This work analyses the influence of three biodiesel-derived impurities (CH3OH, CH3COOH and KOH) on the aqueous phase reforming of glycerol at 220 degrees C and 44 bar using a Ni-La/Al2O3 catalyst. The experiments were planed according to a factorial 2(k) design and analysed by means of an analysis of variance (ANOVA) test to identify the effect of each impurity and all possible binary and ternary combinations. The presence of CH3OH decreased the glycerol conversion, while CH3COOH and KOH decreased and increased the gas production, respectively. Catalyst deactivation took place under acidic conditions due to the loss of part of the active phase of the catalyst through leaching. The gas phase was made up of H-2, CO2, CO and CH4. KOH exerted the greatest influence on the gas composition, increasing H-2 production due to the greater gas production and the lower H-2 consumption in the hydrogenation reactions. The liquid phase was made up of aldehydes, monohydric and polyhydric alcohols, C3 and C4 ketones and esters. CH3OH increased the proportion of monohydric alcohols, while CH3COOH promoted dehydration reactions, leading to an increase in the relative amount of C3-ketones. (C) 2016 Elsevier B.V. All rights reserved.