Sustainable biorefining of Chlorella vulgaris into protein, lipid, bioethanol, and biogas with substantial socioeconomic benefits

An integrated biorefinery was developed that utilizes microalgal biomass, Chlorella vulgaris, to sustainably produce proteins, fatty acids, bioethanol, and biogas. The microalgal soluble proteins and fatty acids were initially extracted through a cascading extraction process, including bead milling and solvent extraction. Subsequently, the investigation focused on utilizing the biomass residues for bioethanol and biogas production, ultimately improving energy recovery. Implementing the cascading process resulted in a 25 % enhancement in bioethanol yield and a 22.4 % increase in biomethane yield compared to untreated biomass. This approach resulted in 78.0 g of protein, 50.9 g of lipid, 20.8 ml of ethanol, and 136.5 L of methane from one kilogram of dry C. vulgaris biomass. Considering the potential of 8,640 k tons of annual microalgae production in Iran, an estimated 4.1 million tons of CO2 emissions could be averted. This reduction could result in saving approximately 1394.8 million USD in associated social costs of carbon. These improvements in fully valorizing biomass through practical cascading methods significantly advance microalgal biorefinery.