Biodiesel production from waste salmon oil: kinetic modeling, properties of methyl esters, and economic feasibility of a low capacity plant

Salmon oil directly obtained from salmon silage in a tricanter centrifuge was subjected to homogeneous acid-catalyzed esterification. Alcohol-to-oil molar ratio, catalyst amount, and reaction temperature were varied in order to obtain the kinetic parameters that fit the data satisfactory. A reaction mechanism with four consecutive reactions was considered and the attack of the nucleophile alcohol to the protonated carbonyl substrate was corroborated to be the rate-determining step, in accordance with previous studies in free fatty acids esterification. A kinetic model with 8 independent parameters described with high accuracy the experimental data of 27 reactions with a regression coefficient of 90.94%. Pre-esterified oil was submitted to transesterification and properties of resulting methyl esters were measured. Acidity, peroxide value, viscosity and flash point were acceptable to use as diesel-grade fuel. However, cold flow properties and especially oxidative stability can limit its use as automotive fuel. Finally, a techno-economic analysis was performed and the influence of salmon oil price on the viability of a low capacity fuel production plant was analyzed. (C) 2015 Society of Chemical Industry and John Wiley & Sons, Ltd