From oil refinery to microalgal biorefinery

• The developing a microalgae biorefinery has been assessed.
• The wastes generated by the oil refineries were used to bioproducts production.
• The production of bioenergy was considered.

The objective of this study was to develop an integrated system of biotransformation of carbon dioxide in oil refineries. The liquid and gaseous wastes from oil refining were considered for the cultivation of Aphanothece microscopica Nägeli in a bubble column photobioreactor. Growth kinetics, carbon dioxide removal and oxygen release rates, carbon balance, lipid production and biofuel quality were determined. The results showed the potential use of oil refinery wastes in microalgae-based systems under optimized culture conditions. The maximum specific growth rate was 1.4 day−1 and the maximum carbon dioxide elimination capacity was 22.9 mg/L min. Each CO2 mass unit bioconverted resulted in approximately 0.75 O2 of mass units released. Carbon balance analyses indicated that a small fraction (3.64%) of the carbon dioxide is fixed into a biomass form. Volatile organic compounds (92.0%) were the main products of carbon dioxide transformation in the photobioreactor, in such conditions. For the production of biodiesel, it is possible to obtain 0.08 glipid/L day with this process. The quality properties of the biodiesel were an ester content of 99.7%, a cetane number of 51.3, an iodine value of 79.9 gI2/100 g, a degree of insaturation of 65.3% and a cold filter plugging point of 24.9 °C. Based on these results, the process developed could be considered a promising emerging biorefinery platform of waste-material-utilization type.

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