Electrochemical-biological hybrid conversion of captured carbon dioxide to bioproducts

CO₂ is a promising C1 feedstock for the sustainable production of fuels, chemicals, and materials, but its efficient conversion into value-added products remains challenging. Biological CO₂ conversion provides high selectivity and access to structurally complex products under mild conditions, yet is limited by low productivity, gas-liquid mass transfer limitations, and the need to balance carbon fixation, reducing-power generation, and product formation. Electrochemical-biological hybrid systems can mitigate some of these constraints by supplying cathodic reducing equivalents or assimilable CO₂-derived intermediates for microbial or enzymatic upgrading. This review examines enzymatic and microbial CO₂ conversion platforms and classifies hybrid systems by electron-transfer mode, process configuration, intermediate type, and target product. Reported systems are compared across five product classes: microbial biomass and single-cell protein, monomers and biopolymers, organic acids and small molecules, fatty acids and lipids, and alcohols and biofuels. Most studies remain at the laboratory scale, and further progress requires improved electrochemical output concentration and purity, C1/C2 assimilation, redox balancing, host tolerance, and reactor compatibility. Overall, development of these systems will depend on matching electrochemical outputs and process configurations with the metabolic and redox requirements of target products, rather than optimizing the two modules independently.