The transesterification of triglycerides extracted from oilseeds to obtain biodiesel fuel yields up to 14% by weight of glycerol as by-product. The liquid-phase oxidation of glycerol with air on platinum catalysts was investigated to prepare valuable oxidation products such as glyceric acid or dihydroxyacetone. The effect of the pH (pH range 2-11) and of different metal catalysts was studied. The selectivity to glyceric acid can be as high as 70% at 100% conversion on Pd/C at pH 11. On Pt/C catalyst, glyceric acid was still the main product (55% selectivity); but the deposition of bismuth on platinum particles orientates the selectivity towards the oxidation of the secondary hydroxyl group to yield dihydroxyacetone with a selectivity of 50% at 70% conversion.