Sequestration of CO2 discharged from anode by algal cathode in microbial carbon capture cells (MCCs)

Due to increased discharge of CO2 is incurring problems, CO2 sequestration technologies require substantial development. By introducing anodic off gas into an algae grown cathode (Chlorella vulgaris), new microbial carbon capture cells (MCCs) were constructed and demonstrated here to be an effective technology for CO2 emission reduction with simultaneous voltage output without aeration (610 ± 50 mV, 1000 Ω). Maximum power densities increased from 4.1 to 5.6 W/m3 when the optical density (OD) of cathodic algae suspension increased from 0.21 to 0.85 (658 nm). Compared to a stable voltage of 706 ± 21 mV (1000 Ω) obtained with cathodic dissolved oxygen (DO) of 6.6 ± 1.0 mg/L in MCC, voltage outputs decreased from 654 to 189 mV over 70 h in the control reactor (no algae) accompanied with a decrease in DO from 7.6 to 0.9 mg/L, indicating that cathode electron acceptor was oxygen. Gas analysis showed that all the CO2 generated from anode was completely eliminated by catholyte, and the soluble inorganic carbon was further converted into algal biomass. These results showed the possibility of a new method for simultaneous carbon fixing, power generation and biodiesel production during wastewater treatment without aeration.