3G-biorefinery from olive oil pomace: Biocapture of CO2 from biogas and lipid production

In the primary sector, the roadmap to success lies in enhancing sustainability and advancing process develop ment within the framework of the circular economy. However, sectors such as that of olive oil have difficulty achieving these goals, but the integration of 2G and 3G-biorefineries could allow to overcome these issues. In this work, CO2 of biogas generated from olive pomace was biocaptured by Chlorella vulgaris using a fed-batch strategy, in which biogas was bubbled directly into the culture medium to recover fatty acids with potential use as biofuel substrate. Results showed that the CO2 removal efficiency in fed-batch mode of operation was similar over 14 cycles, being approximately 83.3 ± 2.4 % as an average. Moreover, a methane percentage of 93.09 ± 0.87 % was achieved when the volume of bubbled biogas increased from 1.5 to 4.0 L. The effect of the fed-batch supply of biogas with 20 % CO2 was outstanding on both lipid and fatty acids methyl esters (FAMEs) contents. Compared to the air-fed photobioreactor, lipid and FAMEs productivities increased 5.1 and 4.4 times, while the percentage of FAMEs improved from 55.75 ± 0.93 % to 82.62 ± 1.24 %. Moreover, the lipid profile revealed a high content of saturated and monounsaturated fatty acids.