Batch reactors made of stainless steel and Inconel (R) 625 were used for the hydrothermal gasification of glucose and beech sawdust under both subcritical (350 degrees C) and supercritical (400 degrees C) conditions at a pressure of 30 MPa. These tests were executed over residence times ranging from 60 to 300 mm. The amounts of solid, liquid and gas produced and the composition of the resulting gas phase were measured. The results showed that a higher H-2 output was achieved in the stainless steel reactors, while the Inconel 625 reactors were more effective for the synthesis of CH4 and light hydrocarbons. A visual observation of the metal surfaces was performed using scanning electron microscopy to explain the persistence of catalytic activity even after an aging treatment and many hours of operation. (C) 2013 Elsevier B.V. All rights reserved.