Direct use of waste vegetable oil in internal combustion engines

This paper presents a comprehensive review of the work done to evaluate the effects of direct use of WVO in internal combustion engines. Many authors have shown the advantages of using straight vegetable oils or biodiesel produced from WVO as fuel, while the benefits of WVO direct use have not yet been clearly presented. The available literature still presents few papers about this topic, therefore also the use of vegetable oil, that presents physical chemical characteristics very similar to those of WVO, has been taken into account. After a brief introduction, the characteristics of WVO most affecting its use as fuel have been studied. Then several applications of WVO direct use in internal combustion engines and the available fuel supply technologies have been considered. Finally, the energetic performance and the pollutant emissions reported in literature have been deeply analyzed.