Dual production of bioenergy in heterotrophic cultures of cyanobacteria: Process performance, carbon balance, biofuel quality and sustainability metrics

This research evaluated the dual production of bioenergy in heterotrophic cultures of cyanobacteria. Process performance parameters, carbon balance, single-cell oil production, biofuel quality, volatile organic compounds (VOCs) generation, and sustainability metrics and impact indicators were assessed. The results showed biomass productivity of 1.03 kg/m(3)/d. Biomass (63.9%) and VOCs (8.56%) were the main products formed from the conversion of the substrate in the bioreactor. For single-cell-oil production, it is possible to obtain 0.18 kg/m(3)/d of lipid with this bioprocess. It was determined the fatty acid profile and the quality of biodiesel properties, meeting the requirements established by national and international standards. Besides, the 22 volatile compounds identified presented the energy potential of 122,205.00 kJ/kg and a power generation rate of 10,580.5 kg/m(3)/d. From an environmental point of view, the net energy ratio was 0.13, while the eight mid-points impact categories resulted in an ecotoxicity potential of 430.86 CTUe, energy resources of 230.04 MJ, global warming of 171.05 kg CO2 eq, photochemical oxidation of 1.33 kg 0 3 eq, water footprint of 1.08 m(3), acidification of 0.44 kg SO2 eq, eutmphication of 0.13 kg N eq, and ozone depletion of kg 1.83 x 10(-5 )CFC-11 eq, per functional unit of 1 m(3) of the bioreactor, operating for 5 days. Finally, the proposed process can be considered as a promising strategy for renewable energy production from microalgae.