Carbon dioxide pressure-induced coagulation of microalgae

Abstract

The move to a low-carbon economy has generated renewed interest in microalgae for the production of biofuels with the potential mutual benefit of wastewater treatment. However, harvesting has been identified as a limiting factor to the economic viability of this process. This paper explores the harvesting of microalgae using high-pressure gas without the addition of coagulants. Coagulation of microalgae under high-pressure gas was found to be an efficient method to separate algae fromsuspension. The critical coagulation pressures (CCPs) for H2 and CO2 were determined to be 6.1 and 6.2 MPa, respectively. The CO2-induced decrease in solution pH positively influenced coagulation rates, without appearing to affect the CCP. This approach could be beneficial for the economic removal of microalgae from solution for the production of both biofuels and biomedical compounds without the addition of nonenvironmentally friendly chemicals.