produce biopolymers and biofuels with lower carbon footprints than their conventional counterparts [5; 6]. Lignocellulosic biomass, derived from forests, is the most abundant type of biomass and a valuable source of natural polymers, such as cellulose, hemicellulose, and lignin. In turn, lignin is the second most abundant natural polymer and can be recovered as a byproduct of the pulp and paper industry [8]. Lignin is an amorphous and heterogeneous polymer with high molecular weight and takes the form of a complex three-dimensional structure of alkylphenolic rings that result from the polymerization of three types of aromatic monomers: p-coumaryl alcohol, coniferyl alcohol, and sinapyl alcohol [9; 10]. These copolymerize to form the lignin structural units syringl (S), guiaacyl (G), and p-hydroxyphenyl (H), with their proportions in the polymer depending on the biomass source (i.e., the type of vegetation) [11]. Due to its partly aromatic backbone, lignin offers good thermal stability and fire retardancy, making it suitable for applications where increased heat resistance and improved fire reaction performance is required [12]. Moreover, lignin is very stiff, owing to the strong bonds that hold the monomers together. The incorporation of lignin in resins used in the production of FRP composites; therefore, it has excellent potential to enhance the sustainability of these materials by increasing their renewable content as well as by potentially improving their mechanical properties at ambient temperature and their high temperature resistance (due to the presence of aromatic rings with high thermal stability) and fire reaction properties. Through the biorefining of lignin, valuable aromatic structures akin to phenol can be obtained; however, the depolymerization processes required to achieve this are costly [9; 13], which explains why this natural polymer has been mostly incorporated into resins, adhesives, foams, and other polymeric materials in its macromolecular form [14; 15; 16; 17; 18; 19]. In fact, several efforts have been made in recent years to incorporate lignin into the polymer structures of phenolic [20; 21; 22], polyurethane [23], fumaric [24], epoxy [25; 26; 27], polyester [28; 29; 30], vinyl ester [30; 31], and acrylate-based [32; 33] resins. A common issue in these studies is determining the actual role of the macromolecular lignin in the resulting material. The combination of base polymer and lignin can result in (i) a composite in which the lignin acts as a filler and there is a well-defined interface with the base polymer, (ii) a blend of lignin and a base polymer wherein interdiffusion between the two polymers occurs, and (iii) a copolymerized network in which lignin acts as a reactive component, either integrating the main polymer structure or functioning as a crosslinking agent [11; 27]. The actual incorporation mechanism will be dependent on several factors, including but not limited to the compatibility between the base polymer and the type of lignin used, as well as the process(es) used for lignin incorporation. Depending on the type of combination between lignin and the base polymer, the properties of the resulting material can vary significantly, with both reductions and increases in performance having been reported in previous studies [11]. Among the previously mentioned resin types, those derived from phenol are very interesting for applications where the thermal behavior is a relevant performance requirement, given their low flammability and good mechanical properties at relatively high temperatures (up to around 200 \({}^{\circ}\)C [34; 35]). Such properties are highly desirable in FRP composites used in many applications. However, the use of phenolic resins in FRP materials is hindered by difficulties associated with the production, reinforcement, and thermal curing of these resins, in addition to their brittleness at ambient temperature and low impact resistance [36; 37].