Experimental Investigation of Glycerol Derivatives as Low-Concentration Additives for Diesel Fuel

The worldwide adoption of renewable energy mandates, together with the widespread utilization of biofuels has created a sharp increase in the production of biodiesel (fatty acid alkyl esters). As a consequence, the production of glycerol, the main by-product of the transesterification of fatty acids, has increased accordingly, which has led to an oversupply of that compound on the markets. Therefore, in order to increase the sustainability of the biodiesel industry, alternative uses for glycerol need to be explored and the production of fuel additives is a good example of the so-called glycerol valorization. The goal of this study is therefore to evaluate the suitability of a number of glycerol-derived compounds as diesel fuel additives. Moreover, this work concerns the assessment of low-concentration blends of those glycerol derivatives with diesel fuel, which are more likely to conform to the existing fuel standards and be used in unmodified engines. The various blends described in this article were tested on a heavy-duty diesel engine converted to single-cylinder operation. The overall behavior and the impact of the fuel blends on the engine's combustion, performance, and emissions were investigated. The results showed that the additives caused a modest decrease in engine-out soot concentrations along with slightly reduced hydrocarbon and carbon monoxide emissions. In addition, the blends appeared to have a positive impact on the soot-NOx trade-off. Finally, as expected, volumetric fuel consumption was slightly increased with the oxygenated blends, due to their lower heating values. In conclusion, even though the use of the glycerol derivatives in low concentrations did not produce dramatic outcomes, the results showed that they can nevertheless be used as a means to decrease fossil fuel usage in the transportation sector.