Olive pomace oil derives from the oil left in the olive fruit pulp than remains after pressing extra virgin olive oil. To extract olive pomace oil, the pulp is treated with solvents. The resultant oil contains impurities and may undergo several heating and filtering processes to refine it to an acceptable standard. To make it satisfactory to consumers, it must be blended with virgin olive oil before use. Therefore, another uses for this oil could be soap production or its recycling to produce biodiesel. Exhaust emissions, noise and sound quality of a direct injection diesel engine fueled with olive pomace oil methyl ester (OPME) blends were studied at several steady-state engine operating conditions. Results showed that the higher the content of OPME in the blends, the lower the CO emissions, whereas NOx increased, keeping fuel consumption constant. Moreover, it was found that cetane number exhibited a stronger effect over noise production than bulk modulus, whereas the reverse effect was found concerning NOx emissions. Biodiesel blends reduced air and noise pollution, while improving sound quality. Therefore, the higher the percentage of biodiesel in blends, the lower the pollution emitted by the engine. (C) 2011 Elsevier Ltd. All rights reserved.