Scientists have been using frying oil for several years to obtain biodiesel, a biofuel that can replace petroleum derivatives and is less polluting. The problem is to get a pure fluid, as established by European regulations.
"With acidity levels above 2% it is not possible to obtain a biodiesel that meets European specifications", explains the scientist
"The quality of the oil greatly influences the development of biodiesel", explains Jose Aracil, professor of Chemical Engineering at the Complutense University of Madrid (UCM).
In a study published in the journal Fuel, Aracil and his team have determined the level of acidity from which the biofuel obtained can be used in diesel vehicles. "With acidity levels above 2% you cannot get a biodiesel that meets European specifications", explains Aracil.
In addition, the researchers determined the influence of the acidity of the oils used on the monoglyceride, diglyceride and triglyceride content of the biodiesel obtained and compared them with those included in the European standard EN 14214, where these aspects are regulated.
The scientists took into account the oxidation rate of the fluids, that is, how many times they had been used previously. The more they have been used, the worse their quality is, and that affects the purity of the biodiesel.
The highest level of purity of the biofuel was achieved with low temperatures (30 degrees) and a 0.8% concentration of the catalyst - a substance that increases the speed of a chemical reaction. All the frying oils were provided by a waste manager.
Diesel engine fuel
Thanks to these results, to know if an oil is suitable to generate biodiesel, it will be enough to measure its degree of acidity, according to the expert.
The biofuel, produced in a pilot plant installed in the Design, Optimization and Scaling of Industrial Processes laboratory of the UCM, could be used as fuel for vehicles with a diesel engine by meeting the parameters established by the community standard.
"The worst quality ones are used for large engines, such as those for maritime transport," the professor highlights.
Bibliographic reference: Abderrahim Bouaid, Rodrigo Vázquez, Mercedes Martínez and Jose Aracil. “Effect of free fatty acids contents on biodiesel quality. Pilot plant studies ”, Fuel 174, 2016. DOI: 10.1016 / j.fuel.2016.01.018.