Lignin has gained momentum as a renewable material because it is the largest natural source that can provide aromatic compounds in a wide range of applications. However, its heterogeneity in terms of high polydispersity molar mass distribution and variety of functional groups has limited the direct production of added-value lignin-derivatives. Among the alternatives to obtain more homogeneous lignin cuts is solvent fractionation. However, it is not well understood how different solvents influence lignin partition, and thus it is difficult to establish a rational solvent order to perform it. Thus, the purpose of this work was to understand Eucalyptus urograndis kraft lignin partition in organic solvents through the application of three solubility parameter theories: Hildebrand, Hansen (HSP), and Functional (FSP). Through the theories studied, FSP provided the best representation of lignin partition in organic solvents. In addition, the influence of solvents’ solubility parameters on lignin solubility was investigated by multiregression analyses, which revealed that only the polar solvent parameter showed statistical relevance to describe lignin solubility. The results of this work may contribute to the effective development of technical lignins’ fractionation, allowing the production of higher-value lignin derivatives, increasing the profitability of biorefineries, and establishing a sustainable bio-based economy.

The aim of becoming a society based on the rational utilization of the natural resources, has led to the consideration of many alternatives by academic and industrial sectors. The forest sector may be particularly prominent in trying to achieve these goals when using residues of their processes, for timber and pulp production. One of the most important requirements in society is the energy production. Co-products of wood processing and cellulose mills can be used for bioenergy generation. The densification of biomass involves handling, transportation and storage issues, and furthermore, when industrial forest residues such as lignin are added to this biomass, the final energetic product may have some improved properties, adding value to the chain. The purpose of this study was to evaluate the usage of the woody industrial waste, the sawdust from Joannesia princeps Vellozo enriched with Kraft lignin as an additive, aiming to produce briquettes. One of the main findings from this work was the possibility to obtain a briquette with better properties (higher bulk density and higher resistance) when using 6% of Kraft lignin as an additive and a pressure of 1500 PSI.