SEPTEMBER 2012 | VOL. 11 NO. 9 | TAPPI JOURNAL 41 T he purpose of a biorefinery is to convert wood, agri- cultural products, byproducts, and agricultural wastes or other biomass into products with added value. This goal is often achieved using different physical, physicochemi- cal, or chemical pretreatment processes. Lignocellulosic biomass and agricultural wastes are appealing as biorefin- ery feedstock because of their abundance, low cost, and global availability [1,2]. The forest biorefinery combines processes aimed at the recovery and separation of the main components of wood: cellulose, hemicellulose, and lignin. The continuous biomass fractionation process yields a liquid stream rich in hemicellulosic sugars, a solid cellulose stream, and a lignin-rich liquid stream—all of which can be used to produce ethanol fuel, chemicals, and lignin, respectively, for resin production [1,3–5]. Lignin is a biorefinery byproduct produced following the delignification process, which is necessary to refine cellulose and hemicellulose before enzymatic or acid hydrolysis [6,7] that occurs in the production of bioethanol and/or other ma- terials [8]. Due to its high abundance and low cost, lignin has long attracted attention as an alternative to petroleum-derived products [9,10]. Lignin has many functional groups, including aromatic rings, phenolic hydroxyls, carboxyl, and aliphatic hydroxyl groups. Because it is rich in phenolic aromatic rings, lignin has many advantages as a replacement for phenol in the preparation of resol-type phenolic resins, epoxy resins, and other resins [11–15]. The use of lignin as a raw material to produce environmen- tally friendly products reduces the demand of nonrenewable resources and provides a safe alternative to phenol, a toxic petrochemical [16]. Lignin has other applications, as well. For example, carboxymethyl lignin can be used as a stabilizing agent in aqueous ceramic suspensions; specifically, carboxy- methylated lignin derived from sugarcane bagasse has been successfully used as a stabilizing agent for alumina suspen- sions [17]. Formulations based on lignins have filmogenic properties that, when combined with the hydrophobicity of this macromolecule, have pointed to applications such as slow-release coatings for fertilizers [18]. However, most of the lignin that is produced is burned [19] rather than used to pro- duce value-added materials. Nevertheless, this scenario is changing, due to the increasing presence of biorefineries, in- cluding lignocellulosic feedstock biorefineries [4, 20], that aim to use lignin to produce polymers and other materials. Composites from a forest biorefinery byproduct and agrofibers: Lignosulfonate-phenolic type matrices reinforced with sisal fibers CRISTINA GOMES DA SILVA, FERNANDO OLIVEIRA, ELAINE CRISTINA RAMIRES, ALAIN CASTELLAN, AND ELISABETE FROLLINI BIOREFINERY PEER-REVIEWED ABSTRACT: The replacement of phenol with sodium lignosulfonate and formaldehyde with glutaraldehyde in the preparation of resins resulted in a new resol-type phenolic resin, sodium lignosulfonate-glutaraldehyde resin, in addition to sodium lignosulfonate-formaldehyde and phenol-formaldehyde resins. These resins were then used to prepare thermosets and composites reinforced with sisal fibers. Different techniques were used to characterize raw materials and/or thermosets and composites, including inverse gas chromatography, thermogravimetric analysis, and mechanical impact and flexural tests. The substitution of phenol by sodium lignosulfonate in the formulation of the composite matrices increased the impact strength of the respective composites from approximately 400 Jm -1 to 800 J m -1 and 1000 J m -1 , showing a considerable enhancement from the replacement of phenol with sodium lignosulfonate. The wettability of the sisal fibers increased when the resins were prepared from sodium lignosulfonate, generating composites in which the adhesion at the fiber-matrix interface was stronger and favored the transference of load from the matrix to the fiber during impact. Results suggested that the composites experienced a different mechanism of load transfer from the matrix to the fiber when a bending load was applied, compared to that experienced during impact. The thermogravimetric analysis results demonstrated that the thermal stability of the composites was not affected by the use of sodium lignosulfonate as a phenolic-type reagent during the preparation of the matrices. Application: Application of sodium lignosulfonate in the preparation of resins used in the manufacture of com- posites reinforced with sisal fibers adds value to byproducts generated in forest biorefineries.