The effects of concentrates, in which glycerol plus soyabean meal replaced wheat, on physical, chemical and hygienic pellet quality characteristics were investigated. Three purities of glycerol were used, reflecting different stages of the biodiesel production process. Glycerol inclusion levels were 50, 100 and 150 g/kg concentrate dry matter (DM). Concentrates were stored under good (15°C, 60% relative humidity) or bad (20°C, 70% relative humidity) environmental conditions and for 4 or 8 weeks. Chemical quality was only slightly affected by purity and concentration of glycerol and likewise by storage conditions or duration. Ergosterol concentration indicated that glycerol of different purity had a preserving effect. The physical quality of pellets was not affected by the purity of glycerol or by glycerol concentration of up to 150 g/kg DM. Glycerol at different purity may help to stabilize the hygienic quality of pelleted compound feeds without compromising the physical quality of pellets.