King Abdullah University of Science and Technology, Saudi Arabia
Title: Recycling waste CO2 to valuable resources through microbial electrosynthesis
Pascal Saikaly received his B.S. in Biology (1997) and M.S. in Environmental Technology (2001) from the American University of Beirut (AUB). Then he received his Ph.D. in Environmental Engineering from the University of Cincinnati in 2005 and continued his training as a postdoc at North Carolina State University until 2007. He joined King Abdullah University of Science and Technology (KAUST) in 2010 coming from AUB, where he was an Assistant Professor since 2008. He is currently an Associate Professor at KAUST. His research interests include microbial electrochemical systems, membrane bioreactors, electro-microbiology, and advanced materials for water and energy applications. Professor Saikaly has more than 74 refereed journal articles in the field’s top journals, including Advanced Materials, Scientific Reports, Environmental Science and Technology, Water Research, Frontiers in Microbiology, Applied and Environmental Microbiology and Journal of Membrane Science. He also has over 100 conference presentations and papers.
Anthropogenic and industrial activities have led to a rapid rise in the atmospheric CO2 concentrations leading to increased global warming. A new approach that has emerged in recent years is that of microbial electrosynthesis (MES), which relies on chemolithoautotrophic bacteria that can uptake electrons directly or indirectly (via H2) from the cathode of an electrochemical cell to catalyze the reduction of CO2 into fuels or value-added chemicals. Gas-liquid mass transfer is one of the limiting factors in MES, mainly because of the low solubility of gaseous CO2 in solution. To overcome this limitation, we developed dual-function electro-catalytic and macroporous hollow-fiber (CCPHF) cathodes that act as an electron donor for chemolithoautotrophs as well as a diffusive material to facilitate direct delivery of CO2 gas to chemolithoautotrophs through the pores in the hollow fibers. Using the CCPHF cathode we observed a Faradic efficiency of 77% for the production of CH4 from CO2 through hydrogenotrophic methanogens when CO2 was delivered directly through the pores of the CCPHF cathode, compared to 3% when gaseous CO2 was bubbled into the solution. We also successfully demonstrated that the rates of product formation can be enhanced by using carbon nanotubes (CNTs), which increases CO2 adsorption capability and enhances microbe-electrode interactions. Modification of the CCPHF cathodes with CNTs resulted in 70% increase in acetate production rate from CO2 in MES using the homoacetogenic bacterium Sporomusa ovata. The use of CCPHF cathodes in MES research is a significant breakthrough. The high specific surface area of the CCPHF cathode maximizes the diffusion of CO2 gas, and the high surface-area-to-volume ratio of the CCPHF cathode architecture solves the issue of cathode packing density for large-scale applications. Most importantly, using CCPHF cathodes make the MES process highly attractive for on-site carbon capture and utilization.