This invention is directed to a method of preparing a natural resin by liquefying wood, bark, forest residues, wood industry residues, or other biomass using fast pyrolysis in order to produce product vapours and char. Following removal of the char from the product vapours, a first set of compounds are removed from the product vapours by rapid quenching in order to obtain a remaining selected product vapour from which a natural resin is obtained. The natural resin comprises a total phenolic content from about 30 % to about 80 % (w/w), and is further characterized as having a pleasant smoky odour. The natural resin has surprisingly been found to be suitable for use within adhesive formulations without requiring any further extraction or fractionation procedures. Adhesives comprising up to 60 % natural resin have been prepared and tested in board production and found to exhibit similar properties associated with commercially available resins. The natural resin may substitute for phenol, or for both phenol and formaldehyde within phenol-containing resins. Similarly, the natural resin can replace a substantial part of the components within urea-containing resins.