UC Berkeley

The valorization of CO₂ to chemicals beyond C_1-2 products is receiving significant interest; however, the direct electrosynthesis of C_n molecules (n > 4) remains a challenge. Here, we present a two-step abiotic-biotic system for upgrading CO₂ into the biopolymer, poly(3-hydroxybutyrate). In the electrolysis system, CO₂ is converted into C₂ oxygenates using a Cu-Ag tandem electrocatalyst. The electrolysis process generates a liquid stream containing ~ 200 mM acetate in a bio-compatible electrolyte. This electrosynthesized acetate is then fed to a bioreactor, where the substrate is upgraded by Cupriavidus necator to biopolymer with a maximum rate of 32 ± 3.5 mg L^-1 h^-1. We further demonstrate the purification of the resulting biopolymer into a powder. The high productivity of the abiotic-biotic system demonstrates its feasibility for sustainable chemical manufacturing.