Understanding the torrefaction of woody and agricultural biomasses through their extracted macromolecular components. Part 1: Experimental thermogravimetric solid mass loss

Abstract

The behavior of biomass in torrefaction is determined by that of its macromolecular components, as well as by the biomass type. However, up to now, commercial compounds were typically used for modelling biomass torrefaction. This work proposes to assess the behavior of cellulose, hemicelluloses and lignin in torrefaction through extracted fractions directly isolated from woody and agricultural biomasses (ash-wood, beech, miscanthus, pine and wheat straw) thanks to an optimized extraction procedure. The solid kinetics of these extracted fractions were analyzed through thermogravimetric analysis (TGA) in chemical regime conditions (200–300 °C at 3 °C·min−1 followed by 30 min at 300 °C). These experiments highlighted the influence of the biomass type and the sugar composition in the degradation of the polysaccharide fractions in torrefaction, particularly for hemicelluloses. Furthermore, the degree of preservation of the native structure of the macromolecular components, when extracting them from biomass, seems also having an impact their behavior, especially for cellulose. The comparison of the torrefaction solid kinetic profiles of these extracted fractions, dependent on the biomass type, to that of commercial compounds from previous studies suggest that these extracted fractions would be more suitable for biomass torrefaction modelling.