de bois déchiqueté issus de plateformes de bois énergie (mix d'essences). Le comportement des matériaux testés est très encourageant, avec des performances souvent égales aux standards issus de matériaux comme l'épicéa forestier ou le miscanthus. Mais l'intérêt, qui a pu être approché dans l'ACV, réside également dans le mode de production. Car produire de la plaquette agroforestière concilie production biomasse et maintien de la production agricole contrairement aux productions biomasses dédiées. Et les services rendus pèsent dans la balance auprès des acteurs de la filière, qu'ils soient les clients finaux comme les intermédiaires. more...

International audience; Current environmental concerns push towards more sustainable and local practices for biomass production. In this regard, agroforestry has been highlighted by researchers and policies as a highly efficient approach for carbon sequestration (between 1.5 and 4 t C/ha/year), and a sustainable alternative to deforestation with many agricultural benefits: deeper rooting of trees in soil, enhanced biomass productivity, crop fertilization... Agroforestry implies regular branch cuts that are processed into wood chips and mostly used as energy wood or soil mulching. New higher added-value chains could be considered such as reinforcements or specific molecules for bio-based materials and chemistry. Besides, since 90’s, Wood-Plastic Composites (WPCs) have experienced significant growth, particularly in building (decking & siding), and constitute the largest share of bio-based composites developed at an industrial scale. Nevertheless, the quality of WPCs and variability in their performance are major technological issues for their implementation in industrial applications. This could be related to the difficulty in tracing the various origin of wood fillers as well as the different processing steps, from wood drying and defibration process to composite manufacturing, that are not well controlled. Indeed, numerous interdependent parameters govern the final properties of WPCs, such as biochemical composition, presence of metallic and chemical contaminants (binders, wood treatment residues, varnishes, etc.), (micro)structure, thermal stability, mechanical properties of wood fillers, and the control of their milling/granulometry and further processing into composite materials. In this context, the development of quality-controlled agroforestry wood fillers in terms of granulometry (size and shape factor), chemical composition and physical (microstructure, mechanical) properties is therefore strategic for their implementation in wood-based products. This work investigates and evidences the influence of wood species (poplar, oak, walnut, chestnut)) and filler size and shape on the microstructure and mechanical properties of polypropylene (PP) / wood composites manufactured by extrusion/injection moulded. Moreover, wood from three recovery platforms in Brittany (mix of several species) was also investigated to evaluate the potential of existing agroforestry feedstocks. more...

International audience; In many industrial fields, the development of porous and light polymer composite structure is of great interest. These structures may have several advantages compared to a massive solid of the same chemical nature, such as better mechanical properties, cushioning, insulation, sound and heat absorption. As an example, foams are used in the sport, pharmaceutical, aeronautic and packaging industries. For these applications, petroleum based thermoplastics are widely used as polymer matrix, but, due to the shortage of fossil resources and the rise of environmental concerns, biopolymers (bio-based, bio-degradable and/or bio-compatible polymer) are more and more used.There are two main routes to produce biopolymer foams depending on the blowing agent used, which can be either chemical (CBA) or physical (PBA). CBA are able to release a gas upon thermal decomposition, but they have some drawbacks, among which the necessity of high process temperatures, the solid residues on the foam and their toxicity. PBA appear as an alternative to these chemical agents, supercritical CO2 and N2 being the most used.Batch foaming of polymers is a process which can be carried out in an autoclave. The samples are saturated in a pressure vessel a certain time, and their foaming is achieved by inducing an instability into the system. Pressurised gas solubility in polymers increases with pressure but decreases with temperature. Therefore, in the batch foaming process, the instability can be induced by a sudden drop in pressure (pressure quenching) or by a raise in temperature thus causing polymer foaming.This foaming technology has been largely used for different polymers such as polystyrene [2], polycaprolactone [3], polyethylene/polypropylene [4] and, polyethylene terephthalate [5]; among others. This work is focused on the foaming of PLA-based biocomposites using (ligno-)cellulosic fibres by supercritical CO2 assisted batch process by pressure quenching, the study of the operating conditions, the influence of the nature of the fibres and their characteristics on the porosity and morphology of the obtained foams. more...