In the liquefaction process, the micellar-like broken down fragments produced by hydrolysis are degraded to smaller compounds by dehydration, dehydrogenation, deoxygenation and decarboxylation. These compounds once produced, rearrange through condensation, cyclization and polymerization, leading to new compounds. Thermal depolymerization and decomposition of biomass, cellulose, hemicelluloses and products were formed as well as a solid residue of charcoal. The mechanism of pyrolytic degradation of structural components of the biomass samples was separately studied. Cleavage of the aromatic C-O bond in lignin led to the formation of one oxygen atom products, and the cleavage of the methyl C-O bond to form two oxygen atom products is the first reaction to occur in the thermolysis of 4-alkylguaiiacol at 600-650 K. Cleavage of the side chain C-C bond occurs between the aromatic ring and the cc-carbon atom. (C) 1999 Elsevier Science Ltd. All rights reserved.