Comparison of biofuel quality of waste derived oils as a function of oil extraction methods

Fish derived bio-oils have similar properties to petroleum-derived fuel oils and therefore the potential to be an alternative energy source. The quality of bio-oil as a fuel is determined by the quality of the feedstock and processing conditions. Fish oil may have poor cold flow properties due to the heterogeneity of the lipid composition. Different oil extraction methods produce different levels of homogeneity with respect to lipids. In this study, oil was extracted from fish waste via three different processes; modified fishmeal (MFM), supercritical extraction using carbon dioxide (SC-CO2), and soxhlet extraction. The quality of oil extracted (composition, thermal degradation, physicochemical, and flow properties) were compared. The SC-CO2 extracted 91% and the MFM extracted 71% of the total oil contained in the fish waste. The SC-CO2 oil is more than 86 wt% triglycerides, representing a more homogeneous oil than the MFM at 70 wt% and soxhlet at 66 wt%. The free fatty acid (FFA) of SC-CO2 oil is lower than MFM and soxhlet oil, making it a better feedstock for biodiesel production. Polar lipids were most abundant in the soxhlet oil at 22.98 wt%, followed by the MFM oil at 18.35 wt% and SC-CO2 oil at 7.39 wt%. The MFM oil exhibited a shear-thinning non-Newtonian behavior, while the SC-CO2 oil was Newtonian. Overall, the oil from SC-CO2 showed better fuel properties, particularly as a blend and/or replacement for heating oil, than the MFM and soxhlet oil and the process has the potential for a lower environmental footprint.