Extraction of bio-oil via wet based from Nannochloropsis oculata

Current research has shown a great interest in microalgae due to its ability to capture CO2 from the atmosphere, a harmful gas to the environment, and to store a high added value oil. However, the extraction of the oil from microalgae represents a stage of high energy demand, and it is necessary to develop a viable process in this aspect. In this context, the present work aims to extract the bio-oil from the microalga of the species Nannochloropsis oculata via humid base, in order to remove the drying step of the extraction process. For this, an experimental planning of the factorial type (3²) with two central points was used, totalizing 11 experiments for each solvent (ethanol and hexane). The variables studied in the planning were the time of application of the ultrasound and the time of extraction by Soxhlet. As a result, extraction with the application of ultrasound for 60 min, followed by Soxhlet for 8 h with hexane showed better yield (20.29%) of bio-oil. The production of bio-oil under the same conditions with ethanol was 16.83%. The lowest energy expenditure in relation to the production of 1 g of oil occurred under the conditions of application of 60 min of ultrasound and 4 hours of solid-liquid extraction. The energy expenditure was also compared to the dry and wet basis with the two solvents. In the dry base extraction, the yield was lower than the wet basis. By the analysis of GC-MS it was observed that drying influences the profile of fatty acids, reducing the percentage of monounsaturated and polyunsaturated fatty acids. It is concluded that the wet basis extraction is the best option, since drying deteriorates the bio-oil and does not influence significantly the yield of the bio-oil.