Tribology with biodiesel: A study on enhancing biodiesel stability and its fuel properties

Biodiesel is a potential renewable and biodegradable fuel source comprising of fatty acid methyl esters (FAME). It is produced from transesterification reaction of animal fats and vegetable oils. It has been selected as a suitable alternative to conventional diesel fuel as it furnishes several advantages such as reduced environmental emissions, renewability and enhanced lubricity. However, biodiesel poses various tribological challenges. It has compatibility issues with certain materials, is inherent instable and highly corrosive in nature. Sporadic efforts have been carried out to understand the aforementioned issues, however significant knowledge has not been obtained until yet, especially on stability of biodiesel of biodiesel and its lubrication behaviour. In this review, different tribological aspects of biodiesel have been highlighted by critically analysing the recent available literature. Commencing from the basics of tribology, this review extends towards the properties of biodiesel and various aspects of metal contamination, moisture absorption, temperature and storage time. Tribological issues arising due to the usage of biodiesel and the use of additives in order to stabilize biodiesel and improve its tribological compatibility have been examined. Various factors affecting the stability and usage of biodiesel (long term/short term), properties have been discussed and improvements in refining technologies for biodiesel production have been summarized. Major concerns ascribed have been reviewed and possible remedies to improve the stability of biodiesel have also been included.