Abstract
The transition toward a sustainable bioeconomy relies on efficient biomass valorisation processes, which critically depends on the ability to predict and control the flow behaviour of solid biomaterials like lignocellulosic biomass (LCB). However, the rheological properties of LCB remain difficult to characterise due to its intrinsic complexity, including broad particle size distributions, irregular and non-spherical morphologies, presence of moisture and additional variability arising from biological and seasonal factors. Building on these challenges, this study investigates how particle-scale properties influence LCB macroscopic flow under quasi-static and dense regimes, using wood sawdust as a model material. Beech and fir sawdust were characterised then tested under above mentioned flow regimes using a shear cell, a powder rheometer and a rotating drum. Under quasi-static conditions, flow function coefficient (FFC) values ranged from 5.2 to 9.8 for both materials, indicating easy-flowing behaviour. In dense regimes, FT4 tests showed that beech required higher mechanical energy than fir to achieve steady flow, while rotating drum experiments revealed cohesion indices of 0.15–0.22 for beech and 0.20–0.28 for fir. Additionally, experimental videos were analysed using Particle Image Velocimetry (PIV) to assess internal flow dynamics. These results demonstrate that flow behaviour is strongly influenced by particle size and shape, with fibrous and irregular morphologies promoting interlocking and entanglement.
