Assessment of microbial electrosynthesis technology for utilizing unpurified CO2 from industrial sources

Abstract

newline Abstract newlineCarbon capture and utilization (CCU) technologies are highly desired to address the issues newlineassociated with industrial CO 2 release into the atmosphere and achieve a circular carbon use newlinecycle. Although the direct use of unpurified industrial CO 2 at point sources minimizes the newlinepurification and transportation costs, its suitability for producing chemicals via different CCU newlinetechnologies remains to be fully assessed. This thesis focused on testing unpurified industrial newlineCO 2 for acetic acid production via microbial electrosynthesis (MES) technology by leveraging newlinethe inherent CO 2 fixation capabilities of anaerobic chemolithoautotrophic microorganisms. The newlineselected industrial sources include breweries, biogas plants, steel processing units, sugar mills, newlineand incineration plants. Considerable microbial growth and acetic acid production were newlineobserved only with brewery CO 2 and biogas in gas fermentation experiments conducted using newlineH 2 and industrial CO 2 as the sole sources of energy and carbon, respectively. Both brewery newlineCO 2 and biogas contained low impurities that showed no substantial detrimental effect on the newlinegrowth of newlineAcetobacterium-dominated newlineenriched newlinemixed newlineand newlinepure Clostridium newlineljungdahlii microbial cultures. In the proof-of-concept MES experiments with brewery CO 2 in newlinebioelectrochemical reactors, the mixed microbial culture outperformed the pure culture in newlineterms of acetic acid productivity due to its robust activity, synergistic microbial interactions, newlineand tolerance to gaseous impurities. At an E cell of 2.9 V, up to 7.6 ± 0.65 g/L acetic acid was newlineproduced at a rate of 0.5 ± 0.03 g/L/d in the MES reactors operated with 0.7 L/d brewery newlineCO 2 feed under catholyte recirculation conditions. It was achieved at 92 ± 4% and 34 ± 2% newlinefaradic and energy efficiencies. With raw biogas feed containing ~60% CH 4 and ~30% CO 2 , newlineMES produced methane-rich (gt90%) off-gas and acetic acid in the same process. The follow- newlineup process validation and scalability assessments conducted in liter-scale reactors suggeste