A Sustainable Chemicals Manufacturing Paradigm Using CO₂ and Renewable H₂

The chemical industry must decarbonize to align with UN Sustainable Development Goals. A shift toward circular economies makes CO₂ an attractive feedstock for producing chemicals, provided renewable H₂ is available through technologies such as supercritical water (scH₂O) gasification. Furthermore, high carbon and energy efficiency is paramount to favorable techno-economics, which poses a challenge to chemo-catalysis. This study demonstrates continuous gas fermentation of CO₂ and H₂ by the cell factory, Cupriavidus necator, to (R,R)-2,3-butanediol and isopropanol as case studies. Although a high carbon efficiency of 0.75 [(C-mol product)/(C-mol CO₂)] is exemplified, the poor energy efficiency of biological CO₂ fixation requires ∼8 [(mol H₂)/(mol CO₂)], which is techno-economically infeasible for producing commodity chemicals. Heat integration between exothermic gas fermentation and endothermic scH₂O gasification overcomes this energy inefficiency. This study unlocks the promise of sustainable manufacturing using renewable feedstocks by combining the carbon efficiency of bio-catalysis with energy efficiency enforced through process engineering.