Assessment of continuous catalyst-free production of ethyl esters from grease trap waste

Continuous production of fatty acid ethyl esters (FAEE) from grease trap waste (GTW) in a catalyst-free medium and using pressurized ethanol was evaluated. For this purpose, the lipid fraction was previously separated from GTW, characterized, and used to conduct the reactions, which evaluated the effect of the operational variables to maximize the formation of FAEE. The results obtained indicate that GTW lipids present the oleic and linoleic acids as major in their composition, besides a high content of free fatty acids. It was observed that the higher availability of ethanol in the reaction medium gave the achievement of higher yields. Similar effect is observed for the variables temperature and pressure. However, at temperatures >300 °C fatty acids degradation occurs, with the decrease in FAEE yield. For the one-step reaction, the maximum FAEE yield was ∼93% obtained at 300 °C, 20 MPa, oil to ethanol mass ratio of 1:2 and 30 min. The two-step reaction increased yield to ∼96%.