This paper presents the first results of an investigation carried out by the authors on the potentialities of biodiesel as an alternative fuel based on strategic considerations and field experiences in boilers and diesel engines. The operation of a biodiesel fuelled boiler has been checked for some months. The engines have been bench-tested and then installed on urban buses for normal operation. Distances, fuel consumption and emissions (CO2, CO, HC and NOX) have been monitored; in addition devices wear and tear, oil and air filters dirtiness and lubricant degradation have been checked. Further investigations have also been devoted to assess some environmental aspects of bio-diesel. In particular the benefit of biodiesel to the total net emission of CO2 during the whole life cycle has been studied and the net energy requirement has been evaluated. Finally, the global environmental support to the production of biodiesel has been studied according to the emergy analysis.