Microbial Electrosynthesis from CO2 reaches Productivity of 1 Syngas and Chain Elongation Fermentations

Abstract

Microbial electrosynthesis allows the electrochemical upgrading of CO2. However, higher productivities and energy efficiencies are needed to reach a viability that can make the technology transformative. Here we show how a biofilm-based microbial porous cathode in a directed flow-through electrochemical system can continuously reduce CO2 to even-chain C2-C6 carboxylic acids during 248 days. We demonstrate a 3-fold higher biofilm concentration, volumetric current density, and productivity than the state of the art, up to a new record of -35 kA m-3cathode and 69 kgC m-3cathode day-1, at 60-97% and 30-35% faradaic and energy efficiencies, respectively. Most notably, the volumetric productivity resembles those achieved in lab-scale and industrial syngas (CO-H2-CO2) fermentation and chain elongation fermentation. This work highlights key design parameters for efficient electricity-driven microbial CO2 reduction. There is need and room to improve the rates of electrode colonization and microbe-specific kinetics to scale-up the technology. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=114 SRC="FIGDIR/small/579422v1_ufig1.gif" ALT="Figure 1"> View larger version (70K): org.highwire.dtl.DTLVardef@259668org.highwire.dtl.DTLVardef@1b5adedorg.highwire.dtl.DTLVardef@ada588org.highwire.dtl.DTLVardef@4eb23a_HPS_FORMAT_FIGEXP M_FIG C_FIG