Nowadays, there is an increasing awareness on the importance of biomass waste as a renewable source of energy, materials and chemicals. In this context, the European project MOBILE FLIP aims at developing and demonstrating mobile conversion processes suitable with variousunderexploited agro- and forest based biomass resources in order to produce energy carriers, materials and chemicals. One of these processes is torrefaction, which consists in a mild thermal treatment, occurring typically between 200 and 300°C during a few tens of minutes in a defaultoxygen atmosphere. The solid product obtained has thermal and processing properties closer to coal, and thus is suitable as fuel for combustion or gasification. During torrefaction, condensable coproducts are released, that may also be source of “green” chemicals. It is therefore crucial to characterize them to optimize the torrefaction process and design industrial units. Up to now, only few works have been focused on characterizing and modelling both solid and condensable species during torrefaction versus operating conditions and feedstock type. Furthermore, these studies typically include a reduced number of biomasses. Cellulose, hemicellulose and lignin,which constitute biomass macromolecular composition, are determining properties to predict biomass behaviour during torrefaction. However, torrefaction tests on these constituents are rare and always based on commercial compounds, which were proved as little representative of the native biomass. The objective of this study is to analyse the influence of biomass characteristics, mainly represented by the macromolecular composition in cellulose, hemicellulose and lignin, on the global behaviour of biomass in torrefaction, both in terms of solid mass loss and of productionprofiles of the volatile species released, in function of the operating conditions.14 biomasses from the main biomass families (deciduouswood, coniferous wood, agricultural byproductsand herbaceous crops) were selected for this study. An optimized extraction procedure was proposed to recover cellulose, hemicellulose and lignin fractions from 5 reference biomasses. Experiments were performed on a thermogravimetric analyzer coupled to a gas chromatography mass spectrometer device through a heated storage loop system (TGA-GC/MS). Solid degradation kinetics and volatile release profiles were followed during torrefaction experiments combining non-isothermal (200 to 300°C at 3°C/min) and isothermal (300°C, 30 min) conditions, ensuring the chemical regime thanks to the appropriate operating conditions. The results obtained with the raw materials demonstrated that biomass macromolecular composition is a main factor influencing biomass behavior in torrefaction. Consequently, the heterogeneity of the resource results in a diverse behavior in torrefaction, particularly in the case of agricultural biomasses. The results with the extracted components evidenced their very different behavior compared to thecommercial compounds, particularly in the case of cellulose. This suggests that a limitation could be induced by the common use in literature of commercial components for torrefaction modelling. The impact on the characterization of macromolecular components was also shown to be prevailing in their behavior in torrefaction, especially in the case of hemicellulose sugar composition and cellulose crystallinity. Furthermore, differences in release kinetics of volatile species during torrefaction were observed, even for volatiles belonging to the same chemical family (acids, furans, ketones). Derived from these results, a torrefaction model based on the additive contribution of extracted cellulose, hemicelluloses and lignin to the global behavior of biomass in torrefaction was proposed, and this for the 5 representative biomasses.

Il existe aujourd’hui une prise de conscience croissante visant à considérer les résidus de biomasse comme source potentielle d’énergie, de matériaux et de produits chimiques. Dans ce contexte, le projet européen Mobile Flip vise à développer des unités mobiles de conversion de biomasse pour la valorisation de ressources agricoles et forestières non exploitées. L’une des technologies proposées est la torréfaction, traitement thermique doux entre 200 et 300°C pendantquelques minutes et en défaut d’oxygène. Le solide torréfié présente des propriétés proches de celles du charbon et convient à la combustion ou à la gazéification. En même temps, des matières volatiles sont relâchées, dont des espèces condensables potentiellement à haute valeur ajoutée en chimie. Il est donc crucial de caractériser le solide torréfié et les espèces volatiles afin d’optimiser le procédé jusqu’à l’échelle industrielle. Jusqu’à présent, peu de travaux ont simultanément cherché à caractériser et à modéliser le comportement du solide et des espèces volatiles produites en torréfaction en fonction des conditions opératoires et du type de biomasse. De plus, ces travaux portaient sur un nombre réduit de biomasses. La composition macromoléculaire de la biomasse en cellulose, hémicelluloses et lignine impacte de manière déterminante les produits de torréfaction. Cependant, les essais de torréfaction avec ces constituants sont peu nombreux et généralement réalisés avec des composants commerciaux peu représentatifs de la biomasse brute. L’objectif de ces travaux de thèse est d’étudier l’influence des caractéristiques de la biomasse, principalement représentée par sa composition en cellulose, hémicellulose et lignine, sur le comportement global de la biomasse en torréfaction, tant en termes de perte de masse du solide que de production d’espèces volatiles, en fonction des conditions opératoires. 14 représentants des principales familles de biomasse (bois feuillus, bois résineux, sous-produits agricoles et plantes herbacées) ont été sélectionnés pour cette étude. Une procédure d’extraction optimisée a été proposée pour obtenir des fractions de cellulose, hémicellulose et lignine de 5 biomasses de référence. Les données expérimentales ont été obtenues en utilisant une thermobalance couplée à une chromatographie gazeuse et une spectrométrie de masse via un système de boucles de stockage chauffées (ATG-GC/MS). La cinétique de dégradation du solide et les profils de formation des espèces volatiles ont été étudiés au cours des expériences de torréfaction incluant une partie non-isotherme (200 à 300°C, 3°C/min) suivie d’une partie isotherme (300°C, 30 min), dans des conditions expérimentales assurant le régime chimique. Les résultats obtenus avec les biomasses brutes montrent que la composition macromoléculaire de la biomasse est un facteur clé influant sur son comportement en torréfaction. Par conséquent, l’hétérogénéité de la ressource se traduit par une diversité de comportements en torréfaction, en particulier pour les biomasses agricoles. Il a été observé un comportement très différent pour les composants extraits comparés aux composants commerciaux, particulièrement dans le cas de la cellulose. Ceci montre que l’usage commun de composants commerciaux pour bâtir les modèles de torréfaction n’est pas pertinent. L'impact des caractéristiques des composants macromoléculaires sur le comportement en torréfaction a été aussi mis en évidence, particulièrement en ce qui concerne la composition en sucres des hémicelluloses et la cristallinité de la cellulose. En outre, des différences de profils de production des espèces volatiles ont été observées, même pour des composés de même nature chimique. A partir de ces résultats, un modèle de torréfaction basé sur la contribution additive de la cellulose, des hémicelluloses et de la lignine extraites est proposé pour décrire le comportement global de la biomasse en torréfaction, et ceci pour les 5 biomasses de référence. / Nowadays, there is an increasing awareness on the importance of biomass waste as a renewable source of energy, materials and chemicals. In this context, the European project MOBILE FLIP aims at developing and demonstrating mobile conversion processes suitable with variousunderexploited agro- and forest based biomass resources in order to produce energy carriers, materials and chemicals. One of these processes is torrefaction, which consists in a mild thermal treatment, occurring typically between 200 and 300°C during a few tens of minutes in a defaultoxygen atmosphere. The solid product obtained has thermal and processing properties closer to coal, and thus is suitable as fuel for combustion or gasification. During torrefaction, condensable coproducts are released, that may also be source of “green” chemicals. It is therefore crucial to characterize them to optimize the torrefaction process and design industrial units. Up to now, only few works have been focused on characterizing and modelling both solid and condensable species during torrefaction versus operating conditions and feedstock type. Furthermore, these studies typically include a reduced number of biomasses. Cellulose, hemicellulose and lignin,which constitute biomass macromolecular composition, are determining properties to predict biomass behaviour during torrefaction. However, torrefaction tests on these constituents are rare and always based on commercial compounds, which were proved as little representative of the native biomass. The objective of this study is to analyse the influence of biomass characteristics, mainly represented by the macromolecular composition in cellulose, hemicellulose and lignin, on the global behaviour of biomass in torrefaction, both in terms of solid mass loss and of productionprofiles of the volatile species released, in function of the operating conditions.14 biomasses from the main biomass families (deciduouswood, coniferous wood, agricultural byproductsand herbaceous crops) were selected for this study. An optimized extraction procedure was proposed to recover cellulose, hemicellulose and lignin fractions from 5 reference biomasses. Experiments were performed on a thermogravimetric analyzer coupled to a gas chromatography mass spectrometer device through a heated storage loop system (TGA-GC/MS). Solid degradation kinetics and volatile release profiles were followed during torrefaction experiments combining non-isothermal (200 to 300°C at 3°C/min) and isothermal (300°C, 30 min) conditions, ensuring the chemical regime thanks to the appropriate operating conditions. The results obtained with the raw materials demonstrated that biomass macromolecular composition is a main factor influencing biomass behavior in torrefaction. Consequently, the heterogeneity of the resource results in a diverse behavior in torrefaction, particularly in the case of agricultural biomasses. The results with the extracted components evidenced their very different behavior compared to thecommercial compounds, particularly in the case of cellulose. This suggests that a limitation could be induced by the common use in literature of commercial components for torrefaction modelling. The impact on the characterization of macromolecular components was also shown to be prevailing in their behavior in torrefaction, especially in the case of hemicellulose sugar composition and cellulose crystallinity. Furthermore, differences in release kinetics of volatile species during torrefaction were observed, even for volatiles belonging to the same chemical family (acids, furans, ketones). Derived from these results, a torrefaction model based on the additive contribution of extracted cellulose, hemicelluloses and lignin to the global behavior of biomass in torrefaction was proposed, and this for the 5 representative biomasses.