A concise review of glycerol derivatives for use as fuel additives.

Due to renewable fuel mandates worldwide, the increase in biodiesel production has caused an oversupply of low-cost glycerol on the markets, which can negatively affect the sustainability of the biodiesel industry as a whole. In order to avoid that scenario, the transformation of glycerol into value-added products has been investigated, and the production of additives for internal combustion engine fuels is one good example of glycerol valorization. The present work presents a summary of the literature describing the most important chemical pathways through which glycerol can be converted into fuel additives, to be subsequently mixed with either gasoline, biodiesel, or diesel fuel. The focus is on the three major categories, namely glycerol acetals/ketals, ethers, and esters (acetates). Moreover, the effectiveness of the different glycerol-derived compounds is illustrated through several examples from the literature. Finally, a few research gaps on the topic are identified and suggestions for future work are described.