Lignin as a naturally occurring polyphenolic compound has an excellent potential to replace petroleum-based phenol in formulation of phenol-formaldehyde adhesive that are used in manufacturing of engineered wood products. However, there are three major obstacles in application of polymeric lignin as phenol replacement: 1) low reactivity toward phenol, 2) high molecular weight, and 3) high polydispersity or heterogeneity. Depending on the source (hardwood, softwood or annual crops), and isolation processes (kraft, sulphite, organosolv, steam explosion enzymatic pretreatment) lignin properties will differ. Choosing suitable lignin with potential higher reactivity toward phenol in this study helped us to formulate a 100% lignin-based phenolic adhesive that had shown excellent water resistance and mechanical properties. The lap shear strength results of analysed plywood samples (using 100% lignin-based adhesive) were similar to a commercially phenol resorcinol formaldehyde (PRF) adhesive formulated for manufacturing of plywood and ordinated strand board (OSB).

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