investigation into the lignin decomposition mechanism by analysis of the pyrolysis product of pinus radiata lignin pyrolysis chemistry was investigated via the analysis of the products obtained from the fast pyrolysis of a pine wood at different temperatures methoxy phenols such as guaiacols and eugenols were produced mainly at 375 and 475c while nonmethoxy phenols such as alkyl phenols and pyrocatechols were dominant at 525 and 575c at 575c aromatic hydrocarbons were formed together with larger amounts of light hydrocarbon gases when the temperature was increased from 375 and 475c the yield of pyrolytic lignin was increased whereas its average molecular weight was decreased at 525c smaller molecular pyrolytic lignin with a maximum concentration of phenolic hydroxyl groups was produced due to the increased secondary cracking of the reaction intermediates on the other hand at 575c larger molecular pyrolytic lignin with smaller amounts of phenolic hydroxyl groups was produced due to the increased condensation activity of the pyrolysis reaction intermediates