Reforming of pure glycerol, crude glycerin, and methanol (pure and in the presence of Na(2)CO(3)) in supercritical water was investigated. Continuous experiments were carried out at temperatures between 450 and 650 degrees C, residence times between 6 and 173 s, and feed concentrations of 3-20 wt%. For methanol the gas products are mainly H(2), CO(2), and CO. The carbon-to-gas efficiency and the observed activation energy for pure methanol are higher than for methanol with Na(2)CO(3). This can be explained by assuming different decomposition mechanisms for pure methanol and methanol with Na(2)CO(3). For glycerol, H(2), CO, CO(2), CH(4), and higher hydrocarbons are produced. The carbon-to-gas efficiencies of crude glycerin and pure glycerol are comparable. Overall, 2 of the 3 carbon atoms present in glycerol end up in carbon oxides, while 1 carbon atom becomes C(x)H(y). The overall mechanism of glycerol decomposition involves the dehydration of 1 mole of H(2)O/mole glycerol. For both, methanol and glycerol at carbon-to-gas efficiencies below 70%, the gas yields (mole/mole feed) and carbon-to-gas efficiency correlate well. (C) 2011 Elsevier B.V. All rights reserved.