Influence of lignin content on biomass particle morphology and its implications for bioenergy conversion efficiency in woody and herbaceous species

This study reveals the coupled effects of lignin content and monomeric composition on the aspect ratio (AR) of biomass particles and associated heat and mass transfer characteristics. Sixteen woody and herbaceous biomasses were analyzed for chemical composition and AR after milling. Opposite trends were observed between biomass types: in herbaceous materials, increasing lignin content was associated with lower AR, whereas in woody materials higher lignin content corresponded to higher AR. Fourier-transform infrared analysis further indicated that, for woody biomass, the syringyl to guaiacyl (S/G) ratio is closely related to particle morphology, with higher guaiacyl fractions favoring higher AR particles. A sphericity-based model was used to evaluate the influence of AR on external and internal heat and mass transfer characteristics. The analysis shows that increasing AR enhances idealized external transfer potential while increasing internal transport resistance. Thermogravimetric analysis of representative biomasses confirms that the influence of AR on apparent pyrolysis behavior is non-linear, reflecting the competing roles of external and internal transport processes. These results link lignin chemistry, particle morphology, and transport behavior, providing guidance for biomass pretreatment and bioenergy conversion.