In this study, a comparison of the hydrothermal behavior of various biomasses such as phyto mass, zoo mass, phyto mass/K2CO3 and glucose K2CO3 (model system for the phyto mass) is given. The experiments have been carried out in a batch reactor at 500 degrees C, 30 MPa with a reaction time of 1 h. The phenol content of the aqueous phase obtained by biomass conversion was remarkably high. Actually, phenols and furfurals are the most important intermediates formed during the hydrothermal conversion of biomass. No furfural and its derivatives were observed in this study. In order to investigate the hydrothermal biomass conversion in detail, the behavior of the phenols and furfurals, under the same experimental conditions was also studied. The differences between the feedstocks have been discussed. Likely variations of the products and intermediates formed are a consequence of differences in the composition of the feedstock, namely, salts and proteins which seem to influence the chemistry of hydrothermal conversions. (C) 2012 Elsevier B.V. All rights reserved.