Characterization of waste bio-oil as an alternate source of renewable fuel for marine engines

Several physical and chemical properties of waste fish oils (FOs) and used cooking oils (UCOs) were of acceptable levels for utilization as renewable fuels in marine engines. However, the relatively high acid number of FOs and its increase with ageing might lead to increased risk of corrosion. The physical properties density and kinematic viscosity, as well as the water content, were measured using different standard methods. Similarly, the acid number, the content of unsaturated fatty acids and the ash content were measured with standard methods. The chemical composition of fatty acids and monoglycerides was measured with a gas chromatograph-flame ionization detector and by Fourier transform infrared spectroscopy. The sulfur and phosphorus contents were measured using inductively coupled plasma-optical emission spectroscopy. Finally, the thermal properties were measured by thermogravimetric analysis while the heat content was measured with an adiabatic oxygen-bomb calorimeter. The results suggest that these locally produced waste stream-based bio-oils have potential as carbon dioxide-neutral fuels. Several properties could be correlated with the fatty acid content of the oils. The results suggested that for waste-derived bio-oils, their earlier history (storage, thermal treatments before waste classification, ageing) affects their suitability as fuels for marine engines.