Hybrid Biological–Chemical Approach Offers Flexibility and Reduces the Carbon Footprint of Biobased Plastics, Rubbers, and Fuels

A critical challenge for the bioenergy research community has been producing drop-in hydrocarbon fuels and chemicals at yields sufficient to compete with their petroleum-derived counterparts. Biological production of highly reduced compounds poses fundamental challenges. Conversely, glucose, xylose, and sucrose can be fermented to ethanol at near-theoretical yields. Just as olefin crackers are often considered a gateway for petrochemical complexes that produce an array of downstream products, catalytic ethanol upgrading can potentially enable an entire biorefining complex able to produce renewable, low-carbon fuels and chemicals. By doping the Ta<sub>2</sub>O<sub>5</sub>/SiO<sub>2</sub> catalyst with different transition metals, we show herein that Ostromyslensky catalysts can be utilized for direct conversion of ethanol to varying ratios of 1,3-butadiene (1,3-BD), dietheylether (DEE), and ethylene. These results are integrated into the first comprehensive analysis of ethanol conversion to 1,3-BD, DEE, and ethylene that incorporates empirical data with chemical process modeling and life-cycle greenhouse gas (GHG) assessment. We find that the suite of products can replace conventional rubber, plastics, and diesel, achieving as much as a 150% reduction in GHG-intensity relative to fossil pathways (net carbon sequestration). Selecting the route with the greatest ethylene and DEE output can maximize total potential emission reductions.