Comparative Assessment of Biodiesel Produced from Microalgae, Used Vegetable Oil and Fossils (Published)
Biodiesel was produced from two sources; microalgae oil and used vegetable oil and compared with conventional fossil diesel. The microalgae were collected from an open pond where they constitute nuisance while the used vegetable oil was gotten from roadside fried food sellers as waste products. Trans-esterification was carried out to give the corresponding mono alkyl ester (biodiesel). Quality assessment of the biodiesel produced was carried out via determination of chemical characteristics; Density, viscosity, flash point, pour point and acid value. The density of the biodiesel from the two sources were 0.882 kg. L-1 and 0.870 kg. L-1 respectively and higher than the conventional diesel. Flash points of the biodiesel produced from microalgae (1650C) and used vegetable oil (1810C) were significantly higher than the conventional diesel. Pour points of the biodiesel produced from microalgae oil and used vegetable oil were -100C and -150C respectively while viscosity values at 350C were 5.2 and 4.5 respectively. The acid value of the biodiesel produced from the microalgae oil (0.394) and the used vegetable oil (0.290) were lower than that of the conventional diesel fuel (0.5). The chemical characteristics of the biodiesel produced were in line with standard specifications. The biodiesel produced when compared with the conventional diesel fuel based on their different parameters may be fit and greener replacement for fossil diesel fuels, which are nonrenewable and not biodegradable.
The main aim of this project was to undertake a feasibility study of microalgae biodiesel production from the Cambois peninsular, Northumberland England. This particular project site was chosen for its potential to support microalgae growth i.e. close proximity to both water and CO2 source. Microalgae chlorella specie was chosen for this analysis because of its good productivity (22g m-2 day-1) as well as high lipid content (50% dry weight). The analysis considers 150 days farm production (March to August) due to low temperature in the winter. A comparative analysis of foam column microalgae harvesting process followed by oil extraction through in-situ transesterification was undertaking against the conventional centrifugation-harvesting route followed by conventional tranesterification. Lastly a hybrid of the 2 processes of centrifugation followed by in-situ transesterification was also analysed side by side.
The 3 different biodiesel processing routes were examined based on final biodiesel yield, cost and energy consumption. The centrifugation route provides high biodiesel yield of 115 L ha-1 day-1 but with associated high energy and centrifuge installation cost. Foam column separation yield 110 L ha-1 day-1 with optimum power consumption and installation cost. The hybrid system yield 100 L ha-1 day-1 with minimum power consumption but may suffer set back due to high cost of centrifuge cost and maintenance. The best-case scenario of foam column separation process was further evaluated to validate its economic potential for large-scale biodiesel production as against the current price of fossil diesel. The outcome confirms the potential of microalgae biodiesel to be cost competitive with diesel if the harvesting process is substituted with the foam column separation technique, while the traditional oil transesterification be substituted with the in-situ transesterification technique.