Fuel properties comparison of species of microalgae and selected second-generation oil feedstocks

Comparative investigation and assessment of microalgal technology as a biodiesel production option was studied alongside other second generation feedstocks. This was carried out by comparing fuel properties of species of Chlorella vulgaris, Duneliella spp., Synechococus spp. and Senedesmus spp. with the feedstock of Jatropha (ex-basirika variety), Hura crepitans, rubber and Natal mahogany seed oils. The microalgae were cultivated using a photo-bioreactor (New Brunsink set-up model BF-115 Bioflo/CelliGen made in the USA) with operating parameters: 14 l capacity, working volume of 7.5 l media, including 10% inoculum, at optical density of 3.144 @ 540 nm and light intensity of 200 lux, for 23 and 16 days respectively. Various produced/accumulated biomasses were harvested by draining, flocculation, centrifugation and drying, and then subjected to lipid extraction processes. The oils extracted from the algae and feedstocks were characterised and used to produce biodiesel fuels, by the transesterification method, using a modified optimisation protocol. The fuel properties of the final biodiesel products were evaluated for chemo-physical and fuel properties. Results revealed Chlorella vulgaris as the best strain for biomass cultivation, having the highest lipid productivity (5.2 mgl(-1)h(-1)), the highest rate of CO2 absorption (17.85 mgl(-1)min(-1)) and the average carbon sequestration in the form of CO2 was 76.6%. The highest biomass productivity was 35.1 mgl(-1)h(-1) (Chlorella), while Senedesmus had the least output (3.75 mgl(-1)h(-1), 11.73 mgl(-1)min(-1)). All species had good pH value adaptation, ranging from 6.5 to 8.5. The fuel properties of the microalgal biodiesel in comparison with Jatropha, rubber, Hura and Natal mahogany were within ASTM specification and AGO used as control. Fuel cultivation from microalgae is feasible and will revolutionise the biodiesel industry.