Biodiesel by-product has potential as clean burning fuel additive

Glycerol waste from the biodiesel production process could be ‘simply’ converted into a clean burning sustainable fuel, according to new research from scientists at the University of Miskolc, Hungary, and King Abdullah University of Science and Technology (KAUST) in Saudi Arabia.

Specifically, the researchers have investigated using glycerol carbonate, generated from the excess glycerol of biodiesel production from waste vegetable oils and animal fats, as a fuel additive.

“The increasing demand for biodiesel has led to a substantial increase of glycerol supply in the global market and a dramatic fall in the price of glycerol which has warranted alternative uses of glycerol,” the authors write in the abstract to the study, published in the journal Sustainable Energy and Fuels.

“One potential way to deal with the crude glycerol overflow is to convert it to glycerol carbonate (GC) and use GC as a fuel or fuel additive.”

Key to the research is the idea that hydrocarbon derived from crude oil can be replaced with compounds that also contain oxygen. According to a KAUST statement, as well as reducing particulate emissions, burning these oxygenated compounds generates less carbon dioxide.

"Our results show that glycerol carbonate has great potential to promote cleaner combustion as a fuel additive," said KAUST’s Binod Giri, one of the lead authors.

Oxygenated compounds burn with near-zero soot emissions if the oxygen content is over 33% of the total mass, and glycerol carbonate has an oxygen content of 59%. Using computational analysis, Giri and colleagues explored the effect of various pressures and temperatures on the combustion reactions. From this they identified conditions in which glycerol carbonate burnt cleanly, while also generating the compound 3-hydroxypropanal, known to greatly reduce the production of soot.

“This work has the potential to change the future directions of fuel engine research,” said Aamir Farooq, who supervised the research. 

Titled Glycerol carbonate as a fuel additive for a sustainable future, the research has been published in the Journal Sustainable Energy and Fuels. The scientists at KAUST collaborated with Milan Szori and Bela Viskolcz at the University of Miskolc in Hungary.