Quality of Microfibrillated Cellulose Produced from Unbleached Pine Sawdust Pulp as an Environmentally Friendly Source

The implementation of biorefineries of sawmill residues is an opportunity in countries or regions with a high rate of afforestation. Microfibrillated cellulose (MFC) is a high-value product that can be obtained from the cellulosic fraction. However, many critical aspects involved in its production and characterization are not clarified yet. This study analyzes the physical and morphological properties of laboratory-obtained MFC from different sources, among them, hardwood and softwood industrial pulps and unbleached pine sawdust pulps from conventional and non-conventional processes, aiming to evaluate and predict the relationship between the characteristics of the pulps and those of MFC. MFC dimensions and the properties of the MFC suspensions (viscosity, transmittance, others) were determined. The results showed that unbleached pine sawdust pulp is a low-cost and environmentally friendly raw material for MFC production and that this MFC can be produced with less energy and on a small scale than MFC from industrial pulps. A principal component analysis was assessed, showing that pine pulps from sawdust produce MFC of similar characteristics to conventional pine pulps from chips (high relative transmittance, short microfibrils, and small widths visible with the optical microscope), so fiber length of the original pulp is not so relevant than high fiber width and fiber coarseness.