Recycling of kebab restoration grease for bioenergy production through acoustic cavitation

Abstract The use of renewable energies to combat climate change is one of the greatest goals for humanity. To achieve this objective, one alternative is to valorize and recycle wastes, i.e. food waste, generated daily due to our way of life. Every day, human beings generate thousands of tons of this organic matter that can be recycled to produce bioenergy. Food waste is a source of carbon that must be included into the carbon dioxide cycle. In this manuscript, we propose to recycle the organic waste produced in a kebab local restaurant through biodiesel production, assisted by clean energy i.e. ultrasound. Biodiesel of both chicken grease and a mixture of beef-lamb were synthesized and optimized by response surface methodology and desirability function. Fatty acid methyl ester yields were higher (97.42% w/w for chicken grease and 96.98 for beef-lamb grease) than the minimum threshold established by European regulation EN 14214 (≥96.5% w/w). Although, cold-filter plugging point and oxidation stability resulted in values far from those established by the EN 14214 standard. To improve them while meeting standard threshold, both antifreeze and antioxidant were added following a design of experiments. The addition of antioxidant t-butyl-hydroxyquinone (TBHQ) at concentrations between 800 and 900 ppm and a commercial antifreeze at concentrations above 0.08% v/v, significantly improved biofuel quality in terms of storage and cold flow properties. We can conclude that animal fat residues from kebab restoration can provide suitable biodiesel if antioxidants and antifreezes are added.