Valorization of sawdust biomass for biopolymer extraction via green method: Comparison with conventional process

The valorization of sawdust (SW) biomass by-product, to extract cellulose through alkali and bleaching processes, including side-streams to recover hemicellulose and lignin, is performed with the intention of evaluating differences with a proposed green method (GM). The study is developed with the intention of having a process at laboratory scale without leading to the complicated nanoscale processing. This study contemplates a process with scalable characteristics for the future, which contributes to wood processing waste around the world. Particularly, agroindustrial wastes from Durango (SW_T1) and Hidalgo (SW_T2), local communities of Mexico, were studied. SW_T1 and SW_T2 samples were processed with ethanol, sodium hydroxide followed by bleaching with sodium chlorite/acetic acid to remove, extractives (E), hemicellulose (H) and lignin (L), respectively. Selected-SW_T2 was processed through a proposed GM using hydrogen peroxide/sodium hydroxide. On the basis of results including Fourier transform infrared spectroscopy, thermogravimetric/differential analysis (TGA/DTG), X-ray diffraction (XRD), dynamic light scattering, high heating value, scanning electron microscopy techniques and chemical composition, GM was capable of producing a biomass rich in α-cellulose (58.0%: SW_T2-C), whereas processed SW_T1 and SW_T2 through conventional method led to a more percentage of H, β- and γ-C mixtures than α-polymorphous; 41.0% and 51.0%, respectively. This new method could impact of an important manner to the development of biodegradable thermoplastics. The approximation, from deconvolution of TGA/DTA, led to determine adequately the composition of hemicellulose (SW_T1-C: 51.0%, SW_T2-C: 36.0–0.00%), lignin (SW_T1-C: 17.0%, SW_T2-C: 20.0%) and cellulose (SW_T1-C: 32.0%, SW_T2-C: 44.0%). XRD analysis also indicated that samples contain the following percentage of polymorphous cellulose compounds: SW_T1-C (Type II: 71.3%), SW_T2-C (Type I α: 44.6% and II: 41.4%) and SW_T2-C-GM (Type II: 38.8%), which confirms that the combination of the type of biomass and the applied pretreatment plays a fundamental role for final applications; in this case, it can be appropriate for elastomers and thermoplastic uses. As a final point, the cellulose composition and thermal stability of both sources is comparable with the commonly used raw material for commercial products.